UNIVERSITY OF ILLINOIS EXTENSION HOME, YARD ARDEN PEST College of Agricultural, Consumer and Environmental Sciences, University ofG Illinois at Urbana-Champaign &Illinois Natural History Survey, Champaign NEWSLETTER

No. 2 • April 20, 2005

cankers. Copper compounds are usually applied PLANT DISEASES before green tip (when the tips of green leaves begin Watch for Fire Blight to emerge from buds). Copper products may include Fire blight is a bacterial disease that causes concern Camelot, Champion, Chipco Aliette, Junction, Kocide, to growers with apples, pears, crabapples, and orna- Magellan, Nu-Cop, Phyton 27, and others. Antibiot- mental Callery pears. You might also see infection on ics are used in commercial fruit-production areas to other rosaceous hosts, such as cotoneaster, hawthorn, prevent fi re blight. Sprays are made during bloom, quince, fi rethorn, and mountain-ash. Fire blight is specifi cally when no more than 10% of the blooms are caused by a bacterium (Erwinia amylovora), and the open on the tree. There are few antibiotics available or bulk of the infection occurs during fl owering when recommended for ornamental plants. It is best to rely temperatures are warm (mean daily temperature of at on nonchemical management practices to control fi re least 60°F) and conditions are wet. The causal bac- blight on ornamental plants. terium may spread by wind, water, equipment, and A few other helpful management tips include avoid- animals. Rain or insects may move the bacterium from ing high-nitrogen fertilizers that promote lush suscep- cankers and bark to open blossoms, vigorous shoot tible growth, removing water sprouts when they are tips, and leaves. As long as warm, wet conditions small, and removing nearby neglected pear and apple continue during bloom, the bacterium can continue trees. (Nancy Pataky) to infect. Management practices focus on controlling the bacterium during fl owering. The bacterium is also Steps in Diagnosing a Plant Problem known to cause infection directly through wounds Many of you feel very comfortable trying to diagnose made during a hailstorm. a plant problem, readily separating the noninfectious Look for water-soaked or wilted new growth that from the infectious causes or quickly distinguishing quickly turns brown to black and remains attached to insect injury or site stress. Still, I know from telephone the stem. Also, dark cankers may develop in the wood, inquiries that others are uncomfortable making such especially on edible and ornamental (Callery) pears. diagnoses and have requested some help. Here are Because the bacterium originates on old cankers some step-by-step suggestions on how to go about and bark infection, removal of branches killed by fi re diagnosing a plant problem. blight is extremely helpful in disease control. This Above all else, do not let anyone rush you into a di- should be done when the tree is dormant or after the agnosis. “On-the spot” diagnoses and partial informa- infection, when weather is hot and dry. Disinfecting tion are the most direct route to a misdiagnosis! This pruning equipment is an important step is reducing may cause unnecessary expense, concern, and delay in disease spread. Use 10% household bleach or similar getting to the actual cause of the problem. disinfectant between cuts. Step 1. Identify the plant species. In fact, knowing If you are thinking of planting new trees, do a bit of the cultivar or hybrid may also come in handy. If you searching for resistant varieties. It will be well worth know the host, you can eliminate many problems that your search. Among the ornamental Callery pears, wonʼt occur on that host, and you can start looking in ʻAristocratʼ and ʻAutumn Blazeʼ have good resistance reference books, on Web sites, or in fi les for problems reports. Also refer to the University of Illinois Report that might occur on that host. For instance, sudden on Plant Disease on fi re blight at http://www.ag.uiuc. stem tip necrosis and death on crabapples could be the edu/~vista/horticul.htm. result of fi re blight infection, but that disease will not Pesticides may be used for fi re blight prevention. occur on redbud. A dormant (early-season) application of copper may Step 2. Determine what is wrong. This may seem be of some benefi t to kill bacteria as it oozes from obvious, but sometimes drooping foliage, variegated 2 No. 2 • April 20, 2005 leaves, or bark splitting is normal for a species. Some- often associated with site stress, so donʼt be too quick times the yellowing of leaves is a problem, while to blame only this disease. We have seen cases where other times it is a cultivar quality. spider mites, root rot, and even weed trimmer injury of Step 3. Dig out the facts. This is probably the the trunk were the major problem, but