RESEARCH

~T~~Q~I IIiIIAGRICULTURAL EXPERIMENT STATION EAST LANSING

APRIL 1978

ANNUAL BLUEGRASS (poa annua L.)DESCRIPTION, ADAPTATION, CULTURE AND CONTROL

BY J. B. Beard, P. E. Rieke, A. J. Turgeon, and J. M. Vargas, Jr.

TABLE OF CONTENTSPage

INTRODUCTION 3PLANT DESCRIPTION 4TAXONOMY AND CYTOGENETICS 5ORIGIN AND DISTRIBUTION 5CLIMATIC ADAPTATION 6EDAPHIC ADAPTATION 9PESTS 10

Diseases 10Insects 12Nematodes 14

PROPAGATION 14TURFGRASS COMMUNITY DYNAMICS ISCULTURAL PROGRAM FOR ANNUAL BLUEGRASS TURFS 18

Greens I 8Fairway and Sport Fields 19

CONTROL OF ANNUAL BLUEGRASS 19Cultural. 19Chemical 20

CURRENT STATUS OF HERBICIDES FOR ANNUAL BLUEGRASS CONTROL 23LITERATURE CITATIONS 26

Cover: Annual bluegrass is the predominant turfgrass species found on fairwaysand tees on many golf courses in the cool humid region of the U.S. Continuingresearch, such as in the field plots shown, is needed to understand more fully thescience and practice of optimum annual bluegrass maintenance. (Photos-P. E.Rieke)

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ANNUAL BLUEGRASS(Poa annua L.)DESCRIPTION, ADAPTATION, CULTURE AND CONTROL

BY J. B. Beard, P. E. Rieke, A. J. Turgeon, and J. M. Vargas, Jr. *

*Former Professor, Michigan State University, now Professor, Texas A & MUniversity; Professor, Michigan State University; former Instructor, MichiganState University, now Associate Professor, University of Illinois; Associate Pro-fessor, Michigan State University, respectively.

ACKNOWLEDGEMENTS

Extensive investigations of annual bluegrass were con-ducted at Michigan State University by the four authorsfrom 1965 into the early 1970's. A major portion of the in-vestigations concerning the description, adaptation, and cul-tural practices affecting annual bluegrass growth and de-velopment were supported by a series of grants from theUnited States Golf Association Green Section Research andEducation Fund, Inc. Much of the information derived fromthese studies served as the data from which this bulletin hasbeen prepared.

The authors would also like to acknowledge the assistanceof the Agronomic staff of the Green Section of the UnitedStates Golf Association, W. H. Bengeyfield, W. G. Bu-chanan, J. B. Moncrief, A. M. Radko, C. Schwartzkopf, S. J.Zontek, and two former staff members, F. L. Record and H.M. Griffin for their comments and review of this manu-script. Their recommendations on the culture of annualbluegrass served as the basis for preparing the Section onCultural Programs for Annual Bluegrass Turfs.

INTRODUCTION

Annual bluegrass is a factor in the culture of mostirrigated sport~ turfs and ornamental lawns either as(a) a weed to be controlled or (b) a substantial compo-nent of the turfgrass community that must be con-sidered when selecting the appropriate long-term cul-tural program. In 1937, Sprague and Burton (100)published the only other bulletin on annual bluegrassand its growth requirements. Their objectives were,"to determine the conditions under which the speciesmakes its most satisfactory growth, and also the fac-

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tors responsible for its unwanted invasion of turfareas and replacement of preferred grass."

The objectives of this publication are essentially thesame plus a review of chemical control options avail-able. The cultural conditions and framework in whichannual bluegrass is grown in the 1970's are much dif-ferent than the 1930' s. These changes' incl ude (a)more intensive use of irrigation and great advances insophisticated irrigation systems; (b) increased fertilitylevels, particularly nitrogen; (c) substantial improve-ments in the turfgrass cultivars utilized in sports andornamental turfs; (d) major improvements in theequipment utilized in mowing and cultivating turfs;and (e) the development of selective preemergenceherbicides, numerous organic systemic and non-sys-temic fungicides, and a wide range of organic insec-ticides. A publication is needed which updates andsummarizes the existing knowledge of annual blue-grass as it relates to turfgrass culture.

Although annual bluegrass has served as the basisfor many articles in trade publications and conferenceproceedings over the years, the amount of valid pub-lished data is rather limited. Most of the scientificliterature reported has been concerned with methodsof controlling annual bluegrass. Investigations con-cerning the description, adaptation, establishment,and culture of annual bluegrass are quite limited. It isin this latter area that the authors have concentratedtheir annual bluegrass research during the past 10years.

The authors have reviewed the existing literaturethat is based on sound experimental investigationsand placed it in context with modern turfgrass cul-ture. Where information is lacking, this will be in-dicated. Hopefully, this approach will stimulate fur-ther investigations of annual bluegrass. Specific factswill be supported by literature citations. This com-prehensive bulletin on annual bluegrass should serveas the basic reference source for both turfgrass re-searchers and laymen in either the control or cultureof annual bluegrass.

PLANT DESCRIPTION

Seedhead CharacteristicsThe morphological description of the annual blue-

grass seedhead as given by Hitchcock and Chase (59)is as follows:

"Panicle pyramidal, open, 3 to 7 cm long;spikelets crowded, 3- to 6-flowered, about 4mmlong; first bloom 1.5 to 2mm, the second 2 to2.5mm long; lemma not webbed at base, dis-tinctly 5-nerved, more or less pubescent on thelower part of the keel sometimes simulating aweb; anthers 0.5 to 1mm long."Characteristics of the annual bluegrass inflorescence

are illustrated in Fig. 1. This description is based onan unmowed sward. The overall size of the panicle isproportionally reduced as the cutting height islowered. Annual bluegrass is capable of forming aninflorescence and producing viable seed even at a6mm height of cut.

Fig. 1. Panicle (left) and floret (right) of annualbluegrass. (Photo-A. J. Turgeon)

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:.'...•..=.' ..~~ ..c ••--- ..-.,.~ .•'.:.'. __ •. - - .. !..../..-.\...'l........... - .. _ .. -, ...... _ ..~~.. ;~".=-';.' '-':-"=. :.c- ~-~.- :;-~_.; .~-" .., •i': I

Fig. 2. Vegetative characteristics used in the iden-tification of annual bluegrass: Shoot (right), ligule (up-per left), and leaf apex (lower left). (Photo-A. J.Turgeon)

Vegetative CharacteristicsFrequently vegetative characteristics must be used

in identifying annual bluegrass under mowed turfconditions, because the inflorescence is not alwayspresent. This description is presented with the recog-nition that some variation can occur, depending onthe particular strain of annual bluegrass present andthe environmental conditions on the site. The vegeta-tive description of annual bluegrass given by Beard(12) is:

"vernation folded; sheath distinctly compressed,glabrous, whitish at base, keeled, split with over-lapping hyaline margins; ligule membranous,1-3mm long, thin, white, acute, entire; collarconspicuous, medium broad, glabrous, dividedby the midribs; auricles absent; blades V-shaped,2-3mm wide, usually light green, glabrous, soft,boat-shaped apex, transparent lines on eachmidrib, parallel sided, flexuous transversely,margins slightly scaborus and hyaline; stems flat,erect to spreading sometimes rooting at thenodes and forming stolons."Detailed drawings of some of these vegetative

characteristics are shown in Fig. 2. It should benoted that both the noncreeping bunch type and thestoloniferous pro~trate growing type of annual blue-grass may occur in turfs (Fig. 3)1. This is in contrastto the classical description of annual bluegrass thathas been based on nonturf conditions. Actually, awhole range in growth habits occurs rather than justthe two extremes. The upper leaf surface has a thin-ner cuticle layer and greater stomatal density thanthe lower surface (16).

The vegetative characteristics most commonly usedin identifying annual bluegrass under turf conditionsinclude: vernation f~lded in the bud shoot, long

lFigs. 3a and 3b are color pictures located on the inside backcover.

transparent ligule, V -shaped cross section of the leafblade, and boat-shaped leaf tip. Supporting character-istics that may occasionally be helpful include thepresence of seedheads and a turf which tends to besomewhat yellowish green to light green.

Turf CharacteristicsUnder the close cut, irrigated turfgrass cultural con-

ditions now being utilized, annual bluegrass is cap-able of forming a dense, uniform quality turf of in-termediate leaf texture (12 and 91). Both the densityand fineness of the leaves increase as the cuttingheight is reduced from 5 to 0.6cm. Annual bluegrassis a low growing diminutive plant possessing rootingdepths comparable to Kentucky bluegrass and bent-grass.

This is contrary to what has been written in the un-documented literature where it is considered to be in-herently shallow rooted. Unfortunately these infer-ences are drawn primarily from annual bluegrassgrowing in compacted soils where Kentucky bluegrassand bentgrass can not persist. Experiments wherethese three species are compared under similar mow-ing, fertility, and soil conditions reveal the capabilityof annual bluegrass to possess root growth depthssimilar to the other two species (100 and 115).

Annual bluegrass turfs tend to be somewhat lightgreen sometimes even greenish-yellow in appearance(12 and 91). When annual bluegrass occurs as scat-tered clumps in bentgrass, bluegrass, or bermudagrassturfs it tends to disrupt the color of the turf due tothis lighter green color. Color should not be used asone of the major characteristics in identifying annualbluegrass, because exceptions occur.

TAXONOMY AND CYTOGENETICS

Poa annua has been classified as a tufted, bunchtype annual in the past. Common names used in vari-ous parts of the world include annual bluegrass, an-nual meadowgrass, and wintergrass. It is cross-pollin-ating with a somatic chromosome number of 28 (13,77, 78, and 80). Although previously considered anannual it will persist under close cut, irrigated situa-tions as a prostrate creeping perehnial that roots atthe nodes.

Close examination of aimual bluegrass turfs revealsnumerous types ranging from (a) the classical tufted,bunch type annual having. a characteristic uprightgrowth habit, prolific seed production, and strongseed dormancy to (b) a creeping perennial that rootsat the nodes of prostrate stolons and tillers, hasrestricted seed production potential, and minimal seeddormancy (10, 11, 67, 62, 63, 64, 65, 103, III and117). The former has been given the subspecies classi-

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fication of Paa annua var. annua L. Timm, and thelatter perennial type subspecies classification of Poaannua var. reptans (Hauskins) Timm.

