INSECTS NEWSLETTER. Minnesota to Host Ecology of Urban Soils Conference. Plant Phenology and Insect Development

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1 & UNIVERSITY OF ILLINOIS EXTENSION HOME, YARD GARDEN PEST College of Agricultural, Consumer and Environmental Sciences, University of Illinois at Urbana-Champaign Illinois Natural History Survey, Champaign NEWSLETTER No. 3 May 10, 2000 Minnesota to Host Ecology of Urban Soils Conference A national conference, The Ecology of Urban Soils: Designing and Managing Soils for the Living Landscape, will be held June 11-13, 2000, in St. Paul, Minnesota. This conference is for anyone working with the planning, design, construction, and/or maintenance of urban infrastructure and outdoor areas, including engineers, architects, designers, contractors, developers, builders, city planners, arborists, foresters, consultants, scientists, and educators. CEUs are available. Conference information (including speaker abstracts) is posted on APSnet at or contact Cindy Ash for a registration brochure, cash@scisoc.org; (651) Pre-registration payment is due May 10. Give Cindy a call as soon as possible, and tell her you heard about the conference late. She will do what she can to get you registered. This conference is sponsored by the American Phytopathological Society (APS) and cosponsored by a number of horticultural associations, including the American Society of Consulting Arborists and the International Society of Arboriculture. (Bruce Paulsrud) INSECTS Plant Phenology and Insect Development The proper time to control insects can vary depending on the weather. This is most obvious when an early spring, with unusually mild, warm weather, causes insects to be in an advanced stage of development, compared with a late spring, when winter weather persists. The development of plants can be used to predict insect activity. Like insects, the emergence of leaves, flowering, and other phenological events are influenced by the weather. Both plants and insects are likely to be affected by cloud cover, rainfall, and the number of hours at various temperatures. The observation of plant phenology, such as bloom time, can let you know when insect pests are susceptible to control methods. The following is a prediction of the stage of development of several species of insects based on the blooming of bridal wreath spirea or Vanhoutte spirea (Spiraea x vanhouttei). This information is taken from the book Coincide by Donald A. Orton. This 190-page book was published in 1989 and is available from the publisher, Labor of Love Conservatory, 468 S. President, Suite 103, Carol Stream, IL ; (630) This plant phenology information is listed to provide a basis for scouting and identifying potential problems. It helps you know when to look for certain pests. It should not be used as a biological calendar spray schedule. Bridal wreath spirea or Vanhoutte spirea (Spiraea x vanhouttei) Full bloom: Birch leafminer young larvae Elm leaf beetle young larvae European pine sawfly feeding larvae Gypsy moth feeding larvae Pine needle scale crawlers (first generation) Full to late bloom: Lilac (ash) borer newly hatched larvae Oystershell scale (brown) crawlers Finishing bloom: Bronze birch borer newly hatched larvae Most blossoms brown, still a few white: Flat-headed appletree borer larval hatch Peach tree borer newly hatched larvae Viburnum borer newly hatched larvae Bloom finished: Oystershell scale (gray) crawlers (Phil Nixon)

2 2 No. 3 May 10, 2000 Pine Needle Scale In many parts of Illinois, it is time to treat for pine needle scale, Chionaspis pinifoliae. In general, egg hatch occurs when Vanhoutte spirea is in bloom. The young crawlers, which move around on the plant, are much more susceptible to insecticide applications. Mugo, Scots, Austrian, and red pines are susceptible to attack by pine needle scale. Mature pine needle scales are small (2 to 3 millimeters long), elongated white scales that are located on the needles of evergreens. Eggs overwinter underneath the mated adult female scale cover. Females can lay up to 100 eggs. The eggs hatch into crawlers from May through June. The crawlers move about on the plant foliage before finding a place to settle and feed. They suck juices from the mesophyll layer of needles, which causes the needles to turn yellow, then brown. Whole branches may be killed. Heavy scale infestations can kill trees. The young crawlers may be blown onto other plants by wind. There are two generations per year. Management of pine needle scale