Volume 24 No. 2 April 21, 2017

Contents...

Scouting Report

Conifers (As Christmas & Landscape

Trees): Bagworms, Balsam Woolly Adelgid, Cyclaneusma Needlecast, European Pine Sawfly, Pine-Pine Gall Rust, Southern Pine Beetle, Spruce Spider Mite ..................................5

Conifers (As Landscape Ornamentals):

Arborvitae Leafminer, Juniper Scale, Juniper Webworm, Larch Casebearer ...................................6

Broad-leaved: Boxwood Blight, Boxwood Leafminer, Boxwood Mite, Calico Scale, Dogwood Borer, Eastern Tent Caterpillar, Euonymus Scale, European Fruit Lecanium Scale, Privet Rust Mite, Twolined Chestnut Borer ..............................6

Feature Article: Oyster-Shaped Scales .................................... Insert

Things to Look For: Dogwood Anthracnose, Forest Tent Caterpillar, Gypsy Moth, Hickory Gall Phylloxera, Lilac Borer, Spruce Budworm, Zimmerman Pine Moth ................7

Phenology- .....................................8

Growing Degree Days ................8

spring and early summer. Infected two- and three-year-old needles become light tan to brown, develop transverse bands, and are prematurely cast from the tree. This disease has no apparent effect on tree health and is only worth managing for aesthetic purposes. Therefore, landscape pines with unacceptable levels of Cyclaneusma probably ought to be removed unless they are so important that one is prepared to invest in treatments for the rest of the life of the tree. Where this fungus has become a problem in Christmas tree plantations, treat with a registered fungicide at budbreak. Then make additional applications at 6 – 8 week intervals through October, and treat only those trees that are within two years of harvest.

European Pine Sawfly (2)—The 2017 crop of pine sawfly larvae have just hatched in the NY City area according to Don Gabel, from the New York Botanical Garden. The young sawflies are grayish green with white markings and black heads. The best way to find them now is usually to look for a small area of straw colored, partially chewed needles. These tiny larvae will cause little damage early but as they grow, these gregarious feeders may cause significant defoliation. In fact, whole trees may be stripped in an unusually heavy infestation. When the larvae reach maturity, they will be about ¾ to 1-inch long. They feed only older needles and remain active until mid-June. This insect is an important pest of red, Scots, Japanese red, jack, Swiss mountain, and mugo pines. Only rarely are insecticides needed. Because the larvae feed in colonies, it is possible to spot-treat infested areas or handpick small populations.

Scouting ReportConifers(As Christmas & Landscape Trees)

Bagworms (80, 81)—Inspect cedar, arborvitae, juniper and other conifers for the spindle-shaped bags attached to the twigs and foliage. Foliage on heavily infested trees may be sparse. In light infestations, hand pick and destroy these bags containing the overwintering eggs. A single bag may contain between 300 – 1,000 eggs, so by manually removing them you will help reduce the population and may eliminate the need to spray. If a bag feels empty it was probably the home of last year’s male bagworm.

Balsam Woolly Adelgid (30)—Scout now for damage symptoms of this pest including yellowing of needles, “gouting” (swelling) of twigs, and stunted growth of leader. Balsam and Fraser fir are the most susceptible species of fir grown as Christmas trees in the Northeast but other true firs serve as hosts as well. This adelgid is a non-native pest that closely resembles the hemlock woolly adelgid. When populations are high, the bark of the trunk and major branches appears to be covered by snow because of the white tufts of waxy filaments produced by the adelgids. Lighter infestations can often be managed with pesticide sprays timed for bud-break. Heavily infested trees are not marketable, and should be removed and burned during the winter, when crawlers are not active.

Cyclaneusma Needlecast (26)—The pathogen here, which attacks mainly Scots pine, can cause new infections at any time that the air temperature is above freezing. However, most infection occurs in the

6—Branching Out

Pine-Pine Gall Rust (151)—Now is a good time to prune the galls on infected trees before the galls have a chance to produce spores. Pine-pine gall rust occurs on two and three needle pines, especially Scots and rarely Austrian and mugo. Most galls vary in size from that of a golf ball on small branches to as large as a softball when developing on the stem. Within the next few weeks the galls will split open to reveal masses of bright orange powdery spores that may easily be dispersed by the wind.

