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| Landscape Alert newsletter | |||||||
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| Vol. 23, No. 13, July 11, 2008 |
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| In this issue Landscape and nursery Friendly fungus expected to slow down gypsy moth European chafer grubs in nursery fields Poplar and willow borer damaging pussy willows in nurseries Nursery growers bus tour to visit Ohio nurseries Deer Resistant Plants for Homeowners (E-3042) now available Verticillium wilt refresherTurfgrass July is the best time to treat home lawns and golf courses for European chafer and Japanese beetle Japanese beetle biocontrol field day at Willow MetroparkChristmas trees and forestry Balsam fir sawfly Gypsy moth spray window updateAround the home Glyphosate injury on tomato Fallen oak branches signal the work of the twig pruner Big ol’ hairy spiders Larder beetlesOther news Weather news
Next issue July 25 |
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| Friendly fungus expected to slow down gypsy moth |
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| The outbreaks of gypsy moth that we are seeing around the state at this time may be due to two or three relatively dry springs in a row. Entomophaga cannot sporulate and infect caterpillars under dry weather conditions. However, the wet spring and early summer that we have had so far this year has allowed Entomophaga to spread quickly. Take a look at the oak, birch, poplar or other infested trees on your property. You may find many dead caterpillars (mushrooms) on the trunks. If Entomophaga is active in your area, the gypsy moth population will naturally decline, so you may not see nearly as many caterpillars next year or the year after. View PowerPoint presentation about gypsy moth and Entomophaga in Michigan. |
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| European chafer grubs in nursery fields European chafer continues to spread and occasionally cause damage to spruce, arborvitae and other field-grown nursery plants including some perennials. Discus or Flagship applied in July is very effective for preventing grub problems. Granular formulations remain stable until it rains. Sprayable formulations must be watered-in or covered with soil. Discus applications made in July for European chafer should also help reduce problems with soft scale insects and spruce gall adelgids next spring. |
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| Poplar and willow borer damaging pussy willows in nurseries |
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| Nursery growers bus tour to visit Ohio nurseries MSU Extension Horticulture and Marketing Educator Thomas Dudek is planning to take a bus-load of Michigan nursery growers on a two-day trip to visit five nurseries in Lorain and Lake County, Ohio August 19 - 20. |
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| Deer Resistant Plants for Homeowners (E-3042) now available A new publication is now available free of charge from the MSU Extension Publications office titled: "Deer Resistant Plants for Homeowners." This publication provides tables that are a guide to selecting ornamental plants that are less likely to be damaged by deer. It also lists those that are more frequently require protection to prevent damage. "Though no plants are totally resistant to deer browsing, some are less palatable to deer and are less likely to receive heavy damage" according to Jordan Pusateri Burroughs, Department of Fisheries and Wildlife at MSU who co-authored the publication. To obtain a copy go to: http://www.ipm.msu.edu/cat08land/pdf/7-11deerresistant.pdf or contact your local MSU Extension office. |
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| Verticillium wilt refresher
Reprinted with permission from Branching Out, An IPM Newsletter for Trees and Shrubs, Vol 14, No.7 http://branchingout.cornell.edu/. This article was originally printed in the July 13, 2007 issue of the Landscape Alert. Symptoms of verticillium wilt can be confusing because they are so variable. They include marginal scorch and complete wilting of leaves on individual branches in the crowns of potential hosts. Symptoms can occur at any time of the year but often show up when hot, dry weather begins. Sometimes a single branch or the foliage on one side of a tree will die. Trees can go through years where no symptoms are present and then the symptoms show up again several years later. Some trees can struggle along for years, while others may die soon after symptoms appear. In addition to wilting, other symptoms may include: small leaves, stunting shoot growth, poor radial growth, sparse foliage and abnormally large seed crops. (view photos below) There are many other factors that can cause leaf wilt and branch dieback. In general, adverse site conditions and environmental stress such as girdling root injury, drought, flooding, compaction, deicing salts or gas leaks can cause symptoms similar to verticillium. In addition, canker-causing fungi that grow through the bark and cambium to almost girdle a branch can cause wilting. Bark beetles, wood boring insects or sapsuckers can attack selected branches in a tree and cause enough girdling to result in branch failure as well. The question of whether the cause is verticillium or something else is best answered by having the sample tested. Vascular streaking One reasonably reliable diagnostic feature is that sapwood plugged