The annual types have lower leaf and node num-bers, less secondary tillers, and fewer adventitiousroots than the perennial types (46). Actually there aremany intermediate types between these two extremeseven though annual bluegrass is cross-pollinated butapomictic (13, 78, 110 and 111). Although Hovin (64and 65) concl uded that the most common type of an-nual bluegrass in the United States was the uprightannual, Gibeault (46) found a high proportion ofperennial types in samples collected in Oregon andWashington. He determined that the presence of an-nual or perennial subspecies in a turf could be cor-related with the watering regime. Areas that werewatered infrequently or not at all have mainly annualtypes, while the perennial subspecies could be antic-ipated in more frequently irrigated turfs.

Youngner (117) found perennial types of annualbluegrass in golf greens that persisted for severalyears. They had formed distinct, uniform patches thatprobably developed from individual seedlings. He col-lected clones of these biotypes which were then prop-agated and maintained at a 0.6cm (0.25 inch) cuttingheight. These turfs persisted, but were severely dam-aged in the summer by disease-causing organisms, es-pecially Pythium.

Eventually, a fertile, amphidiploid selection devel-oped off-type plants while two sterile, amphihaploidselections remained true-to-type. Thus, annual blue-grass is a highly variable species which can adapt towidely differing environmental conditions by naturalselection for existing biotypes, or by the developmentof new biotypes through cross-pollina tion betweengenetically different plants. The additional capabilityof continual reseeding of occupied sites ensures aprominent role for annual bluegrass in intensivelycultured turfgrass communities.

ORIGIN AND DISTRIBUTION

Annual bluegrass is a native of Europe and is be-lieved to have originated from a cross between Poainfirma H. B. K., an annual species, and Poa supinaSchrad., a creeping perennial (111). According toHitchcock and Chase (59), annual bluegrass is foundfrom Newfoundland and Labrador west to Alaska,south to Florida and California, and in high altitudesin tropical America. Gibeault (46) reports its occur-rence in Australia, South America, North Africa, andNorth Asia, in addition to Europe.

Tutin (11l) suggested that it is usually limited toareas of human habitation and Hovin (63 and 65)postulates that it was introduced to America by the

TURFGRASS CLIMATIC ZONES

Fig. 4. Turfgrass Climatic Zones.

early Spanish explorers. It is apparent from the widerange of reports that annual bluegrass is widely dis-tributed throughout the temperate and sub-tropicalregions of the world, particularly where the presenceof man tends to be dominant.

A map of turfgrass climatic zones in the UnitedStates is shown in Fig. 4. In the warm-humid, semi-arid and warm-arid regions, annual bluegrass maybehave as a winter annual; while in the more north-erly portions of the cool-humid and cool-arid regionsit may behave as a summer annual. In contrast, theperennial creeping types may persist as perennials inclosely mowecl, irrigated, fertilized turfs for manyyears in the warmer portion of the cool-humid cli-mate and cooler portions of the warm-humid climate-unless subjected to unusual heat, cold, drought, orwea r stresses.

CLIMATIC ADAPTATION

Each of the major aspects of climatic adaptation-temperature, water, light, and atmospheric factors-will be discussed individually based on the limited in-formation available. However, remember that specificplant responses are not determined by one single en-vironmental factor, but by the levels and interactionamong all components of the environment impingingon the annual bluegrass plant over both short-termacute and long-term chronic exposures.

Annual bluegrass is a cool-season species that be-haves as a winter annual in warm climates. Maxi-mum root production occurs at 18 to 21 C (65 to70F), depending on the subspecies involved (17 and58).

Seedhead development is most rapid at 27C (80F)and is substantially reduced at lower temperatures(17). The optimum temperature in terms of overall

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turfgrass performance and quality is in the range of16 to 21C (60 to 70F) since it gives a more moderateshoot growth rate. It is more important to maintain afavorable temperature for root growth since theshoots can survive greater temperature extremes, par-ticularly heat, without significant detrimental effectsto the annual bluegrass plant.

Annual bluegrass growth declines and eventuallyceases as temperatures are increased or decreasedfrom the optimum. It is quite prone to injury or com-plete kill from heat or cold stress in comparison tosuch commonly used cool season turfgrasses as creep-ing bentgrass and Kentucky bluegrass.

Heat StressAs temperatures increase above 21 C (70F), the fol-

lowing series of growth responses are observed: Theroots of annual bluegrass begin to turn a distinctbrownish color at 27C (80F) or above, indicating areduction in normal functions. Individual plants alsoreach maturity much more rapidly as temperaturesare increased above 27C (80F) (17). Annual bluegrassplants mature and die quite rapidly in the tempera-ture range 30 to 35C (85 to 95F) (21, 25 and 58).

Lethal heat stress of annual bluegrass occurs attemperatures near 40C (l04F) (40). These tests wereconducted in a controlled environment under near100 % humidities so that a known leaf temperaturecould be produced without interference from trans-pirational cooling activity. The first heat injury symp-toms appear on annual bluegrass at the junction ofthe leaf sheath and the leaf blade of the second andthird youngest leaves (Fig. 5).

The actual lethal temperature will vary with theduration of exposure. For example, two hours expo-

Fig. 5. Heat injury symptoms in annual bluegrass asshown by a cross-section a t the junction of the leafsheath and leaf blade at the second youngest leaf.(Photo- J. B. Beard)

sure to 42C (108F) under 100 % humidity conditionsresulted in complete kill of annual bluegrass plants;while 10 hours exposure to 38C (lOOF) at near 100%~umidity was lethal. A distinct series of degradation>rocesses occurs during heat stress including: proto->lasmic granulation, followed by coagulation against(he cell wall, cell wall breakdown, and eventuallytotal collapse of the cell wall (40).

Low Temperature StressAs soil temperatures are decreased below 10C

(SOF), annual bluegrass shoot growth is reduced,eventually ceases at lower temperatures, and subse-quently enters winter dormancy. Annual bluegrass ismore prone to low temperature kill than Kentuckybluegrass or creeping bentgrass (7) (Fig. 6)2. A longi-tudinal section through the crown of an annual blue-grass plant (Fig. 7)2 shows that the lower portion ofthe crown responsible for initiating the root system iskilled a t slightly higher tempera ture than the upperportion of the crown responsible for initiating shootgrowth (5).

The specific killing temperature varies with thehydration level of the tissue as well as seasonally (7).For example, annual bluegrass which has been al-lowed to harden in late fall to a crown moisture con-tent of 78 to 80 % will be killed from a S-hour soiltemperature exposure at -20C (-SF); while in earlyspring prior to spring greenup, annual bluegrass iskilled by a S-hour soil temperature exposure at -lSC(SF) (Table 1). Annual bluegrass growing on poorlydrained sites is particularly prone to low temperaturekill (8 and 21).

Ice CoversIce covers are a potential stress problem on annual

bluegrass turfs during the winter period. However,

the potential for kill by ice covers is not nearly asgreat as by direct low temperature kill. More com-monly, annual bluegrass turfs can be readily killed inlow areas where standing water occurs prior to freez-ing, or during thawing of ice causing increased crownhydration followed by lethal low temperature stress(Fig. 8)2.

If exposed to long periods of ice coverage, which isa rare occurrence, annual bluegrass is substantiallymore susceptible to kill than Kentucky bluegrass orcreeping bentgrass (6). For example, when subjectinglow temperature-hardened annual bluegrass turfs toextended periods of ice coverage at -32C (-26F), theywere uninjured after 60 days, 20% thinned after 75days, and could be killed after 90 days of ice cover-age (Fig. 9).

Fig. 9. The comparative tolerance to 105 days icecoverage at -3C(26F) of Toronto creeping bentgrass(left), Merion Kentucky bluegrass (center) and annualbluegrass (right). (Photo- J. B. Beard)

2Figs. 6, 7 and 8 are color pictures located on the inside backcover.

Table 1. The seasonal variation in proneness to lowtemperature kill of annual bluegrass when exposedto five temperature levels for 5 hours.

Percent low temperature killDec. April June

5 10 5

Temperaturetreatment°C(OF)

-6 (20)-9 (15)-12 (10)-15 (5)-18 (0)

ooo5

70

2357095100

65100100100100

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Spring Green-upOverwintering annual bluegrass plants can initiate

growth at about 13C (SSF), while for creeping bent-grass and Kentucky bluegrass new growth occurs atsomewhat lower temperature in the range of 10C(SOF) (17). This might suggest that early spring nitro-gen fertilization while temperatures are still cool,should enhance the competitive ability of the lattertwo species when they occur in a polystand comparedto annual bluegrass. However, there are nontechnicalreports that annual bluegrass is one of the earliestgrasses to initiate growth in the spring. It has beensuggested that the early spring green-up is due togermination of annual bluegrass seeds in small openareas of bare soil in the turf which warm up morerapidly in the spring encouraging germination.

WaterMoist to wet soil conditions are particularly favor-

able for annual bluegrass growth and actually en-hance its competitive position. However, annual blue-grass is much more readily injured from internalplant water deficits created by either atmospheric orsoil drought than other perennial cool season speciessuch as Kentucky bluegrass and creeping bentgrass(l0, 11 and 21). Under soil drought, annual bluegrasscannot readily make the appropriate physiological ad-justments in terms of: increased carbohydrate ac-cumulation, alteration of protein characteristics to anincreased bound water content, and the subsequentdecrease in the tissue moisture content, plus an in-creased capability to bind the remaining moisturewithin the plant tissues.

The physiological processes occurring during coldand drought stress are quite comparable. Measure-ments of crown water content during cold hardeningreveal that the bentgrasses are capable of a lowerrelative water adjustment of as much as 20% and theKentucky bluegrass of approximately 5%, while an-nual bluegrass will have little change (7).

