Please Note: Where a specific product is listed after a recommended pesticide, only that product is labeled for that use. Not all products listed are labeled for all uses, so be certain you are getting the right formulation (with the use(s) you want), before you purchase the pesticide.

Note:This information is valid for New York. It may or may not apply in your area.

The Scouting Reports list chemicals registered for control of specific pests. Our recommendations are taken from the 2005 Pest Management Guide  for Commercial Production and Maintenance of Trees and Shrubs. These recommendations apply to New York State.

The recommendations given in Branching Out  are not a substitute for pesticide labeling. Read and follow the label before applying any pesticide!

Scouting Report

Spittlebugs and their frothy white masses are numerous and very visible now. Two species are common in New York State. The pine spittlebug attacks pine, native spruce, balsam fir, Douglas-fir, and hemlock. On the other hand, the Saratoga spittlebug feeds only on red and jack pine. The Saratoga spittlebug, the more damaging of the two, also causes yellowing of foliage and may kill twigs, branches, and eventually a whole tree. Light infestations may be removed with a strong stream of water. However, it is too late to use insecticides to manage these insects this year.

Link to an INFORMATIVE WEBSITE regarding Spittlebugs placed on the web by North Carolina Cooperative Extension Service.

Link to a web page with a good photo of a spittlebug mass placed on the web by Purdue University Plant & Pest Diagnostic Lab.

Weir’s Cushion Rust (a.k.a Spruce Needle Rust)—This highly contagious needle rust on spruce, especially Colorado blue spruce, is easily visible now in Christmas tree plantations and – rarely – in landscapes. The pathogen, Chrysomyxa weirii, was declared a public nuisance in Pennsylvania when it first appeared there about 15 years ago. In a few cases, diseased landscape trees were destroyed on site to prevent spread to other trees, but the pathogen continues to show up sporadically throughout the Northeast. Unusually wet spring weather in ’04 apparently provided the right conditions for abundant symptoms now. Management with chemicals is the only option and chlorothalonil is the best choice to date. However, even that material will not eradicate the disease. The Pennsylvania Department of Agriculture continues to take a firm stance on this disease. If you are shipping blue spruce to PA, be sure the trees are spotless with regard to rust or expect to have them rejected. Unfortunately, good pictures on the WWW are hard to find. We’ll try to run some for our next issue and will post them when the web version of this issue goes up. Link to an INFORMATIVE WEBSITE regarding Weir's cushion rust found on the web at the Christmas Tree IPM Pest web page sponsored by the Department of Plant Pathology at Cornell University.There are several good photos on this site.

Apple Scab (43)—Foliar spots from this common disease, caused by the fungus Venturia inaequalis, are starting to appear. The lesions are olive green, circular with uneven margins. With time, the lesions enlarge, darken and turn velvety. With heavy infections, the leaves may curl, cup or become dwarfed. Lesions may also be seen on the fruit where they appear as rough, dark green areas. Although the first cycles of the disease have already caused significant infection some protection will be provided by applications of appropriate fungicides starting now.Link to an INFORMATIVE WEBSITE regarding Apple Scab placed on the web by West Virginia University

Link to an INFORMATIVE WEBSITE regarding Apple Scab placed on the web by Ohio State University Extension

Ash Anthracnose (48)—We saw ash anthracnose on our recent scouting trip to Orange County. It affects black, white and green ash. Leaves first develop water soaked areas and later irregular, necrotic blotches and leaflet distortion. The blotches enlarge and coalesce rapidly and the leaves drop. Entire flushes of shoots may be killed in wet years and the damage is often mistaken for late spring frost damage. Defoliation from ash anthracnose occurs so early in the season that affected trees seem to have plenty of stored reserves to produce a second flush of leaves.

    Repeat infections are made by the spores as long as the conditions are cool and wet, but as summer approaches disease incidence is usually reduced. Unfortunately, it is too late to treat this year. As a control measure destroy or compost fallen leaves. Choose resistant green ash instead of highly susceptible white ash where disease pressure is high.Link to an INFORMATIVE WEBSITE regarding Ash Anthracnose placed on the web by Iowa State University Extension. There are good photos on this site.

Bacterial Blight of Lilac (75)—Symptoms caused by Pseudomonas syringae were seen on the last scouting trip. Bacterial blight of lilac is characterized by death and shriveling of leaves, shoots, and sometimes flower clusters.  At high elevations and in colder valleys, late frost this year could cause similar symptoms. Chinese, Japanese, Persian, and common lilacs, especially white-flowering types, are susceptible. Pruning prevents dense growth of the infected plant. Cut out and destroy infected shoots as soon as symptoms appear, disinfecting the tools between cuts. Link to an INFORMATIVE WEBSITE regarding Bacterial Blight of Lilac placed on the web by the Cornell Plant Disease Diagnostic Clinic.