Southern Pine Beetle (25)—This pest has caused major losses of forest pines on Long Island in the last couple of years. Hosts include pines (pitch, white, red, Scots, others) and Norway spruce. Hemlocks are rarely attacked. Symptoms include numerous dime- to nickel-size white to reddish pitch tubes on trunk from base to 60 ft., reddish boring dust on bark, fading foliage from yellow-green to reddish brown, numerous (1⁄16") exit holes, as well as winding S-shaped galleries in cambium. Treat around late April (just prior to adult emergence) for bark treatment, or do a trunk injection in early April or in the fall.

Spruce Spider Mite (52)—Amy Albam and Jerry Giordano, from Westchester County CCE report these mites are active in the southern part of the state. The newly hatched spider mite nymphs have only six legs. Later stages will have eight legs. Their hosts include many conifers with damage common on spruce, pine, true firs, arborvitae and hemlock. If necessary apply insecticidal soap, horticultural oil, or other registered pesticide at 192 – 363 GDD50.

Conifers(As Landscape Ornamentals Only)

Arborvitae Leafminer (14)—Arborvitae leafminer (ALM) is an annual pest in nurseries and landscapes around the region. Dan Gilrein, reports “Calls often come in around this time when damage is most apparent, but this is not a time when treatments will be effective. Most of the damage is done for the year and the miner larvae, the caterpillar stage of a small moth, will be pupating in the mines soon. Damage from last summer and fall can persist and increase into the following spring, so if treatments were made last growing season check foliage for live miners. Samples I checked this winter from a nursery and from a residential site showed areas where treatments were highly effective and others where control needs to be scheduled. Although infested

plants will start to look better once new growth starts, the appearance will again deteriorate by late summer as damage from the next generation develops. Careful examination under magnification can also easily distinguish tip damage from ALM vs drought stress, pathogens and other causes. Time a foliar insecticide for the leafminer adults when active around late June using Conserve/Entrust, or other labeled contact insecticide (see Cornell Guidelines). If that timing is missed we have found summer and even early fall application of acephate (Acephate 97UP has a 2(ee) label in NY for ALM) can be effective. I suggest including a wetting agent in any treatment. Wet foliage thoroughly from all sides.”

Larch Casebearer (11)—The larvae of the larch casebearer were just becoming active in Westchester County according to Amy Albam and Jerry Giordano. Affected needles are brown at the tips or bleached. It is very difficult to find the larvae themselves because they are camouflaged in the straw colored needles they are mining. Damage is usually aesthetic but with a heavy infestation, premature defoliation is possible. With repeated defoliation, the growth of the tree is retarded, branches die, and the tree may be killed. In the Northeast, natural enemies attack this pest but don’t keep them in check. Therefore, if the population of larch casebearer is cause for concern, a pesticide application may be warranted. Treat in late April through early May, coinciding with the blooming of Japanese quince.

Broad-leaved Trees and Shrubs

Boxwood Blight—Initial symptoms of this fungal disease appear as dark or light brown spots on the leaves. Eventually the entire leaf will turn brown and fall off. Boxwood stem tissue will also have black streaking under the bark. Eventually the disease can kill infected boxwoods. English and American boxwood are highly susceptible. Pachysandra and sweetbox (Sarcococca sp.) are also hosts. If you suspect plants have this disease it is best to get it confirmed by a plant disease diagnostic laboratory. Protect nearby boxwood with registered fungicides in advance of rainy periods in spring and fall.

Boxwood Leafminer (94) and Boxwood Mite (229)—With the threat of boxwood blight more attention is paid to boxwoods and demand for local-grown material has increased. Dan Gilrein writes “During a recent nursery visit plants appeared healthy but with noticeable boxwood mite injury. Random samples collected from all varieties were checked under magnification, but had no overwintering eggs so I saw little reason to apply dormant-stage oil. There have been more complaints about boxwood mite in recent years on landscape and nursery plants, not necessarily associated with systemic

Arborvitae leafminer damage & adult © D. Gilrein

Boxwood mite damage looks like small scratches on the leaves © D. Dailey O'Brien

Juniper Scale (46)—Look for adult females overwintering on needles. Each is circular (about 1⁄16 inch diameter) and white and is commonly described as looking like a fried egg. ‘Pfitzer’ juniper is especially susceptible to this scale. In addition to juniper, arborvitae and Leyland cypress are also hosts. Light infestations cause no apparent damage, but heavier ones cause the foliage to turn yellow and dieback may occur. For heavy infestations, use a dormant oil spray in mid-April to early May (22 – 148 GDD50).