The potential for water stress tends to influence theoccurrence of certain annual bluegrass subspecies.The prostrate creeping biotypes tend to dominatewhere moisture stress conditions are minimal. The an-nual bunch biotypes, through their drought escapemechanism, tend to be dominant in regions subjectedto periodic moisture stress (46). Annual bluegrass isalso quite prone to winter desiccation compared toother cool season turfgrasses. This is attributed to itsinability to readily harden into a physiological condi-tion where it has increased capability to hold mois-ture within the tissues against a strong outward gra-dient.

Fig. 10. The comparative tolerance of annual blue-grass to submersion after 2, 3, 4, and 5 days at a30C(86F) water temperature. (Photo-J. B. Beard)

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Annual bluegrass is well adapted to wet soil condi-tions, but it is not equally tolerant to water submer-sion when compared to the other commonly used coolseason turfgrasses. Toronto creeping bentgrass rankssuperior in submersion tolerance; Kentucky bluegrassis in a comparable range and red fescue is substantial-ly less tolerant of extended submersion (Fig. 10).

The water temperature strongly affects proneness toinjury from submersion. For example, annual blue-grass is killed in approximately 5 days at watertemperatures of 30e (86F), while it requires 20 daysof exposure at water temperatures of 20e (68F) formore than 50 % kill to occur and only 15% injury oc-curs after 20 days exposure to water at a temperatureof 10e (50F). In contrast, exposure to water tempera-tures above 40e (l04F) will result in kill within amatter of minutes (9).

LightMaximum growth in annual bluegrass occurs at

high light intensities and longer photoperiods as longas heat or moisture stress are not associated withthese higher light levels (71). Annual bluegrass is alsowell adapted to shade, most probably due to thecooler temperatures associated with this environment.It is frequently observed growing in densely shadedareas where other turfgrass species have not been ableto persist (l00). This is partially attributed to its abil-ity to escape environmental stresses associatedtwithshaded areas by producing seeds which remain dor-mant in the soil until conditions are favorable forgermination and growth. The annual bunch biotype,which is capable of prolific seedhead production, iswell adapted to this situation, but the creeping peren-nial biotypes do not have this ready regenerativecapability.

Annual bluegrass has a strong light requirement forseed germination compared to Kentucky bluegrassand creeping bentgrass (89 and 32). Thus, densestands of turf which shade the soil surface are capableof preventing annual bluegrass seed germination andinvasion. However, openings in the turf resulting fromdisease damage, divots, or similar adverse stress con-ditions will permit light penetration to the surface.The result is rapid germination of the existing annualbluegrass seeds followed by seedling growth and inva-sion of the area (10 and 11). In terms of the photo-period requirement for maximum floral induction, an-nual bluegrass is classified as a short photoperiodplant. That is, it responds most favorably in terms ofseedhead induction to day lengths of less than 12hours (71 and 104).

In addition, annual bluegrass has the ability to con-tinue flower induction and development throughout

the remainder of the growing season over a widerange of photoperiods. Seedhead development is usu-ally most intense during the late spring and earlysummer period, but the original floral induction oc-curred the previous fall under cool, short-day condi-tions.

Atmospheric PollutantsAnnual bluegrass is more prone to injury from at-

mospheric pollutants than most of the commonly usedcool season turfgrasses. Its susceptibility to smog, inthe form of peroxyacetyl nitrate and ozone, is par-ticularly high (l6). So much so that this plant hasbeen used in Los Angeles as a biological indicator ofacute smog exposure. This high susceptibility toperoxyacetyl nitrate and ozone injury can cause prob-lems in the culture of annual bluegrass in denselypopulated urban centers. It is already a problemalong the east and west coasts of the United Stateswhere these two atmospheric pollutants are signifi-cant, persistent problems.

Sulfur dioxide is another atmospheric pollutant thatmay occasionally cause problems, particularly in in-dustrialized urban areas where high sulfur coal andoil are burned. Annual bluegrass ranks intermediatein susceptibility to sulfur dioxide injury, while creep-ing bentgrass and red fescue are particularly sensitiveand bermuda grass is relatively insensitive (1 and 3).Finally, toxic fluoride gases such as hydrogen fluorideand silicone tetrafluoride may be occasional problemsin the immediate vicinity of certain industries. Ifpresent, they can cause serious problems to annualbluegrass, especially hydrogen fluoride. Kentuckybluegrass is more tolerant (3).

EDAPHIC ADAPTATION

Physical Soil PropertiesAnnual bluegrass has long been recognized as a

grass which is quite capable of growing on com-pacted soil sites (l0, 11, 29, 58 and 100). In fact, it isconsidered an asset on heavily-trafficked, compactedsoils where it is often the only grass which persists (44and 55). But annual bluegrass has been described asshort rooted grass (39, 49 and 81). Its susceptibility tomoisture stress (l0) and nutrient deficiencies (29) tendto support the short-rooting theory.

As early as 1937, however, Sprague and Burtonstudied root growth of annual bluegrass (l00). Theyobserved that when annual bluegrass, Kentucky blue-grass, and colonial bentgrass were grown in uncom-pacted soils, there was essentially no difference inrooting among these three grasses in the top 7.6 cm(3in) or at the 12.7cm (5in) depth.

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This was substantiated by Wilkinson and Duff (115)comparing annual bluegrass, Kentucky bluegrass, andPenncross creeping bentgrass rooting. They found nodifferences in rooting among the grasses. Nor wasthere any difference in rooting of annual bluegrass ina sandy loam soil compacted to densities of 1.1, 1.25,and 1.4 grams oven dry soil/cc. Field observations,however, have revealed reduced rooting under com-pacted soil conditions (12, 100 and 117).

Sprague and Burton (l00) reported that annualbluegrass was better able to tolerate poor soil aerationduring cooler seasons, resulting in its encroachmentinto desirable turfs. Youngner (11 7) indicated that an-nual bluegrass can survive low soil oxygen levels, andthus is more competitive than other grasses undercompacted conditions.

Cultivation has been suggested as a practice toeither encourage or discourage annual bluegrass. Con-ditions at the time of cultivation have a marked effecton the competition between annual bluegrass andother species in polystands (101). Youngner (118, 119and 120) has suggested that a regular coring programduring the spring and fall is essential to growing an-nual bluegrass on compacted soils under Californiaconditions.

Any cultivation practice which exposes the soil un-der environmental conditions that favor annual blue-grass seed germination will likely result in increasedencroachment. Morgan et al (86) found reduced an-nual bluegrass on a compacted green which had beenintensively hand-cored and over-seeded with Seasidecreeping bentgrass. There was an increase in oxygendiffusion reading (a measure of available soil oxygen)and water infiltration rates after this intensive treat-ment.

Annual bluegrass responds to high soil moistureconditions. It is commonly found on moist sites whereit competes favorably with both cool and warm sea-son turfgrasses (l0, 46, 55, 99, 100, 95 and 117).However, it does not tolerate waterlogged conditionsand submergence for any period of time (9, 99 and100). On the other hand, annual bluegrass is quitesusceptible to water stress and wilting (l0 and 29).

Frequent irrigations not only make soils more sus-ceptible to compaction, but also provide the moist en-vironment that is conducive to annual bluegrass en-croachment. In an irrigation study on an annualbluegrass-bermudagrass polystand, Youngner (117)found that annual bluegrass persisted during the sum-mer when irrigated with 1.3cm (1/2 in) of water every3 to 4 days. The annual bluegrass did not survive theheat and water stress conditions when 1.9 cm (% in)of water was applied every 10 days while the bermu-dagrass grew well.

Sprague and Evaul (99) found that annual bluegrassgrew best on a fine-textured soil held at 50-60 % ofthe soil water holding capacity and only fair to poorat higher and lower moisture levels. Maintaining thesoil moisture at 30 % of the water holding capacityresulted in very little annual bluegrass in the poly-stand. Bea rd (10) pointed out that annual bluegrass isbest adapted to moist, fine-textured soils, but will per-sist on coarser-textured soils if irrigated frequently.

Adequate drainage is suggested as being necessaryfor maintaining annual bluegrass (10). Drainage isalso important in keeping the "desired" species whenarsenicals are being used to control annual bluegrass(22). The arsenate can be reduced to a more toxicform under high soil moisture conditions which canresult in serious injury to the desired turfgrasses.

Chemical Soil PropertiesSoil pH is an important factor in retaining annual

bluegrass in turfs. Most authors recommend pH levelsbetween 6.0 and 7.0 for favorable annual bluegrassgrowth (12, 85 and 88). However, Roberts et al (95)suggested that annual bluegrass is not likely to becontrolled by reducing the soil pH below optimumlevels because other turfgrasses do not competefavorably on acid soils either.

Several studies have shown that annual bluegrassgrows better at a soil pH of 6.5 than at 5.0 or 5.5(22, 74 and 100). Carrow (22) observed this responseon four different mineral soils ranging in texture froma loamy sand to a silty clay loam, as well as on apeat soil. Juska and Hanson (74) reported bettergrowth of annual bluegrass and more seedhead for-mation at pH 6.5 than at 4.5 on a loamy sand, butthere was no effect of pH when grown on a silt loamsoil. They also found that annual bluegrass grew bet-ter on the acid (pH 4.5) silt loam soil than did Ken-tucky bluegrass. Ferguson (39) suggested that low soilpH's result in reduced seed germination of annualbluegrass. He found less annual bluegrass on plotsreceiving acid- forming fertilizers.

When using calcium arsenate for annual bluegrasscontrol, Carrow (22) observed that raising the soil pHto 6.5 or 7.5 reduced the ability of calcium arsenateto control annual bluegrass. The arsenate is lessavailable to the plant at higher pH levels, thus reduc-ing its toxicity. To encourage the growth of annualbluegrass in turfs which have been treated with cal-cium arsenate in the past, one can reduce the arsenatetoxicity by liming to raise the soil pH or by applyingphosphorus (22, 28, 41 and 73).

There is little data published on the effects of solu-ble salts on annual bluegrass. Beard (10) ranked thesalt tolerance of annual bluegrass as low compared to

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other turfgrasses. Youngner (118) reported that an-nual bluegrass is highly susceptible to salt injury.Salts tend to accumulate near the soil surface duringhot weather in dry climates and can be a result fromregular, light syringing. Occasional deep irrigation isneeded to leach salts out of the turfgrass root zoneunder these conditions.