by verticillium may be stained green (in maples) or brown (in other species). However, this discoloration is not always easy to find because it may occur up to several feet below the point where leaves are actually wilting. If you suspect verticillium, begin looking for the stain in the outer sapwood of wilting branches, but if it’s not there, continue removing small pieces of bark to expose sapwood closer to the main stem. You may have to examine portions of the tree all the way back to the junction of the suspect branch with the main stem. The vascular discoloration can vary in prominence depending on tree species and sometimes isn’t visible at all, especially on young twigs. Diagnosis Conclusive diagnosis of verticillium requires laboratory culture of the pathogen from symptomatic wood. Other injuries to wood can also cause vascular discoloration. Don’t be too hasty to make the conclusion that verticillium is the cause, because if it isn’t, decisions about management and selection of replacement trees will be quite different. The Plant Disease Diagnostic Lab at Cornell, as well as diagnostic laboratories at other state universities, are able to provide this service - sometimes for a modest fee. Fortunately, verticillium doesn’t colonize its hosts with the speed that some other pathogens, like Dutch elm disease, do. There is time to do the culture, get the results and then plan a course of action. The sample you send to the lab should preferably be a 1 inch or larger diameter symptomatic branch (but NOT DEAD) that is 8-12 inches long. Life cycle V. dahliae can persist in the soil as resting structures called “microsclerotia” for many years without a host. When roots of a potential host are placed near the fungus, exudates from those roots stimulate the microsclerotia to germinate, and the fungus attempts to invade the plant. Wounded roots are especially likely to be colonized. Once infection has occurred, verticillium grows upward within the xylem vessels (the vascular tissue that transports water) of its host, causing the plugging that eventually leads to wilt. It apparently does not grow well from one growth ring to the next, so new vascular tissue, including that surrounding previously infected wood, must usually be colonized by new root infections each year. The microsclerotia, however, do function as large, durable spores and can be spread in contaminated soil, on infected roots, or even in some infected fruit. Management There is no fungicide treatment available to control verticillium wilt. However, some other measures may be taken to prolong the life and to improve the aesthetic value of an infected tree. Management of this disease includes proper pruning, watering and fertilizing. If so little of the crown is affected that branch removal will still leave an acceptable specimen then prune symptomatic branches back to their junction with the next largest asymptomatic branch. Severely infected trees, which would be unacceptable as landscape specimens after symptomatic branches are pruned, might just as well be removed completely. Water during dry periods, especially if they occur in summer or fall. Fertilize if needed with a low nitrogen, high potassium fertilizer. Excessive fertilization apparently increases problems with this disease. Do not replant in the same site with a verticillum-susceptible species because the fungus can survive in the soil for years. Instead, choose resistant or immune trees such as birch, ginkgo, sweetgum, mulberry, willow, hornbeam, hawthorn, honeylocust, crabapple, London plane, oak or mountain ash. Also, where maples are desired, be aware that red and sugar maples are more resistant than silver or Norway maples. Of the Norway maples, ‘Jade Glen’ and ‘Parkway’ have shown more resistance than other cultivars of the species. There is no guaranteed way to get rid of the fungus once the soil has been colonized. Where the disease has been confirmed and the tree has been killed, replacement with a verticillium-resistant tree may be the only feasible option. Verticillium spread by woodchips? Colleagues at the University of Wisconsin have looked at potential hazards associated with use of wood chip mulch from trees infected with Verticillium dahliae. They discovered that the pathogen will survive in chips for up to one year, albeit at relatively low levels. Furthermore, 13 months after Amur maple, green ash, and redbud saplings were planted in a potting mix amended with chips from a verticillium-infected tree, up to 28 percent of the trees became diseased. While there are still considerable differences between the “real world” application of wood chip mulch and the parameters used in these experiments, the threat of the chips is of sufficient concern that arborists are advised not to incorporate debris from verticillium-infected trees into chip piles planned for landscape use. Verticillium as a bioherbicide? Our colleagues at Penn State have recently made the intriguing discovery that verticillium wilt can be a devastating disease on invasive Tree-of-Heaven (Ailanthus altissima) in forest stands and Christmas tree plantations. In fact, preliminary results suggest that the pathogen may be far superior to traditional herbicides for suppression of the “weeds”. So far, there appear to be no adverse effects on maples, oaks, cherries and other desirable species, but additional work is needed to confirm that a purposeful introduction of verticillium would be safe for non-target organisms.