Rhizosphaera most important part of the diagnostic process. Details was present and was the only problem addressed. on symptom expression are much more useful that There may be more than one problem on a plant. Rhi- generalizations such as “my plant is dying.” The pres- zosphaera often accompanies other problems. ence of fruiting bodies, mushrooms, conks, bacterial The disease is Rhizosphaera needle cast; and the ooze, insects, insect parts, insect trails, odd growth, cause is a fungus, Rhizosphaera kalkhoffi i. Blue or information on anything abnormal can help the spruce is most often infected, while Norway spruces diag nosis. Critical information includes a description are resistant. Infection is favored by wet weather, but of the pattern of the problem over the entire planting symptoms do not often show for 12 to 18 months after and a description of the pattern of the problem on one initial infection. Rhizosphaera needle cast may cause affected plant. For instance, the problem might occur severe defoliation of spruce, a species that does not only along one side of the property and only on one refoliate readily. A few years of infection may cause a side of all plant species. Such a description would very unsightly and weakened spruce. Fungicides are strongly suggest a wind or weather stress or possibly often recommended for control, but such fungicides a chemical drift. As another example, only a few of are preventives, meaning that you apply the fungicide the pines are affected, and they have suddenly turned before new infection occurs in a given year. The usual brown over the entire tree. This might involve a root series of events is the positive identifi cation of Rhizos- problem or possibly pine wilt. Finally, it is helpful to phaera in year 1, followed by use of a fungicide in the know how things have changed on the site just before spring of year 2. It may be necessary to use cultural the problem was manifested. Often this information controls, as well as fungicide sprays, for several suc- leads us to investigate cultural problems, construction cessive years until the disease is under control. Two injury, weather stress, or the like. sprays are recommended for control of this fungus–one Investigate conditions around the plants, weather, when the bud caps have fallen off and another about chemicals, and any other facts that might have a bear- 2 or 3 weeks later. Chemical options for commercial ing on symptom development. growers include Camelot, Chlorostar, Daconil, Echo, Step 4. Consult references. There are textbooks Kocide, Manicure, Protect T/O, Spectro, and Two- that list problems by host; books on insect problems, Some. Home growers can choose a labeled chloro- diseases, chemical injury, nutritional problems, and thalonil product, such as Dragon Daconil or Ortho the like. There are university fact sheets, Web sites, Daconil. Tables at the end of disease chapters in the and advice from specialists. Start with a general plant pest management handbooks list the active ingredient problem reference that lists many problems for each and mobility of chemicals mentioned. Company names host. Extension offi ces have many useful references to are also listed. Pick a product that works best for you, get you started. but read and follow label directions carefully. Refer to Step 5. Determine probable cause(s). At this the Home, Yard, and Garden Pest Guide or the 2005 point, you might want to ask for diagnostic help if you Commercial Landscape and Turfgrass Pest Manage- are uncertain. There is always the University of Illi- ment Handbook. nois Plant Clinic! Check out the Plant Clinic services Remember, there are many other noninfectious at http://plantclinic.cropsci.uiuc.edu/. Most Illinois problems that can mimic this disease. A few possi- Extension unit offi ces also have Master Gardeners bilities include an imbalance in soil pH, poor fertil- who have been trained to help in plant problem diag- ity, fertilizer or chemical burn, root injury, root rot, nosis. The Master Gardener Web site is http://www. drought stress, and spider mite infestations. To confi rm extension.uiuc.edu/mg/. (Nancy Pataky) the presence of the pathogen, look for fruiting bod- ies (pyc ni dia) on the discolored needles. It might be Rhizosphaera Needle Cast of Spruce necessary to place some affected needles in a moisture Rhizosphaera needle cast of spruce is seen frequently chamber (plastic bag with moist toweling) overnight to in Illinois. This fungal disease causes one-year-old encourage growth of fruiting bodies. Look for pin- needles to turn purplish brown before they drop. The head-sized black structures poking out of the needle newest growth remains green and healthy. The pattern through stomates. A hand lens is usually required to on the