involves maintaining plant health and using insecticides. Proper implementation of cultural practices, such as irrigation, fertility, and mulching, will minimize stress and allow plants to tolerate low to moderate populations of pine needle scale without suffering injury. The insecticides that can be used to manage pine needle scale include acephate (Orthene), chlorpyrifos (Dursban), diazinon, insecticidal soap, and summer oil. These materials are applied in late May or when Vanhoutte spirea is in bloom. Second generation crawlers can be treated as hills-of-snow hydrangea blooms turn from white to green. Repeat spray applications 7 to 10 days later, as the secondgeneration eggs hatch over a longer period of time. Be careful when using summer oil as it may discolor foliage. (Raymond Cloyd) Oystershell Scale Oystershell scale, Lepidosaphes ulmi, eggs are hatching throughout portions of Illinois. At this stage, the young crawlers are susceptible to insecticide applications. As scales mature, they are more difficult to kill because they form a protective covering. Oystershell scale has a wide range of hosts, which include lilac, birch, dog-wood, ash, elm, poplar, hemlock, walnut, willow, privet, and maple. There are two races of oystershell scale, the brown and gray banded. These two races differ based on their plant preferences. Oystershell scale is small (2 to 3 millimeters long), gray or brown, and shaped like oyster shells. The scale overwinters as eggs underneath the female covering. The eggs hatch into young, creamy-white to brown crawlers, which are active from May through June. Once the crawlers locate a place to settle, they use their piercing sucking mouthparts to remove plant fluids, which causes leaf yellowing, plant stunting, and possible death. Branches or twigs that are encrusted with oystershell scale may die. In some situations, the scale may not kill a tree but stress it enough to increase susceptibility to wood-boring insects. Proper implementation of cultural practices such as irrigation, fertility, and mulching reduces stress and thus allows plants to tolerate low to moderate infestations. However, when scale populations are high, insecticides are generally required to prevent plant damage. Insecticides that are recommended for managing oystershell scale include acephate (Orthene), carbaryl (Sevin), chlorpyrifos (Dursban), malathion, insecticidal soap, and summer oil. These insecticides should be applied when the crawlers are most active. Repeat applications 10 to 12 days later. The brown-race crawlers of oystershell scale on dogwood and lilac are generally sprayed when Vanhoutte spirea is in full to late bloom. The gray-banded race crawlers on ash, lilac, and maple are sprayed when Vanhoutte spirea has completed blooming. The brown race has hatched in southern Illinois but had not yet hatched in central Illinois as of May 2. Hatch in northern Illinois will occur even later. Oystershell scale is susceptible to natural enemies such as parasitoids and predators. However, natural enemies generally appear too late to prevent injury. In addition, natural enemies are usually present only when scale populations are high. (Raymond Cloyd) Bronze Birch Borer This time of year in Illinois, European white birch, gray birch, paper birch, and yellow birch trees growing in landscapes are susceptible to bronze birch borer, Agrilus anxius, infestations. Adult bronze birch borers are coppery-brown with a boat-shaped abdomen. The adult females are strong fliers and lay eggs in cracks, crevices, or under loose bark near the tops of birch trees. Egg-laying sites are generally located on the sunny side of trees. After approximately 2 weeks, eggs hatch into larvae that bore directly into the bark and begin making feeding galleries. These galleries can range from 3 to 5 inches in length and

3 No. 3 May 10, 2000 are packed with excrement. The larvae are ivorycolored, long (up to almost 1-1/2 inches), and flat, with a head that is wider than the body. Larval feeding can result in girdling of the trunk or branches. Infested trees commonly have ridged or swollen bark where larvae have made their zigzag pattern under the bark. Bronze birch borer overwinters as late-instar larvae underneath the tree trunk. Larvae then pupate near the bark surface. They later emerge in late May to early June as adults, by chewing a D-shaped hole in the bark. The adults feed on the leaves of alder, birch, and poplar. There is only one generation per year. The key to managing bronze birch borer is prevention. Bronze