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| July is the best time to treat home lawns and golf courses for European chafer and Japanese beetle If your turf was damaged by grubs last year, now is the best time to apply imidacloprid, clothianidin, thiomethoxam or halofenozide to prevent grub injury to turfgrass this fall and next spring. New damage from grubs won’t appear again until this September or October. Golf course superintendents and professional turf managers can use Merit, Meridian, Arena, Aloft, Allectus, or Mach II. For homeowners, look for GrubEx, Season-Long Grub Control, Grub and Lawn Insect Control, or Grub Stop Once & Done. Granular insecticides are recommended for low maintenance turf where irrigation is not feasible. Applications of sprayable insecticides should be followed by 0.25 to 0.50-inch of irrigation. |
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| Japanese beetle biocontrol field day at Willow Metropark Turf and landscape professionals and the public are invited to a field day on July 30. I will give a brief presentation on long-term biological control of Japanese beetle with a protozoan pathogen, Ovavesicula popilliae. In addition, attendees will be given adult Japanese beetles infected with Ovavesicula popilliae, as a means to distribute the pathogen throughout Michigan. This event will be held July 30 from 11:00AM to 12:00PM at the Lajko Park Pavilion, immediately adjacent to Willow Metropark Golf Course, 22900 Huron River Drive, New Boston, Michigan. There is no charge to attend. For additional information, contact Dr. David Smitley, 517-355-3385 or smitley@msu.edu; or Mary Wilson (Southeast Region Extension Educator), 248-858-0887 or wilsonm1@msu.edu. Directions: http://www.metroparks.com/global/willow_map.php. |
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| Balsam fir sawfly Note: This article was originally printed in the June 24, 2005 issue of the Landscape Alert. Balsam fir sawfly The past few years in the northeastern portion of the Lower Peninsula we have seen severe defoliation from balsam fir sawfly. Growers and homeowners should begin to be on the look out for this sawfly. The larvae of balsam fir sawfly are dark green with darker longitudinal stripes and head and when mature are about a half-inch long (photo 1). They feed on the previous year’s growth of its preferred species balsam fir but will also feed on Fraser fir and spruce. Typically, we don’t get calls until the tree starts showing reddening of the interior needles in July (photo 2). Part of the difficulty is that these tend to be in the crown of the tree and your may not able to see the larvae on larger trees. Treat infested trees as soon as you see the larvae. Make sure to get good coverage.
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| Gypsy moth spray window update Growers should note that for Zone 5 Lower Peninsula Counties only, the spray window closing date for all other compounds has been set as Friday, July 11. Due to cool weather, the closing date for Zone 5 Upper Peninsula counties has been delayed one week and has been set as Friday, July 18. This is the final update for the 2008 season.
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| Glyphosate injury on tomato Several tomato samples have been submitted to the lab over the past ten days with symptoms consistent with glyphosate injury. In most of these cases, the injury resulted from glyphosate spray drift likely from neighboring corn and soybean fields. Occasionally, the injury resulted from glyphosate contamination in the tank used to apply pesticides to the tomatoes. Specific symptoms of glyphosate injury will vary depending on several factors including exposure dose, tomato growth stage and growing conditions after exposure. Glyphosate is translocated inside the plant to the newest meristematic regions; therefore the newest growth will be most injured. Tomatoes injured with glyphosate will have distorted new growth with cupped, fringed and small leaflets. Often, the newest leaves will contain a proliferation of buds and small leaflets. Many of the leaflet bases will contain a yellow to white discoloration –a diagnostic clue of glyphosate injury on tomato.
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| Fallen oak branches signal the work of the twig pruner This week several county extension educators reported that they were getting calls from clients that were finding fallen oak branches littering their yards. Many described the end of the branch as being neatly cut off like it had been pruned. This mid-season pruning is work of the twig pruner, Elaphidionoides villosus, (Coleoptera: Cerambycidae). This is one of our more damaging longhorned borers, which are normally considered secondary invaders of declining trees and shrubs. The twig pruner attacks healthy twigs and small branches. The twig pruner cuts through the twig from the inside, but leaves the bark intact. For a short time the injured branch remains on the tree, but eventually succumbs to the wind, breaks off and falls from the tree. A small oval shaped hole in the end of the branch is a tell-tale sign of the twig pruner. Look closely for this hole because the larva usually packs the opening with a frass plug to keep out predators and other unwanted guests. Twig diameters at the point of the cut usually range from about three-eighths to three-quarters of an inch. Common host trees are reported to include oak, hickory, pecan, walnut, basswood, redbud and hackberry. Reports of the life cycle of the twig pruner vary somewhat. As we understand it, the females lay eggs in small twigs near the ends of live branches in late spring. The larva eats the inside of the twig, then bores into the center of the branch and tunnels downward. When nearly fully grown, the larva severs the twig or branch by tunneling in circles from the center outward to the bark. Pruned twigs or branches soon break and fall. The larva continues to feed in the severed twig until it pupates. Winter is passed in the severed branch. Although the sight of many severed branches on one’s lawn can be alarming, there isn’t much that can be done other than picking up the mess and getting on with our lives. Some suggest this pest can be readily controlled by gathering the pruned twigs and burning them. We have our doubts about this. Control with insecticides would require a persistent insecticide and a thorough properly timed spray application. For this reason, spraying is not recommended.