Boxwood Leafminer (94)—We saw the boxwood leafminer adults on our last scouting trip to Westchester County and Long Island. They are small orange, gnat like flies. They should now be laying their eggs in the tender leaf tissue, but the new leaves do not show signs of mining until later in the summer when the larvae are larger. Injury is caused when the larvae feed in the soft parenchymal tissue. Mined or blistered leaves are evident from midsummer until the leaves are shed from the plant. An imidacloprid soil drench or injection in late summer might be the best IPM approach. The other management option is to spray with a registered pesticide between 350 and 600 GDD50.

Link to an INFORMATIVE WEBSITE regarding Boxwood Leafminer placed on the web by North Carolina Cooperative Extension Service. There are some good drawings on this site.

Link to a good photo of Boxwood Leafminer adults placed on the web by North Carolina Cooperative Extension Service.

Link to a web page with a good photo of Boxwood Leafminer damage placed on the web by Clemson University.

Boxwood Psyllid (137)—The adults of the boxwood psyllid are now present. They are green and somewhat flattened, with posterior fluffy white wax. They feed on the inside of the cupped terminal leaves. American boxwood cultivars, except ‘Suffruticosa’, are preferred and most seriously damaged by this imported psyllid. English boxwoods rarely receive serious damage. The terminal shoots of these plants are infected and develop cupped leaves that are normal colored but may be stunted. This is an aesthetic problem and treatment is not usually necessary. If damage is so severe that treatment is warranted try horticultural oil or insecticidal soap late May, 290-440 GDD50..Link to an INFORMATIVE WEBSITE regarding Boxwood Psyllid-placed on the web by University of Mass. Extension. There are good photos on this site.

Link to a good photo of boxwood psyllid adults placed on the web by Virginia Cooperative Extension.

Cedar Apple Rust (118, 119)—Bright yellowish orange spots have begun to appear on the leaves of crabapples. On the upper surfaces of the leaves, tiny pustules are located within the spots. Circular lesions can be seen on the lower surface of the leaf, with the aid of the hand lens. Nothing can be done now to treat this disease now. However, be prepared to treat infected trees next spring. In the future, plant rust resistant varieties.

Downy Leaf Spot of Hickory (54)—Symptoms of this disease are just becoming apparent on hickories throughout the state. The fungus sporulates on lower leaf surfaces in a dense white mat of fungal tissue that vaguely resembles erineum galls and results in conspicuous yellow spots as viewed from above. This disease is caused by the fungus Microstroma juglandis. Its hosts include butternut and bitternut, pignut, and shagbark hickories amongst others. Premature defoliation may occur if conditions for disease development are especially favorable as they have been this year. Generally, it is of little consequence.Link to additional photos of Downy Leaf Spot of Hickory placed on the web by Iowa State University Extension

Elm Leafminer (85)—We saw the elongate, interveinal blotch mines on elm leaves during our scouting trip. This leafminer attacks Scots, Camperdown, English and American elms. If populations are at an unacceptable high level you can treat with registered materials in mid-May to early June (263-530 GDD50)

Elongate Hemlock Scale (45) —We found the crawlers of elongate hemlock scale on our last scouting trip. The crawlers are bright, lemon yellow and 0.1mm long. It is a serious pest of hemlock and the also attack yew, spruce, and Douglas-fir. Their feeding causes needles to yellow and drop prematurely. Treat heavily infested plants in late May through mid-June (360-700GDD50). Link to an INFORMATIVE WEBSITE regarding Elongate Hemlock Scale placed on the web by Penn State Cooperative Extension.

Link to some good photos of Elongate Hemlock Scale placed on the web by the Bugwood Network.

Four-lined Plant Bug (190)—The four-lined plant bug nymph and its feeding damage have been seen throughout the state. The nymph’s color ranges from bright red to yellow and the forewings on the adult are yellow but may turn green. However, the four black stripes remain distinct. Woody ornamentals that serve as food for this insect include azalea, deutzia, dogwood, forsythia, viburnum, weigela, rose amur maple, and sumac. It also feeds on many herbaceous plants. Feeding injury to upper surfaces of leaves by both nymphs and adults generally takes the form of discrete circular spots that may be visible from above. Injured areas may turn black or become translucent, and after several weeks the remaining necrotic tissue may drop out leaving small holes. On shrubby plants the topmost leaves are the first to be injured. Link to an INFORMATIVE WEBSITE regarding Fourlined Plant Bug placed on the web by Purdue University.

Link to a good photo of a Fourlined Plant Bug Nymph placed on the web by Ohio State University Extension.

Gypsy Moth (61,62)–We’ve seen the first and second instar gypsy moth caterpillars crawling around the state on a variety of deciduous trees. If populations are not being controlled by natural enemies apply Bacillus thuringiensis subsp. kurstaki when the larvae are first detected. Alternatively, other pesticides are registered for use from 90-448 GDD50.