tree is usually scattered hot spots, giving areas observe these structures, which occur in rows. They of thinned foliage scattered in the tree. The disease is do not easily rub off because they are embedded in No. 2 • April 20, 2005 3 the tissue. They are about the size of the head of a pin. when it comes time to treat actively growing nim- A good image of these fruiting bodies can be seen at blewill, extend spray coverage beyond the immediate http://www.extension.iastate.edu/Pages/plantpath/clinic/ patches, as creeping stems are prone to lurk in these Rhizosphaera%20close.jpg. If your are uncertain of areas. Stolons missed by applications may form sub- your diagnosis, consult a university Extension offi ce or sequent patches. the Plant Clinic. (Nancy Pataky) Many of our cool-season turfgrasses are dormant during hot summer days. Meanwhile, nimblewill is actively growing and enjoying the lack of competi- WEEDS tion. This unbalance can allow nimblewill to be a Nimblewill Now Easily Noticed serious weed problem. Therefore, controlling patches Itʼs fi nally spring, and our cool-season turfgrass lawns while they are smaller is recommended. For up-to- are rapidly greening up. However, there may be a date lawn weed-control recommendations, consult grassy weed living in your lawn that is much slower to with the University of Illinois Extension publication, awake from its winter rest. Nimblewill (Muhlenbergia Illinois Commercial Landscape & Turfgrass Pest schreberi) is most obvious this time of year. While dor- Management Handbook, as well as the Home Yard mant, its appearance is that of very light tan-colored, and Garden Pest Guide. (Michelle Wiesbrook and “puffed up” patches (the patches look like buff-colored Tom Voigt) scouring pads). When nimblewill greens up to a grayish or bluish green in late spring, its appearance is more inconspicuous. It tends to go dormant fairly early in the INSECTS fall as well and therefore may be noticed then, too. Scouting Watch Nimblewill is a warm-season perennial grass that This newsletter issue brings another phenology plant is fairly common in Illinois. Typically found grow- event: The redbuds are in bloom in central and south- ing in shady or wet lawns and landscapes, it creeps ern Illinois and will soon be blooming in northern by aboveground, horizontal stems that can root at the Illinois. nodes and readily form patches. Its leaves are smooth, Zimmerman pine moth is susceptible to applica- quite narrow, and short compared to many grass tions of permethrin in northern Illinois and may still species. Individual plants look almost wiry. In fact, be susceptible to treatment in central and southern Il- another name for this grass is wire-grass. A closer look linois. Zimmerman pine moth hatches in late summer at this plant reveals a very short, membranous, toothed into a small caterpillar that roams across and feeds a ligule. The leaves are rolled in the bud. The fl ower is a little on bark before fi nding a loose piece of bark to fi ne, slender panicle. crawl under. There, the young caterpillar spins a thin In Illinois, nimblewill may be confused with zoy- silk case over itself, a hibernaculum, and stays there siagrass, which has a similar growth pattern. However, until spring. At this time of year, the larva leaves the dormant zoysiagrass is more of a golden tan in color, hibernaculum and crawls across the bark of the tree and unless planted it is very unlikely to suddenly ap- for a few days until it locates a place to tunnel under pear as a weed. the bark. During each of these wandering times by the Although easy to identify this time of year, nim- small caterpillar, late summer and early spring, it is blewill is best controlled in the summer, when it is susceptible to insecticidal control. actively growing. Proper cultural practices can sig- Gypsy moth eggs will be hatching in northern nifi cantly aid in controlling lawn weeds. Be sure that Illinois in about 2 weeks and will be susceptible to watering, fertilizing, and cultivating are done properly Bacillus thuringiensis kurstaki and other insecticides. and at the right time. However, it is best to wait until the oak trees have Many lawn weeds can be controlled with herbi- leafed out enough to provide suffi cient surface for the cides. Unfortunately, there are no selective herbicides insecticide to land upon. This is normally about mid- available for the control of nimblewill. Nonselective May in northern Illinois. herbicides such as glyphosate can be used, but keep Japanese beetle insecticide applications should be in mind that nontarget desirable plants such as blue- made by the end of April if you are using imidacloprid grass may be seriously injured or killed if contacted (Merit) as a soil application. It takes 2 months for imi- by