PESTS

This section on pests is based on the experiences ofthe authors and that of others in their respectivefields. Because annual bluegrass has been considereda weed little in-depth research has been conducted onits pest problems. Most of the information available isfrom observation and little data is published fromscientific experiments conducted under controlled con-ditions.

It is hoped that questions raised in this sectionabout certain pests will stimulate research to findsome needed answers. For current suggestions to con-trol the pests discussed herein, consult you Coopera-tive Extension Service representative or other quali-fied turf specia list.

DISEASES

The major diseases on annual bluegrass are an-thracnose, caused by Colletotrichum graminicola Ces.Wils.; brown patch, caused by Rhizoctonia solaniKuehn; dollar spot, caused by Sclerotinia homeocarpaF. T. Bennett; Fusarium patch, caused by Fusariumnivale (Fr.) Ces.; Pythium blight, caused by Pythiumspp.; red thread, caused by Corticium fuciforme (McAlp.) Wake; Typhula blight, caused by Typhula spp.Of these diseases, anthracnose appears to be the mostimportant and can be a limiting factor in successfullygrowing annual bluegrass during periods of hot, hu-mid wea ther.

Other diseases which are reported to occur on an-nual bluegrass are leaf mold, caused by Alternariaspp.; stem rust, caused by Puccinia graminis Pers.;leaf r~st, caused by Puccinia poae-sudeticae (West.);stripe smut, caused by Ustilago striiformis (West)Niessl. f. spp. poae-annuae; Ophiobolus patch, causedby Ophiobolus graminis Sacc.; and melting out,caused by Helminthosporium vagans Drechler. Table2 lists the important diseases which attack annualbluegrass and their cultural controls.

If melting out does occur on annual bluegrass, it isof minor importance in terms of turfgrass injury. Al-though fungicides are applied in the spring for thecontrol of melting out on golf course turfs, Vargas(112) has not observed the problem even in fairways

Table 2. Symptoms and cultural controls for important diseases of annual bluegrass.

CASUAL ORGANISM

ANTHRACNOSE(Colletotric humgraminicola)

BROWN PATCHrHhizoctoniasolani)

DOLLAR SPOT(Sc/Protill iahompoca rpa)

FUSARIUM PATCHPink Snow lvlold(Fusarium nivalp)

PYTHIUM BLIGHT(?ythium spp.)

RED THREAD(Corticiumfuciforme)

TYPHULA BLIGHTGray Snow Mold(Typhula spp.)

DISEASE SYMPTOMS

Irregular shaped patches varying in size from 6 inches up to severalfcet, eventually covcring entire fairways or grcens. Spots firstappear yellow, turning quickly to bronze during hot humidweather.

Large brown circlcs, 0.5 to 4 feet in diameter. Outer edgesometimes having a dark purple band of mycelium.

Tiny spots, 0.5 to 3 inches in diameter; straw to bleached colored,sometimes coalescing to form larger spots. The brown bandinglesion found on other grasses is not present on annual bluegrass.

Spots are circular, reddish brown, usually 1 inch to 2 feet indiameter when occurring without snow cover. Under snow coverthe spots are bleached tan to straw colored with red to pinkishmargins.

Water soaked spots, latcr fading to light brown, 1-6 inches indiameter, which may rapidly coalescc to form larger irregularspots. Spots sometimes have purple or white colored mycclia of thefungus present around the perimeter.

Light tan to pinkish spots, ranging in size from 2-6 inches. Redcolored stroma (threadlike structures) of the fungus usually presentin spots.

Circula r 0.5 to 2 feet spots, gray in color immediately after snowfall when mycelium of the fungus is present; later fading to a strawcolor as they dry. Reddish brown to dark brown sclerotia areusually present in spot. Occurs only under snow cover.

CULTURAL CONTROL

Moderate nitrogen fertilization willreduce the severity especially duringcool weather.

(I) Avoid high nitrogen levels.(2) Increase air circulation.

(I) Increase the nitrogen fertilitylevel.

(2) Remove dew and guttation waterin early morning.

Avoid fa II fertilizations that result insucculent turf prior to the first snow.

(1) Improve soil drainage.(2) Increase air cirulation.

Increase nitrogen level.

Avoid fall fertilization that results insucculent turf prior to snow fall.

where Kentucky bluegrass patches were severelythinned by disease. Jackson and Smith (68) also reportHelminthosporium as not being a problem on annualbluegrass in England. Helminthosporium is verydestructive on many susceptible Kentucky bluegrass,chewings fescue, and red fescue cultivars. This givesannual bluegrass a distinct advantage over the otherspecies because it competes well in the spring whenthe Helminthosporium susceptible cultivars are beingseverely thinned.

AnthracnoseAnthracnose is a disease that occurs on annual

bluegrass in both cool and warm weather. The diseaseturns annual bluegrass yellow in cool weather (Fig.11)3. The yellow, infected annual bluegrass plantsturn a bronze color at air temperatures above 29C(85F) and die if a fungicide treatment is not appliedwithin 48 hours.

Increased nitrogen fertilization may help reduce theseverity of anthracnose if it occurs during coolweather, but increasing the nitrogen level just prior to

3Fig. 11 is a color picture located on the inside back cover.

11

the advent of warm weather will increase the severity.Anthracnose can be easily recognized, with the aid ofa hand lens, by the black fruiting bodies (acervuli)which occur in rows in the interveinal areas of theleaf blades (see Fig. 12). These black fruiting bodiescontain spines called setae (97 and 112).

Fig. 12. Closeup of acervuli with setae of Colletotri-chum graminicola (anthracnose) growing in interveinalareas on annual bluegrass. (Photo-J. M. Vargas, Jr.)

Brown Patch and Pythium BlightBrown patch can be a severe problem on annual

bluegrass. It is a disease which occurs at temperaturesabout 29C (85F), along with a high atmospheric hu-midity and night temperatures remaining about 21C(70F). High nitrogen fertility levels preceding an in-fection can increase the severity of the disease.Pythium blight is a warm weather disease like brownpatch. Disease activity is favored by air temperaturesabout 32C (90F), high atmospheric humidity, andwater saturated soils. Improved air movement andsurface water drainage will help reduce the severityof both Pythium blight and brown patch.

Dollar SpotDollar spot is the most common disease of annual

bluegrass over a wide range of soil, environmental,and cultural conditions. It is a problem from latespring through early fall in the cool humid climaticregion. There are apparently two distinct strains ofthe fungus. One causes larger 5 to 7.6cm (2 to 3 in.)spots which occur in cooler weather of 16 to 24C(60- 75F), while another strain causes smaller 1.3 to2.5cm (0.5-1 in.) spots at higher temperatures of 24to 29C (75-85F). This means that dollar spot can bea problem for most of the growing season in someareas.

Fusarium PatchThis is a cool weather problem occurring at

temperatures below 16C (60F), and is also favored bywet weather. It will continue to grow under a snowcover where it is commonly known as pink snowmold. High nitrogen, liming, and higher pH's will in-crease disease severity on annual bluegrass (97).

Red ThreadRed thread is favored by cool temperatures of 13 to

24C (55-75F), and prolonged periods of light rain. Itis primarily a disease problem on slow growing turfsand is usually associated with low nitrogen fertilitylevels. It is one of the few diseases which can be con-trolled with a reasonable level of nitrogen fertiliza-tion. However, the possibility of increased snow moldor winter desiccation problems from late fall nitrogenapplications must also be taken into considerationwhen using nitrogen for red thread prevention.

Typhula BlightTyphula blight occurs only under a snow cover, or

its equivalent, such as leaves. It is a destructive dis-ease that can result in death of infected plants. Avoid-ing fall nitrogen fertility that will result in succulentgrowth prior to snow fall helps reduce the severity ofthis disease.

12

INSECTS

Ataenius spretulus grubs, turfgrass weevils, andgrubs from the Scarabaeide family are insect pestsspecifically associated with annual bluegrass. Otherinsect problems associated with annual bluegrass in-clude billbugs, chinch bugs, cutworms, and sod web-worms. Information concerning the suspected prob-lems was compiled from Beard (12), Madison (82),and App and Kerr (4).

Ataenius spretulus GrubAtaenius spretulus Hald. is a small, black beetle

whose larval (grub) stage can cause severe damage toannual bluegrass turf (90) (Fig. 13)4. It has been ob-served to be a problem in the northeast and midweston annual bluegrass, Kentucky bluegrass, and bent-grass. Officially, it does not have a common name,although many have called it a dung beetle.

Small grubs (Fig. 14)4 of the insect are responsiblefor the damage. Initial symptoms are the wilting oflarge, irregular shaped patches of turf. The beetle over-winters as an adult and lays eggs in the spring. Thelarvae emerge in late June and July at which time theycan cause severe damage to annual bluegrass, which isalready under high temperature stress, by feeding onthe roots. This results in wilting and eventual death.

Chinch BugChinch bugs (Blissus spp.) can be a problem on an-

nual bluegrass. Adult chinch bugs are 0.4 to 0.5cm(1/6 to 1/5 in.) long and black with white wingsfolded over the back. Eggs are laid in the annualbluegrass crown area. The nymphs grow from a redpinhead size with a white band across the back tobrownish, 0.5cm (1/5 in) long adults. They gothrough approximately five instar stages in six toeight weeks.

Chinch bugs prefer hot, dry weather and turfgrassdamage is most severe under these conditions. Injuryinitially appears as irregular, yellowish patches, 61 to81 cm (2-3 ft) in diameter, usually in sunny areas.These patches can coalesce and spread to involvelarger areas. The grass will eventually turn brownand die if the pest is not controlled.

If chinch bugs are suspected as a problem, they canbe diagnosed by removing both ends of a coffee canand firmly pushing it into the sod on the edge of theinfected area. The can should then be filled withwater and held in position for 5 to 10 minutes. Anychinch bugs present will float to the surface of thewater.

'Figs. 13 and 14 are color pictures located on the outside backcover.

GrubsGrubs are root feeding larvae and are represented

by many species of beetles belonging to the familyScarabaeide. The larvae are 2.5 to 3.8 em (1-1.5 in.)in length and white to pale yellow in color. Theyhave brown heads, six legs, and are usually found ina curled position. These larvae feed on the turfgrassroots. The sod can be easily lifted when severe infesta-tions occur and are easily seen upon lifting the sod.Other indications of grub activity include the pres-ence of moles, birds, and skunks which feed on thegrubs by tearing up the turf.

