sampling for scn, 28 - the bulletinbulletin.ipm.illinois.edu/pastpest/articles/pdf/9903.pdf · tips...

Tips for the World Wide Web Version of the Bulletin

As I have mentioned in previous issues, we will introduce new aspects andmake changes to the Pest Management & Crop Development Bulletin web siteall season long. You may have noticed that in the article “Corn Herbicide Pre-mixes” in issue no. 2 (April 2, 1999) of this Bulletin, Aaron Hager and MarshalMcGlamery referred to Table 5 in the text, but the table was not readily appar-ent. However, if you clicked on the underlined Table 5 in the text, the table ap-peared on the screen. “Pop-up tables” and “pop-up photos” will appear when-ever they are too large to fit within the regular format of the web site. To closethe pop-up window, simply click on “File” and then “Close,” or click on the“X” in the upper right-hand corner of the window; either action closes the win-dow that contains the table or photo and takes you back to the text. In the nearfuture, we intend to make it easier for you to close pop-up windows that containtables or photos.—Kevin Steffey

Corn Insect Pests: A Diagnostic Guide

In 1998 I worked with entomologists and editors at the University of Missourito develop a publication entitled Corn Insect Pests: A Diagnostic Guide (publi-cation number C1358). The printed version of the publication is available for$8.00 (plus shipping) from ACES Information Technology and CommunicationServices, University of Illinois, 1917 South Wright Street, Champaign, IL61820, telephone (800)345-6087; VISA and MasterCard accepted. The 48-pagemanual guides you through diagnostic steps to determine what insect pest mightbe causing problems at several corn growth stages. The manual is filled withcolor photographs of the insects and the injury they cause, and diagnostic tipshelp focus attention on certain characteristics.

Corn Insect Pests: A Diagnostic Guide also can be found on our IPM web siteat http://www.aces.uiuc.edu/ipm/field/corn/cip.pdf. Take a look at it and seewhat you think. Try the “zoom-in” feature if you want to see some close-ups ofsome of the insects that look so small in the field.—Kevin Steffey

Illinois Agricultural Pest Management Handbook

Many authors who write articles for the Bulletin include tables that list pesti-cides suggested for control of specific pests. We will continue to provide thesetables in the printed version of the Bulletin, but you can view similar tables andmore by visiting the Illinois Agricultural Pest Management Handbook on theweb at http://www.ag.uiuc.edu/~vista/abstracts/aIAPM.html. The entire hand-book can be viewed, and you can find the specific information you seek byscrolling through the table of contents. All 22 chapters of the handbook, in-cluding suggestions for management of insects, weeds, and plant diseases infield crops, can be viewed in full. Some chapters focus on rodent control, con-trol of insects in stored grain, and insect pest management for livestock andlivestock buildings, and other chapters include specific information about tox-icities, formulations, environmental hazards, and other properties of pesticides.The printed version of the handbook (publication number IAPM-99) is availablefor $20 (plus shipping) from ACES Information Technology and Communica-tion Services (address and telephone number provided previously); VISA andMasterCard accepted.—Kevin Steffey

FOR IMMEDIATE RELEASENo. 3 / April 9, 1999

Executive editor: Kevin Steffey,Extension Entomologist

Web subscriptions available:http://www.ag.uiuc.edu/cespubs/pest/For subscription information, phone

217.244.5166, or [email protected]

In This Issue

q WPS Compliance Resources, 22

q Black Cutworm Watch Begins, 22

q Additional Info About WhiteGrubs, 23

q 2(ee) Registrations: Pounce, 23

q Alfalfa Weevil Activity Is UnderWay, 24

q Soybean Herbicide Premixes, 25

q Waterhemp in 1999, 25

q Spring Has Sprung, Fall Has Fell,Weeds Are Here as Usual, 28

q Sampling for SCN, 28

q Managing Soybean Cyst Nema-tode, 29

q Recognizing Corn NematodeProblems , 30

P e s t M a n a g e m e n t & C r o p D e v e l o p m e n t B u l l e t i n • N o . 3 / A p r i l 9 , 1 9 9 9

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WPS Compliance Resources

Are you looking for concise informationabout the Worker Protection Standardprovisions? Are you not sure how it allapplies to you, or how to proceed if itdoes? Consider accessing the Universityof Illinois Pesticide Safety Education website (http://www.aces.uiuc.edu/~pse; se-lect “Other Resources”). At this site, youcan read and print the following informa-tional publications:

q “The WPS: A Quick Guide to theRule” (new trifold introductory bro-chure)

q “The Worker Protection Standard inIllinois” (new 19-page summary ofEPA’s “How to Comply Manual”)

q “The WPS Resource Guide for Illi-nois Agricultural Employers” (re-cently revised)

If you do not have access to the Internet,stop by your local University of IllinoisExtension office and ask for printed cop-ies of these materials. You may have topay a small fee for printing the docu-ment.—Bruce Paulsrud

INSECTS

The Black Cutworm Watch Begins

Among the soil-inhabiting insects thatcause headaches for corn growers, blackcutworms probably are the most feared.When black cutworm larvae occur inlarge numbers, the damage they cause tocornfields can be devastating. Manygrowers, particularly growers in southerncounties, protect their fields with applica-tions of insecticides intended to preventblack cutworm injury. However, we typi-cally recommend the wait-and-see ap-proach before recommending actionagainst black cutworms. Because blackcutworms do not overwinter in Illinois,we never know from year to year whethertheir densities will be large enough to

result in economic damage. Therefore, westrongly encourage diligent scouting ofcornfields when the seedlings emerge, andapplication of insecticides only when 3percent or more of the seedlings are cutbelow ground. Nevertheless, preventivetreatments may be appropriate in no-till orreduced-tillage systems where vegetationis plentiful during the adults’ egg-layingperiod (more on this later). The insecti-cides listed in Table 1 are preventivetreatments that can be considered in suchsituations.