birch borers prefer stressed trees because they are unable to survive in healthy trees. Thus, proper watering, fertilizing, mulching, and pruning can reduce the potential for bronze birch borer infestations. The pruning of birches should not be done between May 1 and August 1, as this is the general flight period of the bronze birch borer, and females are attracted to pruning cuts. In addition, planting less susceptible varieties of birch such as Heritage and Whitespire, can lead to fewer problems with bronze birch borer. The insecticide chlorpyrifos (Dursban) or dimethoate (Cygon) are recommended for managing bronze birch borer. These insecticides should be applied to the bark. This will kill larvae that hatch from eggs as well as adults that feed on the bark to provide a site for egg laying. Cygon should be applied to the bark as a band no more than 6 inches wide. (Raymond Cloyd) Flatheaded Appletree Borer Flatheaded appletree borer, Chrysobothris femorata, attacks a wide range of trees and shrubs, especially those in the rose family (Rosaceae), such as cotoneaster, crabapple, hawthorn, pyracantha, and rose. In addition, young maple trees are highly susceptible to borer infestations. Adult beetles attack plants growing in nurseries and landscapes. The adults are 10 to 12 millimeters long with a somewhat flattened appearance. They are metallic and vary in color from brown to gray. Adult females lay eggs in bark crevices. The eggs hatch into legless, creamy-white larvae that bore through the bark into the cambium. The larvae are about 1 inch long when full grown. They produce long, winding, tortuous tunnels in the cambium that can girdle and kill large branches and young trees. Larval activity can usually be detected by the presence of white sap flowing from cracks in the bark. Newly transplanted trees and shrubs are highly susceptible to injury. Eventually, the larvae bore into the heartwood to pupate. The adults that emerge leave a D-shaped hole. There is only one generation per year. Proper irrigation and fertility will promote healthy, vigorous growth and minimize attacks by the flatheaded appletree borer. A horticultural wrap of paper or burlap may be useful in protecting young trees and shrubs. In nurseries, clean cultivation, removing grassy weeds by mowing or using a post-emergent herbicide (i.e., Roundup, Finale, Reward, or Scythe) may reduce potential problems with flat-headed appletree borer. Applications of the insecticide chlorpyrifos (Dursban) or lindane in late May or early June will kill eggs and the newly hatched larvae before they bore into trees. (Raymond Cloyd) Lilac/Ash Borer At this time of year in Illinois, plants such as ash, lilac, and privet are susceptible to attack by the lilac borer, also known as the ash borer. Lilac borer adults are brown, slender clearwing moths that resemble paper wasps. The peak moth flight period occurs in early June. Females lay tan, oval eggs in cracks, crevices, or wounds at the base of plant stems. The females can live up to 1 week and lay 300 to 400 eggs. Eggs hatch into cream-colored larvae with brown heads. The larvae cause plant injury by creating tunnels and feeding within the bark. They bore into the wood and feed within the sapwood and heartwood. Their feeding restricts the flow of water and nutrients, causing shoots to die. The lilac borer generally feeds near the base of plant canes. The larval feeding creates swollen areas or cracks at the base of plants. Evidence of larval feeding is the presence of light-colored sawdust below infected areas. Lilac borer overwinters as late-instar larvae in the tunnels of stems. There is only one generation per year. Prevent plant stress by implementing proper cultural practices such as irrigation, fertility, and mulching, as stressed plants are very susceptible to lilac borer infestations. A 2- to 3-foot-wide mulched area around the base of trees and shrubs will prevent plant injury from lawn mowers and weedwhackers. In addition, avoid pruning plants in late spring and early summer when moths are present. The insecticide chlorpyrifos (Dursban) can be applied to control lilac borer larvae before they enter the plant. Pheromone traps are available that capture adult males, which indicates that females will eventually be 3