glyphosate. Also, to be effective, glyphosate should dacloprid to circulate up through the plant so that it is be sprayed on green, actively growing plants. Because in the leaves when Japanese beetle adults start to feed nimblewill patches are obvious now, make a note of in late June to early July. Realize that imidacloprid ap- where they are located. Later in the growing season, plied this way is effective on most trees and shrubs, but 4 No. 2 • April 20, 2005 that there will be an occasional plant where the beetles Eastern and Cooley Spruce Gall Adelgid will feed regardless of the treatment. (Phil Nixon) Galls, in general, are not harmful to trees and shrubs. In fact, they can make plants look more attractive (in European Pine Sawfl y my opinion). However, there are several galls or gall- This is the time of year when the eggs of European makers that occur in Illinois that are not only an aes- pine sawfl y, Neodiprion sertifer, hatch into larvae thetic concern but also may have an economic impact (NOT CATERPILLARS) that are 1/4 inch long, olive on trees and shrubs. These include the horned oak gall green, with a distinct black head capsule. Older larvae (Callirhytis cornigera) and gouty oak gall (Callirhytis are at least 1 inch long, with green stripes. The larvae quercuspunctata), which are caused by cynipid wasps, of European pine sawfl y are gregarious—tending to and Cooley spruce gall adelgid (Adelges cooleyi) and feed in large groups. When disturbed, the larvae en eastern spruce gall adelgid (Adelges abietus). These masse arch back on their hind legs, almost forming an last two galls are caused by adelgids, which are insects “S” shape. This behavior is a defensive response to that resemble aphids—except they donʼt possess the avoid predation—primarily by birds. The larvae feed cornicles (tailpipes). on the needles of a wide range of pines; however, they Cooley spruce gall adelgid has a complex devel- tend to prefer Scotch, red, and mugo pine. Larvae strip opment sequence that utilizes alternate hosts to com- the needles of mature foliage, leaving only a central plete its life cycle. In some situations, this adelgid can core, which appears white and then turns brown. continue to infest one host without the other host being Any damaged needles eventually fall off. The larvae nearby. It typically takes 2 years to complete develop- have normally completed feeding by the time needles ment on Douglas fi r and spruce. Galls are formed on emerge from the candelabra. As a result, newly emerg- spruce—not on Douglas fi r. Cooley spruce gall adelgid ing needles are not fed upon. In general, European pine causes spruce trees to form conelike structures on the sawfl y is not a major concern because there is minimal tips of new growth. Susceptible hosts include Colorado threat of branch or tree death due to feeding—unless blue, Sitka, oriental, and Engelmann spruce. The galls the tree is very young (1 year old or younger) and a are green to purple, 1 to 2 inches long, and resemble large population of larvae is feeding. Additionally, small pineapples (think Hawaii). These galls eventu- the loss of second- and third-year needles may be a ally turn brown. Adelgid feeding may also cause concern, as this injury can ruin the aesthetic appearance needle distortion and yellowing. of landscape and Christmas trees. Later in the spring, Winged adults migrate from Douglas fi r to spruce the larvae fall to the ground and pupate inside brown, around July. On the terminal growth, female adelgids leathery cocoons around the base of trees. The adults lay eggs that hatch into nymphs, which overwinter on resemble wasps, and emerge in the fall; the females spruce trees. Prior to budbreak in spring, the nymphs deposit eggs in the needles prior to winter. Females become active. They eventually develop into adult create yellowish scars or wounds in the needles with females, with each female capable of depositing over their ovipositor when laying eggs. In Illinois, there is 100 eggs on the terminal growth of spruce. The eggs one generation per year. hatch into nymphs that crawl to the base of needles A very quick (and environmentally friendly) way and feed. As the adelgids feed, they inject saliva that to deal with an infestation of European pine sawfl ies contains compounds that cause spruce trees to produce is either by hand removal (if feasible) or by washing a succulent, cell-like compartment, or gall, about 2 to the larvae off plants with a hard stream of water (this 3 inches long, which surrounds each individual adel- doesnʼt include the use of a fi re hose). If warranted, a gid. During summer, the galls formed on the tips of number of insecticides may be applied to infested trees, twigs on spruce become woody and open, releasing including