Native Holly Leafminer (95)—The small black flies (1/8 inch long) can be found around the newly expanded leaves. Examine young foliage of English and American holly for tiny green blisters. Because the parasites do not reduce the area mined and the resulting aesthetic damage, they can not be relied upon. Place a sticky trap on the terminals of holly to detect the adults. To manage large adult populations, apply a contact insecticide in mid-May (192-298 GDD50).

Link to an INFORMATIVE WEBSITE regarding Native Holly Leafminer placed on the web by Penn State Cooperative Extension. There are some good photos on this site.

Link to an INFORMATIVE WEBSITE regarding Native Holly Leafminer placed on the web by the Center for Integrated Pest Management, North Carolina StateUniversity. There are several good drawings on this site.

Oak Leaf Blister (6)—This disease is caused by Taphrina caerulescens and is starting to cause leaf blisters on red oaks around the state. Symptoms include bulges or depressions usually 1⁄8 to 3⁄4 inch across on either leaf surface. These may cause severe curling on leaves, and numerous blisters may come together and involve entire leaves. The disease rarely causes enough damage to warrant attention, but occasionally it will cause premature defoliation. In those cases spray once next spring before bud swell.

Link to an INFORMATIVE WEBSITE regarding Oak Leaf Blister placed on the web by Cornell University Plant Disease Diagnostic Clinic

Link to an INFORMATIVE WEBSITE regarding Oak Leaf Blister placed on the web by Plant & Pest Diagnostic Laboratory,Purdue Univesity

Link to an INFORMATIVE WEBSITE regarding Oak Leaf Blister placed on the web by Iowa State University Extension (good photos)

Link to an INFORMATIVE WEBSITE regarding Oak Leaf Blister placed on the web by University of Illinois Extension (good photos)

Sycamore Anthracnose (51)—Sycamore anthracnose, caused by Apiognomia veneta, is starting to cause symptoms on sycamores. Diseased trees are especially conspicuous now as they stand leafless or nearly so next to other tree species with full crowns. Many of the sycamores that we saw while driving along the highway in Westchester looked like they had sycamore anthracnose. They had small, shriveled brown leaves.

    Sycamore anthracnose occurs in three phases corresponding to the plant parts attacked. In order of appearance each season, the phases are canker formation, shoot blight, and leaf blight. Defoliation can occur, but this disease rarely threatens the life of its host and therefore treatments would only need to be made for aesthetic reasons. For new plantings, choose anthracnose-resistant London plane (P.X. acerfolia).

Link to some good photos of Sycamore Anthracnose placed on the web by The Bugwood Network.

Tent Caterpillars (76)—Stephen Harris, Extension Educator from Cooperative Extension of Onondaga County reports the following about tent caterpillars in the Onondaga County area. “I have seen both forest and eastern in the field in the southern part of the county. I have seen forest tent caterpillars in the City of Syracuse but not at the scale reported in phone calls daily from residents in the Tully Valley and Town of Lafayette area. The forest tent caterpillars are now about 1.5 inches long. I have seen them in a variety of settings - on street trees, park trees and trees in high traffic areas. My sightings have been restricted to ornamental cherries and oaks.”Link to an INFORMATIVE WEBSITE regarding Forest Tent Caterpillars placed on the web by Ohio State University

Link to an INFORMATIVE WEBSITE regarding Forest Tent and Eastern Tent Caterpillars placed on the web by Maryland Cooperative Extension

Link to an INFORMATIVE WEBSITE regarding Forest Tent Caterpillars placed on the web by the Canadian Forest Service

Link to an INFORMATIVE WEBSITE regarding Forest Tent Caterpillars placed on the web by the University of Minnesota

Link to an INFORMATIVE WEBSITE regarding Forest Tent Caterpillars placed on the web by the USDA Forest Service

White Prunicola Scale (188)—The white prunicola scales in Long Island and in Westchester and Orange County have laid their eggs. Expect the crawlers to hatch soon. This scale can be found on Japanese flowering cherry, privet, and lilac. The crawlers are salmon colored. This pest causes a white coating on the trunk and twigs of its host plant. Predators and parasites are numerous but are not reliable. Treatments should be made to target the crawlers in mid-June through early July (707-1151 GDD50). (See this week’s Feature Article for more information.)

Scouting Report | Feature Article |Things to Look For | Miscellany | Growing Degree Days |Phenology |

This publication contains pesticide recommendations. Changes in pesticide regulations or human errors are still possible. Some materials may no longer be available, and some may no longer be legal. These recommendations are provided only as a guide.

All pesticides distributed, sold, or applied in New York State must be registered with the Department of Environmental Conservation (DEC). Questions concerning the legality and/or pesticide use in New York State should be directed to the appropriate Cornell Cooperative Extension office or regional DEC office.  Read the label before applying any pesticide. If any information in these recommendations disagrees with the label, the recommendation must be disregarded.

Recommendations for the use of chemicals are included in this publication as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by Cornell Cooperative Extension Service nor discrimination against similar products or services not mentioned. Individuals who use chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage and examine a current product label before applying any chemical.

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