4 4 No. 3 May 10, 2000 laying eggs. This can help in timing insecticide applications. Another possible management option is the use of beneficial nematodes. Nematodes are applied as a heavy spray to the larval entry points. The nematodes will attack the larvae feeding within the tunnels. (Raymond Cloyd) Euonymous Webworm Euonymus webworm (also known as Euonymus caterpillar) has been found as young larvae in northeastern Illinois. This insect was present in large numbers last year in this part of the state, particularly on European euonymous. Look for larvae in small webs. The webs increase in size as the larvae feed on the leaves and can become large. The slender caterpillars are a very pale yellow with black spots and can grow up to almost 1 inch long. Bacillus thuringiensis var. kurstaki (Bt) will control young larvae but is less effective on mature larvae. Penetrate the web thoroughly with Bt, as the insect must eat the Bt for it to work. Other insecticides are also effective. (Phil Nixon and The Morton Arboretum) Root Collar Borer The Morton Arboretum has reported a borer in a magnolia, Magnolia officinalis var. biloba, that appears to be root collar borer, Euzophera ostricolorella. This moth borer attacks yellow poplar and occasionally other magnolias. It bores in the inner bark, primarily from 2 inches below to 5 inches above the ground line in situations where the bark is damp. It tends to attack trees that are at least 10 inches in diameter. Heavy infestations can kill the tree. Fullgrown larvae are about 1 inch long. The adult moth is present from May to July. If you notice damage from this insect, please let us know. (Phil Nixon and The Morton Arboretum) PLANT DISEASES Managing Sphaeropsis (Diplodia) Tip Blight and Canker Sphaeropsis tip blight and canker is a disease of Austrian and Scotch pine that has been around for many years in Illinois. The most common symptoms of this disease are blighting of the branch tips and death of lower branches. It tends to be more of a problem in years when we have lengthy, cool, and wet spring weather. Under these conditions, the fungus (Sphaeropsis sapinea) infects immature candle and needle tissues, which is why we see the typical blighting of branch tips. To diagnose the tip-blight phase, collect several brown needle clusters from several shoots that died last spring, then use a hand lens to examine the basal 1/ 2 inch or so of the needles. Look for tiny, black, pinhead-sized fruiting bodies of the fungus. You can often trick the fungus into producing these fruiting bodies by placing diseased shoots in a plastic bag for 24 to 48 hours with a damp paper towel. Keep in mind that these fruiting bodies may not show up in freshly killed shoots. The combination of tip blighting and these fruiting bodies is enough evidence to implicate Sphaeropsis blight. If necessary, laboratory confirmation is quick and easy. For more details about this disease and how to identify it, consult Report on Plant Disease No With the dry weather so far this year across much of the state, experience tells us that it should be a fairly uneventful year in terms of foliar diseases. To some degree, this statement should hold true for Sphaeropsis tip blight and canker. While we may not see as much of the typical new shoot infections as we have in the past few years, a very dry summer may stress the trees to the point where we see more cankering than normal. Research and experience tells us that Sphaeropsis can be quite damaging to trees that are stressed by drought, compacted soils, root injury, and other factors. Under stressful conditions, Sphaeropsis has the ability to invade older branch tissue and cause girdling cankers. As a result, you may see twigs or entire branches dying rather than the typical tip blight. In the last 2 or 3 years, we have seen an increase in Sphaeropsis canker at the clinic. Similar to Cytospora canker on spruce, you should notice at least some white, caked resin associated with Sphaeropsis cankers. This resin can also indicate a wound caused by a variety of insects and animals, so investigate carefully. Researchers consider the fungus Sphaeropsis sapinea to be somewhat of an opportunist. This means the fungus is kind of weak but can easily overcome the defenses of a stressed host plant. Furthermore, we now know that there are two distinct types of the same fungus type A and type B. Type A is more aggressive and is reported to be far more common in Wisconsin and several other states. This all boils down to the fact that we have a complex fungus that can cause disease on healthy new shoots in wet springs and on older tissue during drought conditions. In Illinois, Austrian and Scotch pines are most commonly infected, although almost any stressed conifer should be considered susceptible to infection.