acephate (Orthene), azadirachtin (Ornazin/ winged adults that migrate to Douglas fi r, where the Azatin), carbaryl (Sevin), or spinosad (Conserve). females deposit eggs—producing another generation Although European pine sawfl y larvae resemble of adelgids. Sometimes Douglas fi r may be so heavily caterpillars (Order: Lepidoptera), they are actually lar- infested that the needles appear to be sprinkled with vae of insects closely related to wasps (Order: Hyme- snow. These eggs hatch into nymphs that overwinter noptera). So what does this mean? Well, it means that on Douglas fi r. Again, no gall is formed on Douglas fi r. the bacterial-based insecticide Bacillus thuringiensis Just before budbreak, the nymphs become active var. kurstaki (Dipel or Thuricide), which is recom- and initiate feeding, which causes needle distortion or mended for control of young caterpillars, does not yellowing. These nymphs develop into adults during control European pine sawfl y. (Raymond A. Cloyd) spring and then produce offspring in the summer that No. 2 • April 20, 2005 5 may be either winged or wingless. Wingless adults gall adelgid. Be sure to apply sprays to trees just remain on Douglas fi r, whereas winged adults migrate before budbreak to kill the nymphs that hatch from to spruce to complete the life cycle. Two or more par- the cottony egg masses located at the base of needles. thenogenetic (without mating) generations may occur (Raymond A. Cloyd) each year on the needles of Douglas fi r. Management of Cooley spruce gall adelgid involves Spruce Spider Mite dealing with the insect on both spruce and Douglas fi r Spruce spider mite and its relatives such as pine mite trees. Insecticides recommended for control include and juniper mite, are susceptible to control by miti- carbaryl (Sevin), imidacloprid (Merit), insecticidal cides at this time of year. Damaged spruce foliage will soap, or a summer (horticultural) oil. For spruce, ap- appear bronze in color from a distance. When inspect- ply sprays in spring just before budbreak to kill the ing it closely with a hand lens, you will see that the fo- nymphs overwintering on trees as eggs. This also pre- liage is covered with tiny brown spots where the mites vents adult females from laying eggs on young nee- have fed. These brown spots, surrounded by the green dles. It should be noted that removing galls by pruning color of the needles, gives the foliage the bronzed would not control the problem. For Douglas fi r, apply appearance. Pine needles damaged by pine mite and recommended insecticides such as insecticidal soap juniper foliage damaged by juniper mite may be light or summer (horticultural) oil to control nymphs and green or whitish rather than bronze. On close inspec- prevent further infestations. When installing a new tion, this will be caused by white spots where the mites landscape, it is best to avoid interplanting spruce with have fed. Foliage attacked by any of these three mites Douglas fi r. may be brown. These mites can kill the plants if dam- Eastern spruce gall adelgid attacks Norway, age is severe. white, and black spruce. Feeding by eastern spruce Scout for the mites by holding a piece of white gall adelgid causes spruce trees to form pineapple- paper below a branch and then striking the branch shaped galls (again, think Hawaii) that are 1/2 to 1-1/2 sharply. This will knock many of the mites off the inch in length, at the base of new growth. Adelgid foliage onto the paper, where they can be easily seen. feeding also distorts shoot growth. Galls that are pro- Spruce spider mite and its relatives are tiny, relatively duced in midsummer open and release adelgids. How- slow-moving, and greenish to gray, with eight legs. ever, unlike Cooley spruce gall adelgid, these remain When smashed, they streak green across the paper. on the spruce. Eastern spruce gall adelgid overwinters There may also be some other mites that are red and as an immature female in cracks and crevices at the much faster-moving than the spider mites. They streak base of buds. In spring, prior to budbreak, adelgids red when squashed. These red mites are likely to be mature into adults, and each female deposits 100 to predatory mites that are feeding on the spider mites. 