Are there ways to anticipate the occur-rence of black cutworms? Because of theunpredictability of infestations of blackcutworms, a plan of scouting for blackcutworms and applying a rescue treatment(postemergence) only when necessary cansave many growers money. If people areaware of cutworm activity in an area, theycan prepare themselves for the potentialappearance of the pest. In the past, wesupervised a network of black cutwormpheromone traps to monitor flights ofadults in the spring as they flew into Illi-nois from southern states. However, be-cause of diminished resources, we havenot been able to maintain this network.Therefore, we rely on reports from peoplewho have placed pheromone traps in dif-ferent areas of the state. If you are check-ing one or more of these traps for blackcutworm adults, we would be grateful toreceive the information so we can pass iton to others.

We already have received some reports ofcaptures of male black cutworm moths in

pheromone traps. Carlyle Mueller,Monroe County, began checking for blackcutworm moths on March 17 and hasfound as many as four adult males on onedate (March 17). He found one or twomoths per night on six other dates throughApril 2. Doug Gucker at the Piatt CountyExtension Unit and David Feltes, Exten-sion Educator/IPM at the Quad CitiesExtension Center, both captured one blackcutworm moth on April 2. Jim Morrison,Extension Educator/Crop Systems at theRockford Extension Center, captured twomoths in one trap and three moths in an-other on April 4. Mike Roegge, ExtensionUnit Educator/Crop Systems at the Ad-ams/Brown Extension Unit, captured ninemoths during the weekend of March 27. Ifhe captured these moths in a 1- or 2-dayperiod, Mike’s capture qualifies as an“intense capture.” After an intense captureof black cutworm moths, we can predictwhen black cutworm larvae have devel-oped to fourth instars with the ability tocut plants (accumulation of 300 heat unitsabove a base temperature of 50˚F). Whenwe receive more information about cap-tures of black cutworm adults in phero-mone traps from different areas of Illinois,we will provide heat-unit accumulationsin these areas.

If you are examining pheromone traps forblack cutworms, you may encounter morethan one species of moth. The synthesizedsexual pheromone used with the traps issupposed to attract only black cutwormmales. However, other moths occasionallyaccidentally fly into the traps and get

Table 1. Insecticides suggested for prevention of cutworm injury to corn.Insecticide Amount of product per acre Timing and placementAmbush 2E* 6.4 to 12.8 oz PreemergenceAsana XL* 5.8 to 9.6 oz PreemergenceAztec 2.1G* 6.7 oz per 1,000 ft of row Band or furrow at plantingForce 3G* 3 to 5 oz per 1,000 ft of row Band or furrow at plantingFortress 5G*(SmartBox only)

3 oz per 1,000 ft of row Band at planting

Lorsban 4E 1 to 2 pt PreemergenceLorsban 4E 2 to 4 pt Broadcast, preplant incorporatedLorsban 15G 8 oz per 1,000 ft of row Band at plantingPounce 1.5G* 8 to 16 oz per 1,000 ft of row Band at plantingPounce 3.2EC* 4 to 8 oz PreemergenceWarrior T or 1E* 1.92 to 3.2 oz Preemergence* Use restricted to certified applicators only.


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stuck on the sticky substance. Therefore,it is important that you are able to identifyblack cutworm moths. The adult moth hasa wingspan of 1 1/8 – 1 5/8 inches. Thebasal two-thirds of the forewing is dark,and the outer third is much paler. One ofthe easiest characteristics to see is thedagger-shaped marking at the outer edgeof a kidney-shaped spot toward the mid-dle of the forewing (Figure 1). Moths thatlack this characteristic are not blackcutworms.

So what is the life cycle of black cutwormsin Illinois, and what types of fields aremost at risk? As indicated previously, theblack cutworm does not overwinter in theMidwest, except occasionally in the Mis-sissippi delta region of southeastern Mis-souri. Adults migrate from the Gulf statesand arrive in the Corn Belt within 2 to 4nights. This annual immigration is heavi-est during April and May. Females de-posit eggs singly or in groups (as many as30) on pasture and fencerow grasses andon low, densely growing weeds and debrisin fields that have not been tilled. Damp,low-lying areas in fields that have notbeen tilled are particularly attractive foroviposition. Females firmly attach eggs todensely growing plants such as curleddock, yellow rocket, velvetleaf, and roughpigweed, or to fine-textured plant debrissuch as dead foxtail or soybean stems.Females rarely deposit eggs on livingsoybean or corn plants. Typically, ifweeds are destroyed early and corn isplanted relatively early, black cutwormsdo not pose much of a threat. However, ifplanting is delayed and cutworms have achance to develop on weeds before the

weeds are destroyed, the potential forcutworm damage increases.

Do black cutworms have any naturalenemies? The most important parasitoidsthat attack older black cutworm larvae arethe fly Bonnetia comta and the tiny waspMeteorus vulgaris. Predation by groundbeetle larvae and adults (Scarites sub-striatus, Pterostrichus chalcites, P. lu-cublandus, and Harpalus pennsylvanicus)also may reduce densities of black cut-worms. However, these natural enemiesoften do not keep densities of black cut-worm larvae below economic levels.

We will offer some more commentaryabout rescue treatments for cutworm con-trol in future issues of the Bulletin. Again,if you obtain any information about cap-tures of black cutworm adults in phero-mone traps, please pass it along.—KevinSteffey, Mike Gray

Some Additional Information AboutWhite Grubs

A couple of folks asked me this past weekabout what to do this year if they ob-served white grubs in their fields last year.It is probably a good idea to review thelife cycle of the true white grubs (Phyllo-phaga spp.).