5 No. 3 May 10, 2000 Short-Term Management. As of May 3, many of the Austrian pines in Champaign, Illinois, have new candles that are 2 to 3 inches in length. At this point, you can see the succulent green candle tissue with needles that are just about to break through the papery fascicle sheath. For trees plagued by Sphaeropsis from previous years, making the first fungicide application of the year at this point would be ideal, particularly since we ve had some rain already and the forecast calls for a bit more. Warmer weather to the south and in other parts of the state has certainly pushed growth along much further. For those who have already made the first or second application, you may be wondering if a second or third application is needed. The answer largely depends on the weather in your area. Keep in mind that the fungus is most damaging to new shoots under moist conditions and that new candles and needles are most susceptible during a 3-week period following bud break. Reports from researchers and practitioners in Illinois and neighboring states indicate that thiophanate-methyl (active ingredient) is an effective systemic fungicide and that chlorothalonil is acceptable as a contact-type fungicide. Registered fungicide options are listed in the Illinois Commercial Landscape and Turfgrass Pest Management Handbook Homeowners can check the listings in the Illinois Homeowner s Guide to Pest Management. Long-Term Management. There is no research to support the use of a fungicide beyond springtime to protect a stressed tree from Sphaeropsis cankers. Similarly, we don t recommend any sprays to manage Cytospora canker of spruce. Your best option is to do what you can to reduce the local inoculum (spores) and prevent excessive stress on the tree. Diseased branches, branch tips, and cones all contribute to future infections. Prune diseased branches 6 to 8 inches below the point where they are obviously infected. This is best done in the dormant season but can be done at other times when the foliage is dry. Dip your shears in a 10% bleach or 70% ethanol solution between cuts to reduce the chances of infecting healthy tissue. Cones are the next target for control. Take a close look at some fallen cones or older cones still attached to the tree, and you ll probably find that they are loaded with the same fruiting bodies described above; this is a major source of spores for new infections. Pick up the fallen cones and, where practical, remove them from the tree. Doris Taylor of The Morton Arboretum recently provided some advice about establishing effective watering habits ( Drought Stress, The Plant Health Care Report: The Morton Arboretum, April 1-7, 2000, Issue ). This, and the above advice, should go a long way toward reducing disease potential and eventually improving the look of your pines: Because root systems of established plants are wide spreading and deep, it is vital that enough moisture be applied to reach them. Established trees and shrubs should be watered deeply every 10 to 14 days during dry periods. Irrigate slowly so water percolates down into the soil. Know your soil. Observe how quickly soil dries out after a rain or watering. During late fall, water trees and shrubs well, especially evergreens, when soil moisture is low. Mulch plants with a 3- to 4-inch layer of organic mulch (wood chips, shredded bark) to reduce soil evaporation and temperature fluctuations and to conserve moisture. Do not fertilize unless adequate irrigation is available. (Bruce E. Paulsrud) Leaf Diseases of Deciduous Trees Early-season leaf diseases of trees often cause undue concern and alarm for homeowners. Master Gardeners and landscape maintenance personnel also often become very adamant about making exact fungal identifications. It is good to know that many are being very careful about making a proper diagnosis. Still, when it comes to spring and leaf spotting diseases of deciduous trees, don t lose too much sleep worrying about an exact fungal identification. You might see Septoria on magnolia; Phyllosticta on maple; Cercospora on sweetgum; an anthracnose on sycamore, ash, oak, or maple; or a myriad of other fungi on other tree hosts. Most of these diseases will be treated the same. Will we see these leaf diseases in 2000? Most of these fungi infect succulent new growth because the leaf cuticle is still developing and the leaf is tender. Early-season infection generally requires cool and wet conditions as the leaves are emerging. Because Illinois average temperatures have been much warmer than usual this year, and the weather has been much drier than usual, we don t expect to see major problems with leaf diseases. Keep in mind, however, that we have had many showers, and if these showers coincide with cool temperatures and leaf emergence, the fungal leaf diseases will result. In fact, anthracnose has been seen on sycamore; and a case or two of maple anthracnose has been reported to the Plant Clinic this year. 5