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| Big ol’ hairy spiders Jerry Lindquist, County Extension Director, in Osceola County sent us a very impressive wolf spider that a client had found under a tent in a backyard in Mecosta County. Wolf spiders are among our biggest and hairiest spiders. I get the sense that many people believe that the bigger and hairier a spider is the more dangerous it is likely to be. Wolf spiders and a big hairy jumping spider known as the daring jumping spider, Phidippus audax, are among the spiders that are most commonly submitted to lab. The truth is more likely to be that we have more to worry about from frail anemic looking spiders, particularly, the yellow sac spiders, Cheiracanthium inclusum and C. mildei, (Miturgidae). Yellow sac spiders can be found walking about on foliage; under leaf litter, stones, and boards; and on buildings under the window sills and siding, in addition to the corners of walls and ceilings within homes. They probably account for more spider bites than any other spider and their bites are sometimes misdiagnosed as brown recluse bites by health care providers. C. inclusum is indigenous to much of the United States (except the northernmost states), while C. mildei, an introduced species from Europe, was found throughout much of the Northeast. Yellow sac spiders are active hunters, searching for prey rather than capturing it within a web. It is during these nighttime hunting trips that the spiders encounter humans and bite when they become trapped between a person's skin and sheets, clothing, shoes, and the like. Yellow sac spider retreats may be found outdoors under objects or indoors in the corners of walls and ceilings. These retreats are silken tubes or sacs in which the spiders hide during the daytime. In homes with light, neutral-colored walls and ceilings, the retreats may go unnoticed, as they are small and blend in with the background coloration.
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| Larder beetles We received several samples of larder beetles this past week. Larder beetles, Dermestes lardarius ( Dermestidae) are closely related to the carpet beetles that seem to be permanent guests in our homes. Larder beetles get their name from the days when we didn’t have refrigerators and people stored their cured meats in a larder. Larder beetles took advantage of this food source and fed on the cured meats while they were stored. Yech! Like their smaller cousins, the carpet beetles, larder beetles are protein scavengers. Both the larvae and adults feed on items such as fur, hair, hides, feathers, and occasionally stored products such as dried fish, pet food and cheese. In the house, however, the most likely source is dead insects or other animals (boxelder bugs, attic flies, ladybugs, mice, etc.) that have accumulated inside walls or attics. This beetle is also found in bird nests, animal remains, and bee and wasp nests. If the source of larder beetles can be determined, then control can be achieved by discarding or cleaning infested woolens, feathers, furs, hides and so forth. However, in the more typical, general infestation, the source is probably the dead insects within attics and wall voids where removal or sanitation is not practical. Cleaning is still recommended. Thoroughly vacuum clean cracks and crevices in the areas where larder beetles are found. The adult beetle is just under three-eighths of an inch long and dark colored with a pale yellow band across the center of the beetle. The grub or larva is dark brown and very hairy in appearance with two curved dorsal spines on the tail end. There may be several generations of the beetle each year. The larvae are known to burrow into wood to construct chambers in which to pupate. We have some reports of structural damage to hen houses because of this behavior. The first step in larder beetle control is to locate and dispose of all infested material. This may be difficult, or next to impossible if the beetles are feeding on dead insects in wall voids and other hidden sites. After the infested material is removed, the immediate area should be thoroughly sprayed with an indoor formulation of a residual insecticide. Do not use these products in cupboards or food preparation surfaces. When they are found in cupboards, all food material should be inspected and discarded if found to be infested. Be sure to read and follow all instructions and safety precautions found on the label before using any pesticide.
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| Weather news An area of low pressure moving through the Great Lakes region will bring the likelihood of showers and thunderstorms to Michigan Saturday, July 12, with some heavy rainfall totals (greater than 1.00 inch) possible. Cooler and drier weather will develop statewide Sunday as high pressure moves into the region. Fair and dry conditions are also expected for at least the first half of next week as well. Temperatures Saturday should range from the 70s north to the upper 80s in the south. Cooler readings are likely Sunday and Monday, with a gradual warming trend by mid-week. Look for highs Monday from the upper 60s to low 80s, with lows generally in the 50s. Latest medium range forecast guidance suggests upper air troughs across northwestern and northeastern sections of the United States, with a broad ridge across the middle of the country and a relatively active weather pattern for the Great Lakes region. The National Weather Service 6‑10 day outlook covering July 16 through July 20 calls for near normal temperatures across the state, with above normal precipitation totals. The outlook for the 8‑14 day period (July 18 - 24) calls for above normal temperatures and above normal precipitation. |
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