200 eggs under a mass of cottony wax. Eggs hatch, in If they are common, treatment probably is not needed general, when buds open in the spring and when new because they will control the spider mites for you. needles are exposed. Spider mites are most susceptible to control when Feeding by the nymphs on new needles and then they are actively feeding. Sprays of bifenthrin (Tal- on the base produces abnormal twig growth and then star), insecticidal soap, and summer spray oil should galls, which develop at the base of the shoots. The be effective at this time. Christmas tree growers and galls contain many cells fi lled with immature adel- nurseries can also use dimethoate (Cygon). Repeat the gids, which are protected from natural enemies and spray one week later. Realize that spray oil removes environmental conditions. These galls detract from the the blue bloom from Colorado blue spruce and juni- aesthetics and symmetry of spruce trees. Additionally, pers, making them green. Depending on the weather, if galls are abundant in large numbers, this can de- these spider mites lay over-summering eggs in late crease tree vitality or weaken it to the point of increas- April in southern Illinois, mid-May in central Illinois, ing susceptibility to wood-boring insects. or late May in northern Illinois. After these times, The galls eventually open in summer, and mature these miticides will not be effective on these mites nymphs crawl out. Nymphs settle on the needles and until fall when the eggs hatch. (Phil Nixon) then change or transform into winged, egg-laying females. The females generally deposit eggs near the Juniper Webworm tips of needles. Eggs hatch into young nymphs that Juniper webworm spins webs across the foliage of congregate on terminal growth, where they overwinter. juniper and feeds upon it, turning the foliage brown. Insecticides recommended for control of Cooley Generally, damage is more severe in northern Illinois spruce gall adelgid may also be used for eastern spruce than in the rest of the state although the pest can be 6 No. 2 • April 20, 2005 found farther south. Severe damage causes all the fo- chinch bugs, webworms, cutworms, and other insect liage to turn brown, and loss of the plant can result. pests of turfgrass. Arena works through contact and Moths emerge to lay eggs at or near shoot axils ingestion. In addition, it has systemic activity and has in June in central Illinois and early July in northern the same mode of action as imidacloprid (Merit). Both Illinois. The young larvae feed within the needles as Arena and Merit act on the central nervous system, leafminers, with each larva mining several needles. causing irreversible blockage of the postsynaptic nico- Later in the season, they emerge from the needles to tinergic acetylcholine receptors. This means that Arena feed on the surface of needles, spinning silk around and Merit should not be applied in succession, to re- their feeding areas. Typically, about three caterpil- duce the likelihood of resistance. (Raymond A. Cloyd) lars are present in each mass of silk webbing. The caterpillars are slender, with dark brown stripes and a tan to medium brown body. They are about 1/2 inch Home, Yard, and Garden Pest Newsletter is prepared by Exten- long when fully grown. They overwinter in these silk sion specialists from the University of Illinois at Urbana-Cham- masses, emerging to feed again in the spring. Most of paign and the Illinois Natural History Survey. Information for this newsletter is gathered with the help of staff members, Extension the webbing and heavy feeding occurs in the spring fi eld staff, and others. Karel Jacobs and Donna Danielson of The before they pupate. Morton Arboretum also provide information and articles. Control the caterpillars at this time with sprays of Major authors are Phil Nixon, (217)333-6650, Fredric Miller, acephate (Orthene), Bacillus thuringiensis kurstaki (708)352-0109, and Raymond Cloyd, (217)244-7218, entomolo- (Dipel, Thuricide), carbaryl (Sevin), or spinosad gists; Nancy Pataky, (217)333-0519, plant pathologist; Bruce Paulsrud, (217)244-9646, pesticide applicator training; and (Conserve). Use heavy pressure to force the insecti- Tom Voigt and David Williams, (217)333-0350, and Michelle cide into the interior foliage of the plant where many Weisbrook, (217)244-4397, horticulturists. Phil Nixon is the of the caterpillars are located and to penetrate the executive editor of the Home, Yard, and Garden Pest Newsletter. protective silk webbing. (Phil Nixon) This newsletter is written by faculty in the Department of Natural Resources and Environmental Sciences and the Department of Crop Sciences. It is edited by Mary Overmier and typeset by Arena: A New Insecticide for Turfgrass Pests Virginia Cuppernell, Information Technology and Communication Arena, an insecticide from Arvesta Corporation (San Services. Francisco, CA), has received federal registration. The For subscription information, phone (217)333-2666 or (800)345-6087, or e-mail [email protected]. Web subscriptions active ingredient is clothianidin. Arena is formulated are available (http://www.ag.uiuc.edu/cespubs/hyg). as a 0.5% granule and a 50% water-dispersible gran- ule. This insecticide is labeled for control of grubs, Copyright © 2005, Board of Trustees, University of Illinois