True white grubs complete a single gen-eration in 3 years in northern areas,sometimes in 2 years in southern areas.Each female deposits 35 to 60 white eggsin individual cells 1 to 8 inches deep inthe soil. Small, C-shaped first instarsemerge 2 to 3 weeks after egg depositionand feed on organic matter. Larvae moltonce during their first summer. Grubsthen move to a depth below the soil frostline. Second instars migrate upward andbegin feeding on plant roots in the springof the second year. Larvae feed heavily onroots the entire second summer; thusdamage usually is greatest in the secondyear of the life cycle. Grubs molt to thethird instar by late fall and again descendin the soil. Larvae ascend in the spring ofthe third year and feed until mid- to latesummer. Crop stand reduction as a result

of feeding by true white grubs also canoccur early in the third summer, althoughdamage usually is not as extensive asduring the second year. In late July, grubsform earthen cells in which they pupate.During late August and early September,pupae transform to adults, which emergethe following spring.

Recent studies in the northern Corn Belthave shown that densities of Phyllophagaare larger in fields bordered by cotton-wood or willow trees. The adults feed oncottonwood and willow trees in the sur-rounding shelterbelts (windbreaks) atnight. At sunrise, they drop from the foli-age to the soil surface. Females fly fromthe trees and lay eggs in the soil, usuallyin those areas that are adjacent to theshelterbelts. Consequently, areas of fieldsnear shelterbelts usually suffer the great-est damage caused by the white grublarvae.

This information suggests that if youfound full-grown white grub larvae lastyear, the odds are they will not be presentat all this spring or, at most, for only abrief period of time. Also, if you observedwhite grubs in corn last year and the af-fected fields will be planted to soybeans,you won’t have to worry about injury tothe soybeans. Some soil sampling beforecorn is planted next year would beappropriate.—Kevin Steffey

2(ee) Registrations for Pounce

FMC Corporation has issued FIFRA sec-tion 2(ee) labels for Pounce 1.5G andPounce 3.2EC. These labels can be usedin all states where the crop and pest(s)exist and where 2(ee) recommendationsare recognized. Basically, a section 2(ee)registration allows use of a product tocontrol a pest in a manner not specified onthe federal label, as long as the product islabeled for that site (e.g., crop) and themaximum registered rate of application isnot exceeded. FMC has issued a 2(ee)label for Pounce 1.5G to control wire-worms, seedcorn maggots, and sodwebworms in field corn. The rate of ap-plication is 6.7 to 13.3 pounds of product

Figure 1. Black cutworm moth, showing thecharacteristic dagger-shaped mark on theforewing.


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per acre or 8 to 16 ounces of product per1,000 linear feet of row, applied at plant-ing directly into the seed furrow. Thehigher-labeled rate is recommended forheavy wireworm infestations. The 2(ee)label for Pounce 3.2EC is also for controlof wireworms, seedcorn maggots, and sodwebworms in field corn. The rate of ap-plication is 4 to 8 ounces of product peracre or 0.3 to 0.6 ounces per 1,000 linearfeet of row, applied at planting directlyinto the seed furrow. Again, the higherlabeled rate of application is recom-mended for heavy wireworm infestations.However, FMC personnel recommendthat a planter-box seed treatment be con-sidered as a first choice (I assume forwireworms and seedcorn maggots), andPounce 1.5G or Pounce 3.2EC should beconsidered by those growers who do notlike to use seed treatments.

Although 2(ee) labels are recognized inIllinois, we do not know whether Pounceis effective against the intended targetpests in the manner indicated on the la-bels; we have seen no efficacy data. Inother words, we urge caution before youdecide to go this route for control ofwireworms, seedcorn maggots, and sodwebworms. Alternatives for control ofthese pests exist, and the efficacy of someof the alternatives is known. We willsearch for efficacy data regarding theclaims on FMC’s 2(ee) labels and offerour insight accordingly.—Kevin Steffey,Mike Gray

The Data Indicate That AlfalfaWeevil Activity Is Under Way

Although we have received no reports yet,heat-unit accumulations indicate that al-falfa weevil larvae are probably active insome counties in southern Illinois. Figure2 shows accumulated heat units (above abase temperature of 48˚F) from January 1to April 4. Robert Scott with the IllinoisState Water Survey generated the datafrom the Illinois Climate Network. Anearly peak of third-stage larvae fromoverwintering eggs occurs after an accu-mulation of 325 heat units, so larvae

could be active anywhere south of a linefrom Calhoun County in western Illinoisto White County in eastern Illinois. As ofApril 4, scouting should have been underway anywhere south of a line from AdamsCounty in the west to Lawrence County inthe east. Projected warm temperaturesover the next several days will acceleratethe development of alfalfa weevils.

Again, we remind you to look first forsmall larvae feeding in the terminalleaves. The resulting pinhole-like feedinginjury, although not economic, is an earlyindication of the presence of alfalfa wee-vils. An insecticide may be warrantedwhen 25 to 50 percent of the tips are be-ing skeletonized and there are three or

more larvae per stem. If you decide toapply an insecticide, please read all pre-cautions carefully, and follow all direc-tions on the label. Insecticides suggestedfor control of alfalfa weevil larvae arepresented in Table 2.

To look for alfalfa weevil larvae, scout ina U-shaped pattern and pick 30 stems,spaced systematically along your sam-pling path. Select each stem randomly toavoid picking only those that have signsof injury. Snap the stem off at groundlevel and invert it into a bucket. After youhave gathered all 30 stems, you can de-termine the amount of injury and thenumbers of larvae at your leisure. Shakethe stems against the sides of the bucketto dislodge the larvae, and examine thestems for tip-feeding and defoliation. Af-ter you count the dislodged larvae, divideby 30 to obtain an average number oflarvae per stem.

We suggest one other consideration be-fore you decide to apply an insecticide. Inrecent years, natural enemies of alfalfaweevils have kept their populations incheck in some areas of the state. Althoughwe do not have supporting evidence, wesuspect that the parasitic wasps Bathy-plectes curculionis and B. anurus, as wellas the fungal disease organismZoophthora phytonomi, may be sup-pressing weevil populations. In some in-stances, insecticide applications could bevery disruptive to natural enemies, espe-cially the parasitic wasps. In the next is-sue of the Bulletin, we will provide moreinformation about these important bio-logical control agents.—Kevin Steffey

Figure 2. Actual heat-unit accumulations(base 48˚F) from January 1 through April4, 1999, for estimating development ofalfalfa weevils. (Map provided by RobertScott, Illinois State Water Survey.)