Juniper Webworm (8)—Infested junipers have brown foliage and twigs that are webbed together. Look inside this webbed foliage for the larvae. Young larvae mine needles, and the mature larvae consume the needles. When mature, the larvae are ¾ inch long, tan with brown stripes, black heads, and black legs. Several natural enemies keep this pest in check. Prune out infested branches. If numerous larvae are detected, treat in late April for overwintering larvae. Make sure to cover the foliage and not just the webs when making an application. Spray material must get past the webs and impinge on the foliage. ‘Pftizer’ and ‘Savin’ junipers are apparently resistant so if you are installing new plantings, consider these.

Branching Out—7

imidacloprid applications for leafminer. Watch through summer for the fine, white ‘etching’ on new foliage to determine if treatment is needed.” Dan continues “Leafminer is an even greater concern, however and I am often asked about management options. Resistant varieties (like ‘Newport Blue’ and ‘Vardar Valley’) is the best approach for managing leafminer. There are complaints about availability and slower growth compared with the more popular susceptible types. Some nurseries may work with you directly to propagate and grow specific varieties or provide liners for field production. For susceptible varieties with infestations time foliar applications for adults in spring or for young miners in early to mid-summer. Systemic insecticides containing imidacloprid can also be applied to soil in fall or early spring. For adults use abamectin (Avid or generic), imidacloprid (Merit 2F for landscapes, Discus N/G or Marathon II for nurseries, plus other formulations or generic versions of these), TriStar SL (reduced-risk), malathion, or M-Pede Insecticidal Soap. M-Pede provides no residual activity so repeat applications are needed to knock down adults as they appear. Summer foliar treatments with imidacloprid or TriStar can be used to control young miners. One trial found malathion applied about 6 weeks after adult emergence effective against miners in leaves. Include a penetrating surfactant with foliar applications and direct sprays towards leaf undersides. Abamectin, M-Pede and some other materials (spinosad, azadirachtin) do not control boxwood leafminers within leaves. In a trial last year we found spinosad (Conserve, Entrust) was also ineffective timed for adults. Annual application is probably not needed where treatments have been effective.”

Calico Scale (169)—This scale overwinters as nymphs on the twigs of its hosts including many popular woody ornamentals. Where practical, brush off the scales before crawlers emerge in mid-summer. If this pest is a problem, treat in mid-April to May (35 – 145 GDD50) for dormant treatment.

Dogwood Borer (123)—Set up your traps in mid-April to begin monitoring if you have had problems with this pest in the past. Note that the dogwood borer may not respond to the same lure in different parts of its range, so the value of the pheromone trap may be limited depending on where you live. If an insecticide treatment is warranted apply in mid-May to mid-June (148 – 700 GDD50).

Eastern Tent Caterpillar (76)—Small nests of this caterpillar are now visible on flowering crabapples in downstate NY according to Don Gabel and we would expect to see them elsewhere in the state in the next two weeks. The small larvae gather at the crotches of the tree, spinning a mass of webs that expand as the caterpillars grow. If practical destroy the tents containing caterpillars. The larvae usually prefer crabapple, wild cherry, and apple. When mature, each caterpillar is black with a white stripe between two darker longitudinal lines. Apply Bacillus thuringiensis while the larvae are still young, in late April through the first two weeks of May (90 – 190 GDD50) in order to prevent extensive damage before the caterpillars mature. Other pesticides are also registered for use. In the fall and winter, get rid of any egg masses.

Euonymus Scale (186)—The fertilized adult females have black, oyster-shell shaped, ⅛ inch long scale covers and can be found overwintering on bark of susceptible plants. Horticultural oil treatments (35 – 120 GDD50) are effective for light infestations. Treat crawlers in June 533 – 820 GDD50.

European Fruit Lecanium Scale (174)—Immature female scales overwinter on the twigs and limbs of their multiple hosts. Young stressed plants and newly transplanted plants are more susceptible. Honeydew and sooty mold may develop with large scale populations. In addition, growth may be stunted, leaves may drop, and shoots may dieback. If necessary treat in mid-April to early May (35 – 145 GDD50).

Privet Rust Mite (231)—The privet rust mite was a serious pest in landscapes and nurseries on Long Island last year. Dan Gilrein writes “Infestations can build to high levels causing foliage to become stunted and distorted. On sheared hedges leaves turn yellow and drop, leaving bare areas. The mites overwinter on the plants, so a dormant-stage oil can be used. While I don’t have data showing efficacy for this particular pest, oil is used for and does control other eriophyid mites overwintering on their hosts. As new growth appears abamectin (Avid or generic) plus 0.5% horticultural oil or non-ionic penetrating surfactant or wetting agent can be applied. I would suggest waiting until there are several inches of new growth to intercept the spray. Carbaryl can also be used but coverage needs to be very thorough with this material; abamectin has translaminar activity and is more ‘forgiving’.”