Sod WebwormSod webworms (Crambus spp.) are the larvae of

small whitish or grayish lawn moths that can be ob-served flying over turfgrass areas in the evening. Thelarvae feed on the turfgrass leaves and build them-selves silk lined tunnels or burrows just below the soilsurface. They are most active at night when theychew off grass blades near the soil surface. Silky webscovering the tunnel are sometimes evident early in themorning.

Turfgrass WeevilThe turfgrass weevil or Hyperodes weevil (Hyper-

odes spp.) has been identified as an important prob-lem of annual bluegrass in the northeastern UnitedStates (102). It was originally identified as a problemon turf in Connecticut (19). Tashiro (102) reports thatthe weevil feeds on annual bluegrass, clover, bent-grass, and fescue, but rarely on Kentucky bluegrass.

The only significant turfgrass damage has been ob-served on annual bluegrass. The major damage iscaused by larvae feeding. Initial symptoms involve ayellowing of individual, centrally located leaves of thegrass plant. Yellow spots less than 2.5cm (1 in.) indiameter appear on greens. Large areas will be dam-aged if the initial infection is not controlled. Damageis first evident during late May and June and is re-stricted to areas where annual bluegrass is maintainedat a cutting height of 0.5 in. or lower.

According to Tashiro (102) the life cycle consists ofthe female laying her eggs in the leaf sheath througha small hole she has chewed. After hatching, the lar-vae feed within the stem on the youngest, most tendertissue. The central leaf becomes yellow and may die.The stems are often hollowed out. The larvae alsofeed on the crowns and may eventually destroy theentire plant (Fig. IS).

Fig. 15. Closeup of a turfgrass weevil larva (left) andthe adult beetle (right), (Photo-H. Tashiro)

13

CutwormsCutworms are mainly a problem on annual blue-

grass greens. During the day the larvae live in theholes left by coring. At night they feed around thecoring holes cutting the grass off at the soil surface.The damage is unsightly and interferes with putting.

The cutworm larvae are fat and almost smooth,ranging in size from }I/2-2 in. (3.8-5.1 cm) long. Theyvary in color from grey to brown to black. They maypossess either spots or stripes. The cutworm moths arenight fliers and are brown or grey in color. They be-long to the family Noctuidae and lay their eggs on theplants. There can be up to 4 generations per season.

NEMATODES

Five species of nematodes have been associated withproblems in annual bluegrass. The most common arethe: I-root knot nematode, Meloidogyne arenaria(Neal) Chitwood; 2-stylet nematode (a stunt nema-tode), Tylenchorhynchus acutus Allen; and 3-lancenematode, Hoptolaimus tylenchiformis Daday (27).Vargas has also found Tylenchorhynchus dubius(Butschli) Filipjev. and Criconemoides spp. associatedwith problem annual bluegrass turfs. There are prob-ably many other pathogenic nematodes causing prob-lems in annual bluegrass turfs; but because of itsclassification as a weed, this problem has also beenoverlooked.

In general, root feeding nematodes cause symptomswhich are associated with poor quality turf. The turfoften looks as though it is lacking fertilizer and/orwater. The affected areas can appear light green toyellow in appearance or have the purplish color ofwilting turf which is caused by the damaged rootsystem. If nematodes are suspected, a soil sampleshould be sent to a qualified nematology laboratoryfor examination.

Controlling nematodes can be a difficult problem.Any control short of complete sterilization results inan initial decrease in the nematode population; whichin turn, results in a new flush of root growth thatallows the nematode population to build back upagain. This means a continual cycle of treatments toreduce population build-ups or to control populationsat low levels. However, such a program must be fol-lowed if the nematodes are causing loss of annualbluegrass turfs. Extreme caution should be takenwhen using nematicides because most of them arehighly toxic, both dermally and orally.

14

PROPAGATION

Seed ProductionThe propagation of annual bluegrass is primarily

by seed; however, studies with various biotypes of an-nual bluegrass have shown that vegetative propaga-tion by stolons may also be important in the spreadand survival of the plant (10 and 46). Renney (92) ob-served that a single plant of annual bluegrass growingin western British Columbia, Canada, produced morethan 360 seeds during a four-month period from Maythrough August. He estimated that, where annualbluegrass has been growing, the surface layer of soilmight contain 30 million annual bluegrass seeds peracre.

Koshy (78) reported that seed formation can pro-ceed following pollination, even when the panicles areremoved from the plant on the same day pollinationoccurs. He concluded that annual bluegrass has ahighly efficient sexual reproductive system that con-tributes greatly to its success as a weed, even underclose mowing.

Annual bluegrass is unique. It produces an abun-dance of seed stalks at all cutting heights (91). Seedformation occurs throughout the growing season butis most intense during mid-spring (100). Youngner(118) determined that temperatures within a range of10 to 27C (50-80F) had little effect on flowering.Whereas most plants require a specific photoperiodfor floral induction, annual bluegrass flowered nor-mally when subjected to 6, 9, 12, or 24 hours of lightper day (104).

Youngner (118) also reported that flower inductionwas not governed by day length. Sprague and Burton(100) determined that annual bluegrass growing incontinuous shade or under a 5-hour daily light ex-posure formed very few seedheads compared to plantsgrowing under longer photoperiods. They concludedthat adequate exposure to light is an important factorin the seed production of annual bluegrass. These re-sults reflect differential responses to photoperiod inthe case of floral induction and total daily light levelsreceived in the case of floral development.

Seed production has been reported to be affected byfertilization. Nitrogen increases vegetative growthwhile decreasing seedheads. Seedhead formation in-creases when phosphorus and potash are appliedalong with nitrogen. Lime applications reduced seed-head formation, probably because of greater vegeta-tive growth induced by nitrogen. However, Juska and

Hanson (74) found four times as many seedheads on'lnnual bluegrass grown in a sandy loam soil at pH6.5 compared to a pH of 4.5. No differences were ob-served when grown in a silt loam soil at the same twopH levels.

Another factor that has been associated with differ-ences in flowering is the morphological variabililtywithin annual bluegrass. Gibeault (46) found that an-nual biotypes (var. annua) flowered in 50 days com-pared to 81 days for the perennial biotypes (var. rep-tans). Even more important, the annual biotypes weremuch more prolific seed producers.

Seed GerminationGermination of annual bluegrass seed is believed to

occur primarily during cool, moist conditions in latesummer or early fall, with spring germination occur-ring in some areas (10, 56 and 101). More seed ger-mination was observed at a constant temperature of16C (60F) than at 10 or 21C (50 or 70F) (25). How-ever, Bogart (17) reported no differences in annualbluegrass seed germination at constant temperaturesof 4, 10, 16 or 21C (40, 50, 60 or 70F), but a verysubstantial decrease at 27 and 32C (80 and 90F). Thecontradictory results may be due to different biotypes,such as annual vs. perennial.

Engel (32) found tha t alternating temperatures of30C (86F) day and 20C (68F) night resulted in highergermination than constant temperatures of 20C (68F)and 30C (86F). Hovin (64) also found that alternatingtemperatures promoted annual bluegrass seed ger-mination. A study conducted at Michigan State Uni-versity in 1969 showed uniform seed germinationunder three alternating temperature regimes, butreduced germination at the lowest temperatures of13C (55F) day and 2C (35F) night (Table 3). Seedlinggrowth significantly increased with increasing tem-peratures and longer photoperiods. Thus, it wouldseem that annual bluegrass germination is most likelyto occur during relatively cool periods of the season.

Table 3. Effects of day/night temperature and photoperiodon seed germination and seedling growth of annualbluegrass.

Temperature Photoperiod Seed Seedling Height(day/night) Germination (after 2 I days)

(F) (hrs.) (%) (cm)55/35 8 63.5 a(aj 0.71 a(a)65/45 IO 83.5 b 1.38 b75/55 12 81.0 b I.72 c85/65 14 84.3 b 2.10 d

(a) Means in column with common letters are not significantly dif.ferent by the Duncan's Multiple Range Test at the 5% level.

15

Neidlinger (89) determined that the surface temper-atures of bare soil in mid-summer exceeded thoseunder turf by as much as 15C (28F), but the maxi-mum temperatures under a turf on sunny days werewithin those which permitted annual bluegrass ger-mination in the laboratory. He concluded that seedgermination could occur throughout the summer inturf, but that it would be unlikely on bare soil sincethe higher temperatures measured on bare soilparalleled laboratory test temperatures that inhibitedgermination.

Numerous researchers have reported that annualbluegrass seed germination is favored by light; how-ever, germination does occur in the absence of light(32, 64, 65, 89 and 92). Tutin (111) reported thatseed of var. reptans germinated as soon as conditionswere favorable while var. annua usually required athree month after-ripening period.

Cockerham and Whitworth (25) found that freshly-harvested seed in New Mexico failed to germinate inthe laboratory, but germination increased to 26% and47% after one and two months storage, respectively.Beard (10) concluded that dormancy of the annualtypes (var. annua) of annual bluegrass allowed theseed to remain in a viable condition in the soil forone or more years.

Other factors that have been reported as being im-portant in annual bluegrass seed germination includethe nutrient content of the external substrate and pH.Cockerham and Whitworth (25) observed increasedseed germination when using KN03 in the substrate.Ferguson (39) concluded that acid-forming fertilizers,such as ammonium sulfate, inhibited annual bluegrassgermination through a reduction in soil pH.

TURFGRASS COMMUNITY DYNAMICS

Beard (10) characterized annual bluegrass as an op-portunistic grass which frequently becomes estab-lished in turfs that have been weakened by errors inthe cultural program, or because of the lack of com-petition from non-aggressive bentgrass cultivars. Itcommonly invades turfgrass communities becausecompetition from existing turfgrasses has been re-duced below a critical level at a time when environ-mental conditions are favorable for annual bluegrass.