Table 2. Insecticides suggested for control of alfalfa weevil larvae.Insecticide Amount of product per acreAmbush 2E* 12.8 ozBaythroid 2* 1.6 to 2.8 ozFuradan 4F* 1/2 to 1 ptImidan 70-W 1 1/3 lbLorsban 4E 1 to 2 ptPenncap-M* 2 to 3 ptPounce 3.2Ec* 8 ozWarrior T or 1E* 2.56 to 3.84 oz* Use restricted to certified applicators only.


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WEEDS

Soybean Herbicide Premixes

Table 3 contains information about soy-bean herbicide premixes. This table isintended to be a reference guide only.Before using any of these herbicides, con-sult the respective product labels for ad-ditional information.—Aaron Hager,Marshal McGlamery

Waterhemp—What to Expect in1999

Someone once said the only certainties inlife are death and taxes. It seems reason-able to add “weeds” to this list of certain-ties. Although numerous weed speciespresent management problems each year,waterhemp has emerged as one of themost troublesome weed species that Illi-nois corn and soybean producers face.Several theories have been proposed toexplain why waterhemp has become oneof the dominant weed species in Illinoisagronomic production fields. Althoughthese theories help understand the “why,”producers are often struggling with the“how” when it comes to managing thisweed. In this and the following issue ofthe Bulletin, we’ll explore the biology ofwaterhemp and offer suggestions formanagement in both corn and soybeanproduction systems.

Waterhemp Biology

Waterhemp belongs to the botanical Ama-ranth family, which also includes theother pigweed species found in Illinois.The Latin or scientific name of each pig-weed contains the genus name Amaran-thus; each respective species name differ-entiates among the genus members.Historically, plant taxonomists have rec-ognized two distinct waterhemp species:tall (Amaranthus tuberculatus) and com-mon (Amaranthus rudis). Even though theliterature recognizes two waterhemp spe-cies, from a management standpoint thereis little reason to be able to differentiate

between these two species. We are notaware of any data that suggest that thesetwo species respond any differently toherbicides. Additionally, the only way toaccurately differentiate between tall andcommon waterhemp is to examine howthe thin membrane surrounding the seed(utricle) fractures when abraded. Unfortu-nately, the time of the season when theplants are at a developmental stage toallow this identification procedure is alsoclose to the time for harvestingoperations.

Tall and common waterhemp (referred tocollectively as waterhemp) are two ofnine pigweed species that can be found inIllinois. Prior to the rapid expansion ofwaterhemp, smooth pigweed (Amaranthushybridus) was probably the most preva-lent pigweed across much of Illinois.During early vegetative stages, smoothpigweed is nearly impossible to distin-guish from redroot pigweed (Amaranthusretroflexus), another commonly encoun-tered pigweed species. Palmer amaranth(Amaranthus palmeri) can be found in thesouthern quarter of Illinois. Like water-hemp, Palmer amaranth is a dioecious(separate male and female plants) speciesand, from personal observations, appearsto be moving northward in Illinois.Palmer amaranth may be the most aggres-sive pigweed species with respect togrowth rate and competitive ability. Pow-ell amaranth (Amaranthus powellii) isusually found in the northern portions ofIllinois, but it can also be found in centralregions of the state. Spiny amaranth(Amaranthus spinosus) is rapidly identifi-able by grabbing the stem with barehands. As the name accurately implies,sharp spines are present where leaves at-tach to the stem. Although not very com-mon in agronomic cropping systems,spiny amaranth can commonly be foundin pastures and around cattle feedlots. Thetwo other pigweeds, tumble (Amaranthusalbus) and prostrate (Amaranthus blitoi-des), are generally not considered to be astroublesome as other Amaranths.

Waterhemp plants are either male or fe-male (dioecious). Thus male plants pro-

duce only pollen, whereas female plantsproduce only seed. This type of biologyleads to cross-pollination, or the fertiliza-tion of female plants with pollen from oneor more male plants. Cross-pollinationcan greatly increase the genetic diversityof a population, and with genetic diversitycomes a wide range of morphological andbiological characteristics. Seeds producedby female waterhemp plants are small andusually germinate from very shallowdepths in the soil (0.5 inch or less). Thenumber of seeds produced by female wa-terhemp plants can vary depending onnumerous factors, but waterhemp is gen-erally considered to be a prolific seedproducer.

The germination and emergence patternsof waterhemp are characteristics that con-tribute significantly to managementproblems. Whereas the peak emergence ofother, more familiar annual weed speciesgenerally occurs during the early portionof the growing season, waterhemp emer-gence can easily occur during the middleto late portions of the growing season.Data collected at Iowa State University in1996 indicated that whereas velvetleafemergence was nearly complete by earlyJune, a significant number of waterhempplants emerged well into July. Obviously,this type of emergence pattern presentsmanagement challenges for soil-applied-only or postemergence-only herbicideprograms.

Identification

Accurate identification of the variousAmaranths can be challenging, especiallywhen the plants are in early vegetativestages. While each of the pigweeds previ-ously described is recognized as a distinctspecies and has unique identificationcharacteristics, hybridization among someof these species may produce offspringpossessing characteristics of each parent,further complicating identification. Thebest time to accurately identify the vari-ous Amaranths is when the plants are atthe reproductive stage with floweringstructures present.