Twolined Chestnut Borer (127)—Oaks in some areas of the Northeast have suffered heavy defoliation from gypsy moth for a second year in a row. Aggravated by drought, this sets up oaks for attack by secondary pests like Armillaria root rot and twolined chestnut borer (TLCB). Dan Gilrein reports “Following the two last gypsy moth outbreaks I saw heavy attacks by TLCB in newly set oak liners in nurseries. The borer population appears to be elevated where oaks are weakened with the infestations ‘spilling over’ from forests into managed areas. These young trees are planted in spring, with no time to become established before the borers emerge. During the last siege one nursery lost over 600 trees. While most trees didn’t die, the wounding and galleries remaining in the bark rendered them unmarketable. In areas where TLCB levels may be high due to oaks under stress from drought and/or defoliation, it may be wise to plan on protecting newly planted nursery or landscape trees with a protectant bark spray before the adults emerge (around late May in southeastern NY), repeating after 2 weeks. Control options are listed in the Cornell Guidelines.” More information on TLCB can be found at http://www.na.fs.fed.us/Spfo/pubs/fidls/chestnutborer/chestnutborer.htm

Twolined chestnut borer damage & adults © D. Gilrein

Things to Look For in the Upcoming WeeksDogwood Anthracnose (52)—Flowering dogwood trees, Cornus florida, threatened by dogwood anthracnose must be sprayed soon after the first leaves emerge. There is a lot of tree-to-tree variability in leaf emergence.

Forest Tent Caterpillar (76)—These will be hatching soon. If necessary apply a registered pesticide at 192 – 363 GDD50.

Gypsy Moth (61,62)—Expect eggs to hatch soon in the lower Hudson Valley; and a couple of weeks thereafter farther north. Where an outbreak is of concern, be ready to treat with Bacillus thuringiensis subsp. Kurstaki and aizawai beginning in late April (90 – 448 GDD50).

8—Branching Out Dawn Dailey O'Brien,George W. Hudler & Dan Gilrein, editors

Hickory Leaf Stem Gall Phylloxera (222)—If management is warranted treat in late April to mid-May (91 – 246 GDD50) with dormant oil to control the overwintering eggs.

Lilac Borer (122)—Set out the sex pheromone traps soon to monitor and determine spray date. Make an application ten days after the first male moth is caught. Treat in mid-May (200 – 299 GDD50).

As of April 18, 2017Growing Degree Days

Station GDD50

Albany ................................83Binghamton ........................61Boston, MA ........................83Bridgeport, CT ...................74Buffalo ...............................51Central Park .....................161Farmingdale (4/13)...............39Hartford, CT .......................82

Station GDD50

Ithaca ..................................59New Brunswick,NJ ...........142Riverhead (4/13) ..................37Rochester ............................76Syracuse .............................63Watertown ..........................45Westchester ........................84Worcester, MA ...................68

Our Financial SupportersThis issue was made possible with the generous gifts from the following:

Almstead Tree, Shrub & Lawn Care Co.Bill deVosJon HickeyAnthony LegatoNew York State Turfgrass Association New York State Arborists-ISA Chapter Perennial Charm NurseryLorraine BallatoTim Blenk Tree CareJohn T. Campanini Jr.Cayuga Landscape Co., Inc.James CodyCharles Soulias Tree Care, Inc.Budd DaubmanEcology Tree, Inc.James HuntProfessional Tree Surgeons SupplyFran Reidy

PhenologyRockland/Westchester Counties:Flowering—American plum, birch (black, river, European white), Bradford pear, bridal wreath spiraea, Japanese quince, Korean spicebush viburnum, Norway maple, PJM rhododendron, redbud, sassafras, saucer magnolia, star magnolia, sugar maple, weeping willow

Tompkins County:Flowering—Amelanchier, forsythia, Norway maple, PJM rhododendron, red maple

Spruce Budworm (7)—If necessary a registered pesticide may be applied in late April through mid-June. Spruce budworms attack true firs and Douglas fir as well as spruces.

Zimmerman Pine Moth—If this pest has been a problem for you in the past, apply bark sprays with a registered pesticide in late April through mid-May (121 – 246 GDD50).