6 6 No. 3 May 10, 2000 Anthracnose is the most common group of deciduous tree leaf diseases. Although the term anthracnose causes most people to think of one disease, it is actually a term used to refer to diseases caused by fungi that produce fruiting structures called acervuli. This is of significance to laboratory diagnosticians but is not of much value in the field. The anthracnose diseases of trees may cause leaf spotting alone (ash and maple anthracnose), stem cankers (oak anthracnose), or a combination of both (sycamore anthracnose). The causal pathogens are fungi including species of Discula, Discella, Gloeosporium, Monostichella, Kabatiella, and others. In terms of disease management, it is not necessary to know the exact fungus-producing symptoms. Probably the most dramatic leaf spotting and leaf drop we see in Illinois from anthracnose is on ash, sycamore, and walnut. A tremendous amount of leaves with brown to black spots and blotches may fall from the tree. With warmer weather and rain, the trees will produce a new flush of leaves and will recover. There are few fungicide applications recommended on landscape plants that will work as rescue treatments. In most cases the use of fungicides in the landscape serves as a protective barrier against infection, not a cure of an existing infection. Although we may not be able to provide immediate remedy for disease infection, we have time to assess the severity of an infection, follow up on accurate diagnoses, initiate cultural management procedures, and then to use a fungicide the following year if needed. In most cases we do not recommend the use of fungicides for anthracnose disease management on trees. Instead, improve tree vitality by watering in periods of drought, fertilizing in the fall, and removing dead wood. For further information, consult Reports on Plant Disease (RPDs) No. 648, Leaf Spot Diseases of Shade and Ornamental Trees in the Midwest; No. 621, Anthacnose Diseases of Shade Trees; or several other reports discussing leaf spots on specific hosts: RPDs 600 (Black Walnut), 601 (Mountain-Laurel), 637 (Hawthorn), and 638 (Firethorn). These are all available in Extension offices. RPDs 601 and 621 are also available on the Web at pubs.html under horticulture publications. (Nancy Pataky) Disease Sightings The list of diseases reported and confirmed so far this year shows the extremes in weather patterns within the state. Cedar-apple rust galls on cedars have been active for several weeks, a condition requiring moisture. Anthracnose on sycamore and bacterial blight on lilac have also been seen both requiring moist, mild conditions. On the other hand, powdery mildew has been common on turf, and it requires cool, dry conditions. The reason we will continue to see all types of diseases is that the textbook conditions are usually those needed for infection. That process can occur in a few hours or a few days. Don t let the overall dry pattern lull you into disease complacency. Other diseases confirmed at the Plant Clinic include Verticillium on magnolia, Dutch elm disease, and Cytospora canker on Douglas fir. (Nancy Pataky) Home, Yard, and Garden Pest Newsletter is prepared by Extension specialists from the University of Illinois at Urbana-Champaign and the Illinois Natural History Survey. Information for this newsletter is gathered with the help of staff members, Extension field staff, and others. Karel Jacobs and Donna Danielson of The Morton Arboretum also provide information and articles. Major authors are Phil Nixon, (217) , Fredric Miller, (708) , and Raymond Cloyd, (217) , entomologists; Nancy Pataky, plant pathologist, (217) ; Bruce Paulsrud, pesticide applicator training, (217) ; and Tom Voigt and David Williams, horticulturists, (217) Phil Nixon is the executive editor of the Home, Yard, and Garden Pest Newsletter. This newsletter is written by faculty in the Department of Natural Resources and Environmental Sciences and the Department of Crop Sciences. The newsletter is edited by Erin Cler, typeset by Oneda VanDyke, and proofread by Phyllis Picklesimer, all of Information Technology and Communication Services. For subscription information, phone (217) or (800) , or acesnews@uiuc.edu. Web subscriptions are available ( cespubs/hyg).

7 NEWSLETTER SERVICE UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN 528 BEVIER HALL, MC S. GOODWIN AVENUE Return Service Requested University of Illinois U.S. Department of Agriculture Local Extension Councils Cooperating Univeristy of Illinois Extension provides equal opportunities in programs and employment. Presorted First Class U.S. Postage Paid Permit #75 Champaign, IL No. 3 May 10, URBANA, IL U OF I EXTENSION