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Waterhemp plants typically have no hairs

Table 3. Soybean herbicide premixes.Herbicide Components (ai/gal or lb) If you apply/A You have applied (ai) Product equivalents areAxiom 68DF flufenacet = 0.544 lb 13 ounces flufenacet = 0.442 lb flufenacet = 0.442 lb ai

metribuzin = 0.136 lb metribuzin = 0.111 lb Sencor 75DF = 2.36 ounces

Broadstrike metolachlor = 7.47 lbs 2.5 pints metolachlor = 2.33 lbs Dual 8E = 2.33 pints+ Dual 7.67E flumetsulam = 0.2 lb flumetsulam = 0.063 lb Python 80WDG = 1.25 ounces

Broadstrike trifluralin = 3.4 lbs 2.25 pints trifluralin = 0.956 lb Treflan 4E = 1.91 pints+ Treflan 3.65E flumetsulam = 0.25 lb flumetsulam = 0.07 lb Python 80WDG = 1.41 ounces

Canopy 75DG chlorimuron = 0.107 lb 6 ounces chlorimuron = 0.039 lb Classic 25DF = 2.56 ouncesmetribuzin = 0.643 lb metribuzin = 0.24 lb Lexone 75DF = 5.14 ounces

Canopy 58.3SP chlorimuron = 0.083 lb 7.7 ounces chlorimuron = 0.039 lb Classic 25DF = 2.56 ouncesmetribuzin = 0.50 lb metribuzin = 0.24 lb Lexone 75DF = 5.14 ounces

Canopy XL 56.3DG sulfentrazone = 0.469 lb 6.8 ounces sulfentrazone = 0.199 lb Authority 75DF = 4.25 ounceschlorimuron = 0.094 lb chlorimuron = 0.04 lb Classic 25DF = 2.56 ounces

Conclude B&G bentazon = 2.67 lbs 3 pints bentazon = 0.5 lb Basagran 4S = 1 pintacifluorfen = 1.33 lbs acifluorfen = 0.25 lb Blazer 2S = 1 pintsethoxydim = 1.5 lbs sethoxydim = 0.28 lb Poast 1.5E = 1.5 pints

Detail 4.1E imazaquin = 0.5 lb 1 quart imazaquin = 0.125 lb Scepter 70DG = 2.86 ouncesdimethenamid = 3.6 lbs dimethenamid = 0.9 lb Frontier 6E = 19.2 fluid ounces

Fusion 2.56E fluazifop = 2 lbs 8 fluid ounces fluazifop = 0.125 lb Fusilade DX 2E = 8 fluid ouncesfenoxaprop = 0.56 lb fenoxaprop = 0.035 lb Option II 0.67E = 6.7 fl oz

Galaxy 3.67S bentazon = 3 lbs 2 pints bentazon = 0.75 lb Basagran 4S = 1.5 pintsacifluorfen = 0.67 lb acifluorfen = 0.17 lb Blazer 2S = 0.67 pint

Manifest B&G bentazon = 3 lbs 3.5 pints bentazon = 0.75 lb Basagran 4S = 1.5 pintsacifluorfen = 0.67 lb acifluorfen = 0.17 lb Blazer 2S = 0.67 pintsethoxydim = 1.5 lbs sethoxydim = 0.28 lb Poast 1.5E = 1.5 pints

Pursuit Plus 2.9EC imazethapyr = 0.2 lb 2.5 pints imazethapyr = 0.063 lb Pursuit 2AS = 4 fluid ouncespendimethalin = 2.7 lbs pendimethalin = 0.84 lb Prowl 3.3EC = 2 pints

Reliance STS 25SP chlorimuron = 0.16 lb 0.5 ounce chlorimuron = 0.005 lb Classic 25DF = 0.32 ouncethifensulfuron = 0.09 lb thifensulfuron = 0.0028

lbPinnacle 25DF = 0.18 ounce

Rezult B&G bentazon = 5 lbs 3.2 pints bentazon = 1.0 lbs Basagran 4S = 2 pintssethoxydim = 1 lb sethoxydim = 0.20 lb Poast Plus 1E = 1.6 pints

Scepter O.T. 2.5E imazaquin = 0.5 lb 1 pint imazaquin = 0.06 lb Scepter 70DG = 1.43 ouncesacifluorfen = 2 lbs acifluorfen = 0.25 lb Blazer 2S = 1 pint

Squadron 2.33E imazaquin = 0.33 lb 3 pints imazaquin = 0.124 lb Scepter 70DG = 2.83 ouncespendimethalin = 2 lbs pendimethalin = 0.75 lb Prowl 3.3EC = 1.82 pints

Steel 2.59EC imazaquin = 0.17 lb 3 pints imazaquin = 0.063 lb Scepter 70DG = 1.46 ouncesimazethapyr = 0.17 lb imazethapyr = 0.063 lb Pursuit 2AS = 4 fluid ouncespendimethalin = 2.25 lbs pendimethalin = 0.84 lb Prowl 3.3EC = 2 pints

Stellar 3.1E lactofen = 2.4 lbs 5 fluid ounces lactofen = 0.094 lb Cobra 2E = 6 fluid ouncesflumiclorac = 0.7 lb flumiclorac = 0.027 lb Resource 0.86E = 4 fl oz

Storm 4S bentazon = 2.67 lbs 1.5 pints bentazon = 0.5 lb Basagran 4S = 1 pintacifluorfen = 1.33 lbs acifluorfen = 0.25 lb Blazer 2S = 1 pint

Synchrony STS42DF

chlorimuron = 0.318 lb 0.5 ounce chlorimuron = 0.001 lb Classic 25DF = 0.64 ounce

thifensulfuron = 0.102 lb thifensulfuron = 0.003 lb Pinnacle 25DF = 0.204 ounce

Tri-Scept 3E imazaquin = 0.43 lb 2.33 pints imazaquin = 0.125 lb Scepter 70DG = 2.86 ouncestrifluralin = 2.57 lbs trifluralin = 0.75 lb Treflan 4E = 1.5 pints

Turbo 8E metolachlor = 6.55 lbs 2.75 pints metolachlor = 2.25 lbs Dual 8E = 2.25 pintsmetribuzin = 1.45 lbs metribuzin = 0.498 lb Sencor 75DF = 10.63 ounces


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Waterhemp plants typically have no hairs(pubescence) on their stem and leaf sur-faces. In contrast, smooth and redrootpigweed have small, fine hairs on bothstem and leaf surfaces that make the plantfeel rough to the touch. The leaves ofwaterhemp plants are often glossy andmore elongated (lanceolate) compared toredroot or smooth pigweed. Stem color ofwaterhemp can vary from light green todark red, with multiple shades sometimeson the same plant. There does not appearto be a strong correlation between stemcolor and sex of the plant. Female plantsmay be completely red, completely green,or some combination of red and green.Male plants may exhibit a similar colorpattern.