Reduction in competition may be due to the devel-opment of voids in the turf caused by diseases, insectinjury, traffic wear, divots, cultivation, or other stressconditions. The specific time during the growing sea-son when these voids occur determines the likelihoodof annual bluegrass invasion. Also, Sprague and Bur-

Fig. 17. Ecological scheme depicting the cuttingheight and soil moisture regimes as environmental fac-tors affecting the adaptation of Kentucky bluegrass(KB) and annual bluegrass (AB). (Photo-A. J. Turge-on).

MowingBogart and Beard (18) found the optimum cutting

height for annual bluegrass to be 2.5cm (1 in.) basedon studies comparing density and shoot weights ofpopulations clipped at 1.3, 2.5, 3.8, 5.1 and 6.4 cm(0.5, 1.0, 1.5, 2.0 and 2.5 in.), in monostands and inpolystands with Kentucky bluegrass.

Upon returning clippings to a Kentucky bluegrassturf mowed at 2.5 cm (l in.) Beard and Rieke foundannual bluegrass comprised nearly 30 % of the turfwhile there was only about 1% annual bluegrasswhen clippings were removed. When mowed at 5 cm(2 in.) there was essentially no annual bluegrass in theturf. Optimum cutting heights for Kentucky bluegrassare generally thought to be within a range of 3.8 to6.4 cm (l.5 to 2.5 in.).

IrrigationSprague and Evaul (99) found that fine textured

soils kept at 30 percent saturation had very little an-nual bluegrass, while higher soil moisture levels wereassociated with more annual bluegrass. Youngner(117) reported that high soil moisture levels main-tained by frequent, light irrigations favored the per-sistence of annual bluegrass in bermuda grass turf dur-ing the summer months in southern California.

Harper (56) and others observed that non-irrigatedturfs of Kentucky bluegrass were rapidly changed topredominantly annual bluegrass following frequent ir-rigation and closer mowing. The water requirementof creeping bentgrass is closer to annual bluegrassthan most other species based on field observations.However, basic data on comparative water use ratesand irrigation practices are not yet available.

ton (100) found wide differences in the amounts ofannual bluegrass in creeping bentgrass due to the rel-ative resistance of different cultivars to invasion.Similarly, Beard reports that annual bluegrass en-croachment into dormant bermudagrass is greaterwith Tifdwarf than Tifgreen under Texas conditions.This occurs because Tifdwarf discolors and entersdormancy earlier than Tifgreen; and at a more favor-able time for the seed germination and invasion of an-nual bluegrass .

Youngner (117) found that light vertical mowing ofbermudagrass turf in November resulted in a substan-tial increase in the annual bluegrass population thefollowing winter. He concluded that removing theheavy bermuda grass mat by vertical mowing encour-aged annual bluegrass seed germination under themoist, cool conditions that existed. Annual bluegrassinvasions were observed following severe incidencesof Fusarium blight in Kentucky bluegrass, and redleaf spot (Helminthosporium erythrospilum) in Toron-to creeping bentgrass.

Low temperature kill of crabgrass in autumn fol-lowed by favorable climatic conditions facilitated an-nual bluegrass invasion into a Kentucky bluegrassturf (Fig. 16)5. Annual bluegrass frequently invadesgolf course tees in bare areas resulting from divoting,and putting greens where tears in the turf occur fromlanding of golf balls and spiked shoes. Thus, mechan-ical and biological disruption of the turf should beavoided or quickly repaired to minimize the invasionof annual bluegrass.

Competition from desirable turfgrasses is reducedwhere prevailing environmental conditions differ sub-stantially from the "ecological niche" of the specificturfgrass. Fig. 17 illustrates the relative positions ofKentucky bluegrass (KB) and annual bluegrass (AB) inan ecological scheme depicting the cutting height andsoil moisture regimes as the principal environmentalfactors affecting adaptation of these species.

The center points of each set of concentric ringsrepresent the optimum conditions (ecological niches)for the respective grasses. Each concentric ring pro-ceeding outward from the center points representsdecreasing levels of adaptation. Overlapping of thetwo sets of concentric rings indicates that both speciesare adapted to the same set of conditions. However,one or the other may be preferred, depending on thespecific soil moisture level and cutting height selected.Thus, major shifts within the turfgrass communityaway from annual bluegrass and toward perennialturfgrasses can occur only when climatic, soil, andcultural conditions favor the desired perennial turf-grass.

SFig. 16 is a color picture located on the outside back cover.

16

high

CUTTINGHEIGHT

low

low

'------ -;: "-" .... '>. _'r- \

/ / - - - - r- .... ",.""- \ \ \

/ -' ,-~-,,>'- \_~-\-\/ / ,,/ -::.- /', "y-" \ \ \

I I / ," , < .. J( \ ~ - \" - - _\I I 1 1/, - rKB.\' \ / -r- \ \ \ I', I I I I I \) I \- - --l-

I I ~ \I " / I -t" I I I ....~\ \ /, I' - _ ,. , 1 / .f 1_ -r - -,. I\ \ .. 1,/ / , .... ,

\ \ -I. ;... _ 1_" 1 / 1 / 1 L _ /. "-\ , ....... I -, "I / //1 ...\ I\ "I ........-4 _ - r I / I / ' - -AB/ \'-'- r ....I I ,./ ".r ( I I( I II

.... '1 .....-1-, I" J( '- ,/,....\ ~ \ / , t- - I.........L. _ l.. _ 1,- \ /\ Y, - l' /

\ \ ,,'" / /

highMOISTUREREGIME---

(a) 4 pounds nitrogen was applied per 1000 square feet annuallyand divided into the appropriate number of applications.

Table 4. Time of application of ammonium nitrate effect onthe composition of a mixed annual bluegrass-Merion Kentucky bluegrass turf after 5 years oftreatments, at East Lansing, Michigan.

means of controlling annual bluegrass because of thepoor response of other turfgrasses to high soil acidity.

Juska and Hanson (74) studied the pH preference ofannual bluegrass in two soil types. They concludedthat annual bluegrass has the ability to grow betterthan Kentucky bluegrass at a low pH level in a heavysilt loam soil. The response of annual bluegrass to dif-ferences in pH depended upon soil texture.

FertilizationHigher fertility levels enhance annual bluegrass in-

vasion into Kentucky bluegrass turf (42 and 93).Engel (33) reported that cold-weather applications ofnitrogen cause an increase in the annual bluegrasscontent within a creeping bentgrass turf compared todistribution of the applications uniformly over the en-tire growing season. Rieke and Bay (93) found that us-ing treatments which apply more nitrogen during thespring encouraged annual bluegrass encroachment ina Merion Kentucky bluegrass turf (Table 4).

%8971888178635656

Annual Bluegrass in Turf

AprilApril. AugustApril, May, AugustFebruary, May, AugustMay, JulyApril, August, SeptemberMay, August, NovemberAugust

Date(s) of Application (a)

There is little information reported on the influenceof fertilizer carriers on annual bluegrass. But the con-tinued use of activated sewage sludge on Merion Ken-tucky bluegrass and Pennlawn red fescue turfs hasresulted in increased invasion of annual bluegrasscompared to urea and ammonium nitrate treatments(93).

Some non-technical literature suggests the spring ni-trogen fertilizations should be delayed to avoid en-couraging annual bluegrass growth at the expense ofbentgrass and Kentucky bluegrass. Bogart (17) deter-mined that Penncross creeping bentgrass and Merion

Soil ReactionSoil fertility and pH substantially affect the growth

and quality of turfs. Differences in the adaptation andresponse of turfgrass species to various levels of nu-trients and pH can be exploited to shift the turfgrasscommunity toward or away from a particular compo-nent of the polystand. Sprague and Burton (l00)found that annual bluegrass did not exhibit greatertolerance to soil acidity than other turfgrasses. Theyalso concluded that reducing the soil pH through theuse of acid-forming fertilizers was not practical as a

Soil CompactionBeard (10) reported that annual bluegrass is well

adapted to compacted soil conditions, while bentgrasshas poor compaction tolerance and Kentucky blue-grass is intermediate. A frequent observation in bent-grass fairways is the longitudinal pattern of annualbluegrass invasion corresponding to the traffic patternand differential soil compaction resulting from mow-ing equipment.

Sprague and Evaul (99) compared the rooting ofthree grasses in a clay loam soil under compacted andnon-compacted conditions. They found that the totalroot weight of annual bluegrass was reduced by one-half to two-thirds from soil compaction. Root growthin the top 7.5 cm (3 in.) of the compacted soil was87 % of the total root growth for annual bluegrass,92 % for Kentucky bluegrass, and 88 % for colonialbentgrass. Below 13 cm (5 in.) the root growths of allthree grasses were also similar, averaging 6 percent ofthe total.

Wilkinson and Duff (115) found that the rootingability of annual bluegrass was comparable to creep-ing bentgrass and Kentucky bluegrass at three soilbulk densities. They concluded that the success of an-nual bluegrass in compacted soils could not be ex-plained by superior rooting ability, but was probablythe result of its continuous seed production and re-newal of growth during cool seasons.

Youngner (117) reported significantly denser standsof annual bluegrass in bermudagrass mowed at 1.3 to1.9 cm (0.5 to 0.75 in.) than when mowed at 7.6 cm(3 in.). Variability within the annual bluegrass speciesis evidenced from reported differences among bio-types in growth habit, shoot density, persistence, andsusceptibility to control with chemicals (64, 65, 117,46, 10, 105 and 106). It is conceivable that biotypesof annual bluegrass might respond differently to vari-ous cutting heights which, in turn, could influencetheir competitive ability.

The effect of mowing height on the competitive re-lationship between bentgrass and annual bluegrass isnot well documented.

17

Kentucky bluegrass actually initiated growth at 2.8C(5F) lower soil temperatures than did annual blue-grass.

However, Hawes (58) found that annual bluegrassmade two to three times as much growth as Penncrosscreeping bentgrass at a soil temperature of 7C (45F).Penncross grew more and had a competitive advan-tage over annual bluegrass within a soil temperaturerange of 13 and 29C (55 and 85F). Furthermore, an-nual bluegrass produced a more horizontal growth atlower temperatures of 7 and 13C (45 and 55F), al-lowing for more rapid lateral growth into bare areas.