Table 4 contains information for identifi-cation of the various Amaranth species.Other identification sources are available,and many contain color pictures that someindividuals may find helpful. One of thebest pigweed identification references is aguide that was jointly developed by Kan-sas State University, USDA/ARS, and theUniversity of Illinois. Pigweed Identifica-

tion: A Pictorial Guide to the CommonPigweeds of the Great Plains is availablefrom the Kansas State University Coop-erative Extension Service DistributionCenter, 16 Umberger Hall, Kansas StateUniversity, Manhattan, Kansas 66506-3406. This reference guide contains colorphotographs of the various pigweed spe-cies described in this article as well asbrief descriptions of both vegetative andreproductive characteristics.

Management Considerations

What is the best way to manage water-hemp in corn or soybean production sys-tems? Although there may not be any one“best” way, some methods may be muchmore consistent than others. Whereaswaterhemp may, in some instances, beadequately controlled by a single soil-applied or postemergence herbicide, thisis generally not considered the most con-sistent method to manage this weed. Themost consistent waterhemp managementprograms in either corn or soybean pro-duction systems consist of a sequentialmanagement approach. By sequential we

are referring to utilization of multiplecontrol options, including tillage, cultiva-tion, soil-applied herbicides, and poste-mergence herbicides. Although a singlepostemergence herbicide application maysometimes provide acceptable waterhempcontrol, this is the exception rather thanthe rule. Waterhemp may well be the“poster weed” for an integrated weedmanagement program.

Considerations with Soil-AppliedHerbicide Programs

Numerous soil-applied herbicides possessgood activity on waterhemp and othersmall-seeded species. Time of applicationcan have a significant impact on the suc-cess of soil-applied herbicides for water-hemp control. A common practice in no-till systems is to apply a herbicide severalweeks prior to planting in order to receivesufficient precipitation to incorporate theherbicide. Keep in mind, however, thatthe earlier a herbicide is applied, the ear-lier within the growing season the level ofweed control begins to decline. Water-hemp can emerge much later in the

Table 4. Pigweed identification characteristics.Species Hairs Leaves Flowers Seed HeadRedroot Small, fine Rounded Monoecious Highly branched, compact

Smooth Small, fine Rounded Monoecious Highly branched, < compact

Waterhemp Tall None Lanceolate Dioecious Top of plant and at leaf tips Common None Lanceolate Dioecious

Palmer Amaranth Few to none Poinsettia-like, “V”variegation

Dioecious Nonbranched, 1 to 2 feet long

Powell Amaranth Small, fine Tapered and slightlypinched at end

Monoecious Branched, < RR or smooth, 4 to 8 incheslong

Spiny Amaranth None “V” variegation, spinesat nodes

Monoecious Male toward top; female toward bottom

Tumble ? Egg-shaped, wavyedges, olive green

Monoecious No distinct flowering structure, flowers atnodes

Prostrate ? Spatulate, cotyledonslonger than others

Monoecious No distinct flowering structure, flowers atnodes

NOTE: Each of these species may have a reddish-colored root.Redroot vs. smooth: Differentiate only when seed head is present.Redroot/smooth vs. waterhemp: Differentiate by hairs, leaf shape, waxy leaves of waterhemp.Tall vs. common waterhemp: Differentiate by fracture of seed capsule (utricle): common = two sections, tall = irregular.


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growing season than is common for othersummer annual species. If the herbicidewas applied several weeks prior to plant-ing, it may not have sufficient residualactivity remaining to control a late-emerging species such as waterhemp.

What can be done to extend the length ofcontrol afforded by soil-applied herbi-cides? Here are three options:

q If allowed by label, increase the ratewhen applications are to be madeseveral weeks prior to planting.

q Apply the herbicide in a split appli-cation (generally two-thirds earlywith the remaining one-third atplanting).

q Apply the herbicide closer to plantingtime.

In our research, we have had better andmore consistent results with soil-appliedherbicides that were applied within 1 to 2weeks of planting or at planting comparedto the same herbicides applied severalweeks (up to 5 weeks) prior to planting. Itis not reasonable to assume that all soil-applied herbicides can be applied imme-diately before planting due to time andequipment restraints, but fields with asignificant waterhemp problem would beexcellent candidates for soil-applied her-bicide applications immediately beforeplanting.

Considerations with PostemergenceHerbicides

Similar to soil-applied programs, severalpostemergence herbicides are very effec-tive on waterhemp. The factors governingthe effectiveness of postemergence herbi-cides are critically important when deal-ing with waterhemp. Herbicide rate, ap-plication timing, and spray additive allinfluence how well postemergence herbi-cides perform against waterhemp.

Producers often like to wait as long aspossible to apply postemergence herbi-cides, especially those that lack any sig-nificant soil residual activity, in order tohave as many weeds emerged as possible.

Because waterhemp can germinate andemerge for an extended period of time, awide range of plant sizes typically existsby the time postemergence herbicides areapplied, which can present problems withspray interception by smaller plants underthe protective canopy of larger plants.Adjustments in spray volume and pressurecan help to overcome some of the prob-lem with coverage. Spray volumes of 20gallons per acre with application pressuresof 40 to 60 pounds per square inch gener-ally provide a uniform coverage of thetarget vegetation.

The next issue of the Bulletin will containmore information about waterhemp man-agement in corn and soybean productionsystems.—Aaron Hager, Loyd Wax, Mar-shal McGlamery

Spring Has Sprung, Fall Has Fell,Weeds Are Here as Usual

A mild winter (again) has given cool sea-son (winter annual) weeds a great oppor-tunity to survive and grow. This is evi-denced by the lush growth of chickweed,henbit, mustards (many species), speed-wells, prickly lettuce, marestail (officiallyhorseweed), and downy brome. This isalso true of winter annual crops or covercrops such as winter wheat, rye, and hairyvetch. Cool season perennials such asCanada thistle, curly dock, and dandelionhave weathered the winter quite well.Early summer annuals such as ragweeds(giant and common), smartweeds, andlambsquarters are joining the winter an-nuals and cool season perennials to pro-vide “ground cover.”

Know Your Enemy, Choose YourWeapons

The big no-till question revolves aroundwhat “burndown” treatment will controlthese weeds. 2,4-D is excellent on mostmustards, prickly lettuce, and marestail,but chickweed and henbit are not its forte.Dicamba (Banvel or Clarity) and atrazineare better on chickweed and henbit. Theforte of glyphosate (Roundup Ultra,Touchdown, Glyfos, Credit, etc.) is grass

control, but it can control many broadleafweeds at higher rates, and the addition of2,4-D or dicamba may also improvebroadleaf control. Gramoxone Extra aloneor with atrazine (improves mustard andsmartweed control) can also be used. Ta-ble 5 is reprinted from the 1999 IllinoisAgricultural Pest Management Handbookand provides ratings for various burndownherbicide options on several weed species.

Read the Label for 2,4-D Products

Even though the active ingredient may bethe same, not all formulations of 2,4-Dhave identical uses allowed on their re-spective labels. Always consult the labelof the 2,4-D product you intend to use forallowable uses, rates, and restric-tions.—Marshal McGlamery, AaronHager

PLANT DISEASES

Sampling for SCN—There Is StillSome Time

Predictive soil sampling and analysis forthe soybean cyst nematode (SCN) canprovide timely information for growers,especially those considering planting soy-beans this growing season. Growers canuse the analysis to select SCN-management strategies and tactics thatwill minimize losses. Fields to samplemight include those with an unexplaineddrop in yields of the last soybean crop or ahistory of stunted and perhaps yellowedsoybeans in spots or patches. Growersmay also want to sample to check nema-tode populations following 3- to 4-yearrotations involving the use of nonhostcrops and SCN-resistant varieties. Thischeck is especially important when theinitial population was determined to be ata moderate-to-high level (5 to above 25cysts per 100 cc of soil).

Although a fall sampling may be prefer-able, samples can still be collected inearly spring. However, you may find SCNfor the first time and thus need to quickly


29

change the crop or variety to be planted.So time is limited for this growing season.

Sampling procedures: For best results,take 12 to 24 subsamples (probes) in azigzag pattern through each 10 to 20 acresto be sampled. Collect soil to a depth of 6to 8 inches. Mix the soil and place ap-proximately 1 quart in a sturdy plasticbag; repeat for each 10 to 20 set.

Next, complete a nematode soil sampleform (available at your nearest Extensionoffice) and submit it with the packagedsamples. If no form is available, includean attached letter with (1) your name,address, county, and phone number; (2)any symptoms observed during previousplantings of soybeans and the patterns ofthe symptoms in the field (scattered,clustered in spots, or uniform); (3) theapproximate size of the area sampled; (4)the cropping history for at least 3 years;(5) herbicides or other pesticides used the

previous year; and (6) the crop or crops tobe grown this season. Send them to PlantPathology, N-533 Turner Hall, 1102 S.Goodwin Ave., Urbana, IL 61801. AfterMay 3 send samples to the Plant Clinic,1401 W. St. Mary’s Road, Urbana, IL61802.

For more information on sampling, referto the Report on Plant Disease Nos. 1100and 1107, available at Extension centersor from the Department of Crop Sciences(at the cost of $1.00 per copy) at theabove-mentioned Turner Hall ad-dress.—Dale I. Edwards

General Considerations forManaging Soybean Cyst Nematode

An ideal program to manage soybean cystnematode (SCN) infestations should inte-grate the following: detection throughscouting and sampling procedures and

crop rotations utilizing nonhost crops andSCN-resistant soybean varieties. Main-taining proper soil fertility and pH, man-aging other soybean diseases and pests,and proper planting methods also help tokeep plants vigorous and better able tobuffer the effects of SCN. The most ef-fective management systems have andwill continue to involve integrated ap-proaches. No single method will manageSCN as effectively.

The success story of managing SCN hasbeen the use of resistant varieties. Twentyyears ago, only a small number of varie-ties that resisted SCN were available. To-day, through the efforts of public and pri-vate soybean breeders, this list hasexpanded to approximately 530 linesadaptable to Illinois and available for the1999 growing season. Marion Shier,Crops Systems Educator, LivingstonCounty, compiles yearly a list of public

Table 5. Control ratings for no-till herbicides for control of existing vegetation.Annual grasses Annual broadleaf weeds Perennial broadleaf

DBM GFT RYE LQR PLC MTL MUS CRW GRW SWD ALF RCV DDL HVCglyphosate -12a

9 9 8 8 7 7 8 7 8 7 5 6 5 6

glyphosate -24b

9+ 9+ 9 9 8 9 9 9 9 8 6 7 7 7

glyphosate+2,4-D

9 9 9 9 9 9 9 9 9 8 7 8 8 8

Gramoxone 7 8 6 8 6 6 7 8 7 5 N 6 4 6Gramoxone+atrazine

8 9 8 9 9 9 9 9 9 9 4 7 6 8

2,4-D Ester 1pt N N N 9 8 8 9 9 8 6 6 8 8 8Banvel/Clarity N N N 9 9 7 7 9 9 9 8 9 7 92,4-D +Banvel N N N 9 9 8 9 9 9 8 8 9 8 9Marksman 6 5 N 9 9 9 8 9 9 9 8 9 7 9Atrazine 7 7 6 9 9 8 8 9 9 9 N 6 4 7Balance 6 8 5 8 8 8 8 8 6 8 N N 6 NCanopy N 5 N 9 9 8 9 9 8 9 4 5 7 5Canopy XL N 6 N 9 9 9 9 9 8 9 N 4 4 6Sencor/Lexone 5 5 4 7 8 6 8 7 6 8 N 5 6 5DBM = downy brome, GFT = giant foxtail, RYE = rye or wheat cover, MTL = marestail (horseweed),MUS = mustards, PLC = prickly lettuce, LQR = lambsquarters, CRW = common ragweed,GRW = giant ragweed, SWD = Smartweed, DDL = dandelion,HVC = hairy vetch, RCV = red clover, ALF = Alfalfa sod