Goss (52) reported an increase in annual bluegrassinvasion into a bentgrass putting green in westernWashington by applying 56 kg/ha sulfur (1.1 Ibs/1 000sq ft) compared to the untreated plot. When the an-nual sulfur rate was increased to 168 kglha (3.4 lbs/1000 sq ft) however, annual bluegrass decreased to nomore than was found in the untreated turf.

A CULTURAL PROGRAMFOR ANNUAL BLUEGRASS TURFS

Many irrigated, closely-mowed turfs-especiallythose on golf courses-are composed primarily of an-nual bluegrass. So, cultural programs need to beselected that are optimum for maintaining quality,persistent annual bluegrass turf appropriate for theparticular use. Unfortunately, detailed information ofthis type has not been available in past publications.

This publication proposes a cultural system for an-nual bluegrass. The outline presented is based primar-ily on experience and observations of the authors,with inputs from the USGA Green Section Agrono-mists. The cultural system is based on the best avail-able information, but lacks confirmation by researchunder representative field conditions.

A CULTURAL PROGRAMFOR ANNUAL BLUEGRASS GREENS

Mowing Height: 3/16 to 5!l6 inch (5 to 8mm)Mowing Frequency: DailyClipping Removal: YesBrushing: Daily during peak seedhead formation and

three to four times per week during periods oflighter seedhead development. Same effect can beaccomplished with a light vertical mowing, espe-cially for those having a triplex greensmower.

Fertilization-Nitrogen: Requires 0.5 to 0.7 poundsof actual nitrogen per 1,000 square feet per grow-ing month. Apply between 0.25 and 0.5 pound ofactual nitrogen per 1,000 square feet per applica-tion, spaced at 10 to 20 day intervals. Avoid ni-trogen fertilization in the summer when heat stresslimits growth.

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Fertilization-Phosphorus: Application rate should bebased on soil tests using a program that maintainsa moderately high level of soil phosphorus. Appli-cations are best made in the spring or the fall,preferably just after coring so that deeper soilpenetration can be achieved. Most commonly ap-plied in the form of a complete analysis fertilizer.

Fertilization- Potassium: Apply based on soil testswhere finer textured soils are involved; coarse tex-tured soils will probably require 4 to 5 pounds ac-tual K20 per 1,000 square feet per year. Split intofour to six applications over the growing season.Potassium sulfate (K2S04) is safer to use thanpotassium chloride (KCl) and provides some sulfuras well.

Fertilization-Iron: Apply 1 to 2 oz. of ferrous sul-fate per 1,000 square feet per growing month; usethe lower levels in the northeast. May need a 3 oz.rate in 3 gallons of water where chronic ironchlorosis occurs. Iron response will be moremarked when soil pH is above 7.5.

Fertilization-Other Nutrients: Apply only if visualdeficiency symptoms appear. This is quite infre-quent except in certain limited locations.

Soil Reaction: Maintain the soil reaction in the pHrange of 6.2 to 7.2. Apply lime as needed based onsoil test recommendations for turf. Dolomitic lime-stone is suggested as the liming material for acidsoils. A soil test will confirm any need for magne-sium in the dolomitic lime.

Irrigation: Maintain a constantly moist soil rootzone, usually through daily, light, early morningapplications. Syringe as needed to prevent wilt,with the timing based on "foot printing" symp-toms.

Vertical Mowing: Use to produce a very light comb-ing effect as needed up to once per week for vari-able growth and grain control. May be needed alittle more frequently during peak seedhead forma-tion periods in spring and fall.

Topdressing: Apply two to four times per year. Sug-gest a minimum of twice per year with a springapplication at 0.2 to 0.3 cubic yard per 1,000square feet and a late fall application at 0.3 to 0.5cubic yards per 1,000 square feet. Combine as afollowup to cultivation when possible and usehigher application rates. Top dressing as often asevery 3 to 4 weeks during the growing season maybe helpful except during the summer stress periods.

Cultivation: Utilize two to four times per year; usethe higher frequencies on intensely trafficked greenson fine textured soils. Suggest a minimum of twice,involving very early spring (as soon as the equip-ment can be taken on the green), and an early falltiming. Avoid heat stress period if possible.

Spiking: Weekly throughout the summer when thesoil temperature is above 70 F.

Weed Control: Control broadleafs as they appear.Suggest using mecoprop (MCPP). Avoid phenoxyherbicides-such as 2,4-D or silvex-because of po-tential phytotoxicity during heat stress periods.Hand weed goosegrass. Avoid organic arsenicalsand preemergence weedy grass herbicides becauseof potential phytotoxicity.

Disease Control: Use a preventive fungicide programin which several effective fungicides are alternated.Dollar spot and anthracnose are usually the mostsevere depending on the climatic region.

Insect Control: Apply the appropriate insecticide asthe insect problems appear. The Ataenius spretulusgrub and the turfgrass weevil are of particular con-cern. Avoid emulsifiable concentrate formulationsof insecticides.

Drainage: Adequate drainage is essential for healthyannual bluegrass. If drainage is poor, use surfaceand subsurface drainage techniques for improve-ment.

A CULTURAL PROGRAM FOR ANNUALBLUEGRASS FAIRWAYS AND SPORTS FIELDS

Mowing Height: 1/2 to % inch (1.3 to 1.9cm)Mowing Frequency: Three times a weekClipping Removal: NoFertilization-Nitrogen: Apply 0.25 to 0.5 pounds of

actual nitrogen per 1,000 square feet per growingmonth.

Fertilization-Phosphorus: Application rate should bebased on soil tests.

Fertilization-Potassium: Application rate should bebased on soil tests. Use at 50 to 70 % of the nitro-gen application rate depending on soil if soil testsare not available.

Fertilization-Iron: Iron is usually applied only whena visual iron deficiency appears.

Fertilization-Other Nutrients: Apply if a specificvisual deficiency symptom is diagnosed.

Liming: Maintain the pH above 6.0. Apply limestoneas indicated based on soil tests.

Irrigation: Maintain a moist but not wet soil throughlight, frequent irrigations at two to three day inter-vals, depending on stress conditions.

Vertical Mowing: Not usually practical.Topdressing: Not practiced.Cultivation: Core in the spring and fall as needed to

encourage new seedling growth and for cultivation.Weed Control: Applied as needed; usually in the

spring and/or fall; be sure to use minimal rates.Disease Control: Some utilize a low-cost preventive

program for dollar spot control, where it is a seri-

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ous problem. Others follow a rigorous and morecostly program.

Insect Control: Apply the appropriate insecticide asneeded when serious insect injury appears.

CONTROL OF ANNUAL BLUEGRASS

Cultural ControlProcedures for effectively controlling annual blue-

grass infestations in turf must be developed, taking in-to consideration the environmental adaptation andcultural requirements of the specific turfgrass speciesand cultivar(s) in use. A thorough search of availablescientific literature consistently revealed two factorsassociated with annual bluegrass occurrence in turf:(a) reduced competition from the permanent turf-grasses and (b) favorable conditions for annual blue-grass during at least a portion of the growing season.

Reduced turfgrass. competition is usually attributedto: close mowing, excessive irrigation, poor drainage,compacted soils, inteI1se traffic, improperly timed soilcultivation and vertical mowing, or use of non-adapted species or cultivars (10 and 117).

Improper fertilization practices are sometimes asso-ciated with annual bluegrass invasion. In Illinois,high spring applications of nitrogen fertilizer (2 lbNil 000 sq ft in April and again in May) were foundto result in severe Fusarium blight incidence on Ken-tucky bluegrass in August (l08). The diseased turfswere subsequently invaded by annual bluegrass, whileturfs that had received a more moderate rate of ni-trogen fertilizer in spring (lib N/ 1000 sq ft or less inApril and May) remained weed-free.

A cultural program should be designed to optimizethe competitive ability of the specific turfgrass cul-tivar in use. This includes: (a) the timing, amount andform of plant nutrient application through fertiliza-tion; (b) the amount, frequency, and uniform distribu-tion of water provided through irrigation; (c) theheight, frequency, pattern and method of mowing; (d)the method, timing, and severity of cultivation; (e) theproper use of pesticides for controlling problemweeds, diseases, and insects; and (f) reasonable use ofthe turf.

Frequently, the turfgrass cultural program is se-lected to maintain a turf at a certain level of qualityrequired for a particular use. Golf course tees aremowed closely to provide firm footing, high shootdensity, and low shoot growth for play. Fertilizationand irrigation are performed frequently to maintainturfgrass density and to stimulate recovery from wearand divot damage. Fairways are also maintained un-der close mowing to provide adequate shoot densityfor a satisfactory ball lie. Irrigation is performedregularly to maintain shoot density, but fertilization

is conducted on a modest schedule to prevent ex-cessive shoot growth and, presumably, thatch.

Roughs receive a low intensity of culture and arefrequently the only areas on the golf course devoid ofannual bluegrass. The same turfgrass may be used forall three turfs; yet the culture of tees, fairways, androughs can differ widely in intensity. Selection of aspecific cultivar or blend of compatible cultivars bestadapted to each cultural intensity would be an impor-tant consideration in minimizing annual bluegrass in-vasion.

Different blends can be planted for the tees, fair-ways, and roughs to achieve the playability charact-eristics and growth rate desired for each type of turf.Furthermore, the cultural program would have to becarefully programmed based on a detailed knowledgeof the cultural requirements of the cultivars in use.

Creeping bentgrass is used for putting greens intemperate climates. Engel and Illnicki (37) indicatedthat the invasion of a bentgrass turf by annual blue-grass is less likely if irrigation is performed adequate-ly for the bentgrass, but less than required by annualbluegrass. Musser (88) cautioned that water should beapplied sparingly in early fall when annual bluegrassseed is germinating.

A suggested program includes provisions for ade-quate, properly timed soil aeration to encourage vig-orous growth of the desirable turf at the expense ofannual bluegrass; removal of clippings, where prac-tical, to prevent annual bluegrass seeds from fallinginto the turf; proper timing of fertilizer applicationsin late summer, before reestablishment of annualbluegrass; and using organic sources of nitrogen inthe fall to encourage bentgrass growth during coolweather.