Control ratings: 9 = excellent , 8 = good, 7 = fair, 6 = poor, 5 or 4 = unsatisfactory, N = nil or none.Boldface indicates acceptable control.aglyphosate 12 oz a.e./A = 16 fl oz/A Roundup Ultra or 14.5 fl oz Touchdown 5bglyphosate 24 oz a.e./A = 32 fl oz/A Roundup Ultra or 29 fl oz Touchdown 5


30

and private varieties resistant to SCN. Allvarieties include a listing by maturitygroup and relative maturity within thegroupings; a coding system that desig-nates companies making the variety avail-able; and a listing of race resistance andsource of resistance for each variety. TheIllinois Checkoff Board has published thislisting in booklet form, and free copiesmay be obtained by contacting:

The Illinois Soybean Checkoff Board1605 Commerce ParkwayBloomington, IL 61704Telephone: (309)663-7692FAX: (309)663-6981E-mail: [email protected]

Resistant varieties are the foundation forIPM approaches in managing SCN as wellas other plant diseases. Some distinct ad-vantages of using host resistance are thatthe pest control is purchased with theseed, it is compatible with other manage-ment practices, it has few adverse effectson the environment, and the cost is mini-mal in most cases.—Dale I. Edwards

Recognizing Corn NematodeProblems

Corn nematode damage may become evi-dent 2 to 4 weeks after seedling emer-gence but is most pronounced in late Mayand June. Above-ground symptoms usu-ally include plant patches that are yel-lowed, stunted, or both. Symptoms ofdrought or nutrient deficiency may occurfirst in nematode-damaged areas duringperiods of water stress, high temperatures,or both. Because nematodes can damagecorn without showing above-groundsymptoms, they may be overlooked. Agradual decline in corn yield over a periodof years may indicate a nematode prob-lem. When plants are dug up, the rootsmay appear discolored; lateral roots maybe short, stubby, and lacking fine feederroots; and overall root systems may bereduced. Root symptoms caused by nee-dle and dagger nematodes often resembledinitroaniline herbicide injury. Table 6lists nematodes that may be associatedwith corn, the types of damage they cause,and other host plants.

In Illinois, nematode damage to corn hasbeen more severe where corn has beencropped continuously for three or moreyears on sandy soils. Needle, dagger, andlance nematodes are favored by theseconditions. When nematodes are sus-pected, soil and root samples must beanalyzed to confirm the problem. Reporton Plant Disease No. 1100 gives detailedinformation on how to collect and shipsoil samples for nematode analysis.

The use of crop rotations or nematicideswill be of little value for corn alreadyplanted. However, an awareness of cornnematode problems is essential for plan-ning control strategies for the next grow-ing season. For planted corn, try, if possi-ble, to maintain optimum growingconditions; nematode damage is greateron plants stressed by other factors. Dam-age can be reduced greatly by providingplants with adequate moisture (especiallyon sandy, irrigated soils), nutrients, andsoil aeration at all times. Controlling otherdiseases and insects also reduces plantstress. For more information on corn

Table 6. Nematodes associated with corn in Illinois.Genus Importance* Type of damage Other host plantsPratylenchus(Root-lesion)

1-B Smaller-than-normal root system,darkened and discolored roots,moderate stunting

Grasses, cereals, legumes, vegetables, treefruits, strawberry, pines (host range varies fordifferent species of root-lesion nematodes)

Hopololaimus(Lance)

2-B Reduced root system, darkenedand discolored roots, moderatestunting, and chlorosis

Grasses, legumes, tomato, pepper, pines, manyothers

Xiphinema(Dagger)

2-B Severe stunting, chlorosis, fewfine feeder roots

Grasses, legumes, ornamentals, strawberry,trees, many others

Helicotylenchus(Stunt)

1-C Smaller-than-normal root system,moderate stunting, chlorosis

Grasses, cereals, legumes, tomato, many others

Longidorus(Needle)

2-A Severe stunting, chlorosis; severeroot pruning; root system consistsmainly of short, stubby, thickenedside roots that appear somewhatswollen

Members of the grass family, potato, grape, andmany others

Trichodorus(Stubby-root)

3-A Stubby lateral roots, coarse roots,excessive upper roots, severestunting, chlorosis

Grasses, legumes, tomato, potato, beet, orna-mentals, many others

*The number indicates how commonly the genus is involved in nematode problems in Illinois: 1 = very common; 2 = occasionally; 3 =rarely. The letter indicates its potential for damage: A = very damaging; B = moderately damaging; C = damaging only at high popula-tions.


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nematodes, see Report on Plant DiseaseNos. 1103 and 1106, available for $1.00each from the Department of Crop Sci-ences, University of Illinois, N-533Turner Hall, Urbana, IL 61801, (217)333-8375.—Dale I. Edwards

Dale I. Edwards([email protected]),Nematologist, Department of CropSciences, (217)244-2011

Mike Gray ([email protected]),Extension Entomology, (217)333-6652

Aaron Hager ([email protected]),Extension Weed Science, (217)333-4424

Marshal McGlamery([email protected]),Extension Weed Science, (217)333-4424

Bruce Paulsrud ([email protected]),Extension Specialist/Pesticide ApplicatorTraining/Plant Pathology, (217)244-9646

Kevin Steffey ([email protected]),Extension Entomology, (217)333-6652

Loyd Wax ([email protected]), WeedScientist, USDA/ARS, (217)333-4424

Contributing Authors

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