Engel (32) suggested seeding bentgrass in late sum-mer, when 850 temperatures predominate, to helpbentgrass gain a headstart over annual bluegrass. Heconcluded that in spite of the problems with warmweather seedings associated with watering needs, latesummer seedings may still have an advantage overthose made in cool fall weather.

Bermudagrasses are used in warm climatic regionsfor many types of turf-including putting greens, tees,and fairways. Winter dormancy of this species allowsinvasion by annual bluegrass (Fig. 18)6 and otherweeds, especially if the turf is disturbed by cultivationor other causes (117). Engel and Ilnicki (37) empha-sized the importance of spring and summer fertiliza-tion to provide a dense stand of bermuda grass by latesummer prior to cool weather that favors annualbluegrass seed germination.

6Fig. 18 is a color picture located on the outside back cover.

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Youngner (117) reported that infrequent, deep ir-rigation which maintained modest to low soil mois-ture levels reduces the annual bluegrass content of abermudagrass turf during the summer months insouthern California. He also found that high mowingat 7.6 cm (3 in.) discouraged annual bluegrass inva-sion into bermudagrass compared to a 1.3 cm (0.5in.) mowing height.

Bermudagrass greens may be overseeded with cool-season turfgrasses in the fall to provide a green, grow-ing winter turf. The overseeded turfgrasses may per-sist for three to six months, depending upon locationand climatic conditions (96). The rate of establish-ment and persistence of the overseeded turfgrasses areimportant in preventing annual bluegrass invasion(113). The particular species, cultivar(s), and/orpolystands selected can also determine the competitivepotential and eventual extent of annual bluegrass in-vasion (10).

Chemical ControlAttempts at controlling annual bluegrass with

chemicals date back to the 1930's when lead arsenate,then used as an insecticide, was found to discourageannual bluegrass in turf (100). Since then, numerousherbicides varying considerably in their chemistryhave been reported as promising for annual bluegrasscontrol. Many have since been shown to have seriouslimitations, especially those with broad spectrumselectivity.

Inorganic Arsenicals.

Daniel (28) reported that calcium arsenate, leadarsenate, and sodium arsenite were effective in remov-ing annual bluegrass from Kentucky bluegrass andcolonial bentgrass turfs. He further indicated thatarsenic toxicity was inversely related to the soilphosphorus level. Engel and Aldrich (35) reportedsubstantial reductions in annual bluegrass in colonialbentgrass fairways from successive applications ofsodium arsenite in combination with 2,4-D. Turgeon(107) reported that calcium arsenate reduced thestand of annual bluegrass in closely-clipped MerionKentucky bluegrass turf and held it at approximately18 percent for one year.

Injury to bentgrass turf has been observed followingthe application of arsenic compounds (28 and 26).Engel et al (38) reported that the quality of bentgrassfairway turfs was often reduced to 50 percent of nor-mal from calcium arsenate. Also, late summer appli-cations were generally more damaging than mid-spring applications.

Turgeon et al (109) reported that repeated applica-tions of calcium arsenate to Kentucky bluegrass re-

suIted in thatch development, shallow rooting, higherwilting tendency, higher disease incidence, and re-duced water infiltration due to an alteration of soilphysical conditions due to the lack of earthworm ac-tivity and root growth.

Dickson et al (31) observed substantial differencesin turfgrass injury to 90 Kentucky bluegrass cultivarsfrom calcium arsenate applied at the rate of 4.8pounds a.i./I,OOO square feet in May and again inSeptember. Merion, Windsor, and Baron showed verylittle injury; Touchdown, Nugget, Pennstar, and Fylk-ing were moderately to severely injured. They cau-tioned that new Kentucky bluegrass cultivars shouldbe carefully tested for tolerance to calcium arsenatebefore embarking on an application program for an-nual bluegrass control. A similar situation may alsoexist with other species and herbicides. More informa-tion is needed in this area.

Freeborg (41) reported that annual bluegrass is lesssensitive to arsenic during short photoperiods com-pared to longer photoperiods. However, no change inresponse was observed under varying light intensities.He observed that higher temperatures resulted in anincrease in the rate at which arsenic fixation occurredin the soil. However, the sensitivity of annual blue-grass to arsenic also increased with increasing tem-perature.

Carrow et al (23) reported no effect of arsenic ap-plied at rates as high as 800 pounds As/acre on thegermination of annual bluegrass seed after incubationof arsenic with soil. Seed germination was inhibitedat 400 pounds per acre without incubation.

Freeborg (41) concluded that the arsenic must beconcentrated in the surface inch of soil to be toxic toannual bluegrass. Presumably, this is due to the fixa-tion of arsenic that occurs when it is mixed with thesoil medium. He determined that less arsenic is re-tained by organic sand than by silt loam, silty clayloam, or muck soils. Therefore, more arsenic wouldbe required to obtain equivalent amounts of extract-able arsenic and, thus, control of annual bluegrass insoils with higher clay and silt contents.

Soil moisture level and pH were also found to affectthe amount of extractable arsenic. Carrow (22) deter-mined that increasing the pH reduced the arsenic ac-tivity in soils. He also found that the amount of ex-tractable arsenic from treated soils was highest whenthe soil moisture was maintained at field capacitycompared to 85 % and 70 % of field capacity.

Musser (88) recommended eradication of annualbluegrass in late August with sodium arsenite appliedat 40 pounds per acre in 50 to 100 gallons of water.His subsequent renovation procedure called for: fourto six passes with a core cultivator to prepare the

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seedbed; application of lime and fertilizer as needed;pulverize and work cores into the holes; allow annualbluegrass germination to occur; apply sodium arseniteat 25 pounds per acre; and drag, seed, and roll thearea.

These rates are quite high. A 5 pound per acresodium arsenite rate usually kills annual bluegrass.Currently, paraquat is used more commonly thansodium arsenite for renovating annual bluegrass in-fested turfs. Regardless of the chemical used, suc-cessful renovation must also include correction of thebasic cause of turfgrass deterioration that led to theannual bluegrass invasion.

Sodium arsenite has been applied to dormant ber-mudagrass for control of annual bluegrass (116 and60). Paraquat is more commonly utilized now. Greatcare must be exercised to ensure that the warm-seasonturfgrass is completely dormant if injury is to beavoided.

Postemergence Herbicides.

Goetze (47) found that fall applications of neburongave excellent control of annual bluegrass with nosustained injury to Kentucky bluegrass. Mruk andDeFrance (87) reported fair to moderate control inathletic field turf with DSMA, chloropropham, andneburon. In tests by DeFrance and Kolett (30) severalcopper compounds showed promise for controllingannual bluegrass without objectionable injury tocreeping bentgrass.

Fluorophenoxyacetic acids were reported to inducesterility in annual bluegrass for four to six weeks.Maleic hydrazide (I pound per acre) reduced thenumber of annual bluegrass seedheads, but also seri-ously reduced the bentgrass content in polystands andallowed a substantial increase in white clover (35).

Goss and Zook (51) studied the effects of maleichydrazide plus chlorflurenol on annual bluegrass in-fested turfs in Washington. They reported substantialinhibition of seedhead formation with some tempor-ary discoloration of Merion Kentucky bluegrass andbentgrass. Other effects included: reduction of themowing requirement; control of some broadleafweeds; reduction of annual bluegrass stands withsome increase in the density of perennial turfgrasses;and reduced viability in annual bluegrass seed. Youngseedlings of annual bluegrass were reported killed byfall applications. The authors recommended overseed-ing with desirable turfgrasses in conjunction withautumn applications of maleic hydrazide + chlor-flurenol.

Long (79) found that where seedhead suppressionoccurred following treatment with maleic hydrazideand chlorflurenol, annual bluegrass seeds in the soil

were significantly lower in germination compared toseeds from untreated plots. However, even with themost effective chemical treatment there were stillmore than 30,000 viable seeds per square meter inthe surface 1 inch (2.5 em) of soil. He concluded thata control program based on seedhead suppressionalone would not be successful.

Engel and Aldrich (35) reported substantial reduc-tions of annual bluegrass in colonial bentgrass fair-ways following several applications of endothall inthe spring at 0.5 pounds per acre. Cockerham andWhitworth (24) reported selective injury to annualbluegrass in common bermuda grass turf at 4 to 6pounds per acre, but recovery was rapid, necessitatingrepeated treatments.

Turgeon et al (105) reported a substantial reductionof annual bluegrass in Merion Kentucky bluegrass fol-lowing a single application in September at both 2and 4 pounds per acre. However, the best control wasobtained with three I-pound-per-acre applications attwo-week intervals. Endothall caused temporarybrowning of the turf, but the Kentucky bluegrass re-covered selectively after three to four weeks. Granularformulations of endothall provided superior selectivity~)Ver folia r sprays in greenhouse studies; but fieldresults were variable.

Morphologically differing biotypes of annual blue-grass responded differently to endothall treatments. Aroot treatment with a 50 ppm endothall solution wasadequate to kill an upright-growing, annual biotype;twice that concentration only stunted a prostrate-growing, perennial biotype (Fig. 19). The selectivityof endothall in turfs was attributed to differences in

Fig. 19. Comparison of the differential effect of a 50ppm endothall solution applied to a root zone of an-nual and perennial biotypes of annual bluegrass.Herbicide application was made to the plants on theright side in each case. (Photo-A. J. Turgeon)

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absorption and action of the herbicide in root appli-cations, while morphological differences among turf-grass species, spray retention, and action contributedto selectivity following foliar applications (106).

Where endothal1 was applied to closely clippedKentucky bluegrass infested with annual bluegrass,Turgeon (l07) found that annual bluegrass quicklyreinfested the plots after each treatment. He con-cluded that it could not be controlled by strictlypostemergence herbicides where climatic and culturalconditions were so favorable to annual bluegrass.

Horn et al (61) reported the successful use of pron-amide for selectively controlling annual bluegrass inbermudagrass turf. They determined tha t a waitingperiod of at least 60 days was necessary to allow suf-ficient time for breakdown of the herbicide betweenapplying of pronamide and overseeding for wintergreens. The authors also found that pronamide wasvery useful in eliminating volunteer ryegrass andother cool-season grasses after the bermudagrass in-itiated growth in spring.

More recently, Meyers and McCarthy (84) foundthat applying activated charcoal a