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| Vol. 23, No. 15, August 8, 2008 |
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| In this issue Landscape and nursery Splitbark and glyphosate is there a relationship?Turfgrass Turf diseases getting pesky in turf Michigan Turfgrass Field DayAround the home The summer of our discontent Strawberry root weevils are at it again Megarhyssa wasps Spotted Mediterranean cockroachesOther news Weather newsNext issue August 22 |
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| Splitbark and glyphosate is there a relationship? The following article was written by Candace Pollock from Ohio State University based on research conducted by Dr. Hannah Mathers and has information that would be of interest to Michigan nursery and landscape professionals - Thomas Dudek ,MSU Extension Educator, Grand Haven, Michigan. Glyphosate products, like Roundup, may be killer on weeds, but researchers are finding that the product may also do damage to landscape and nursery woody plants. Hannah Mathers, an Ohio State University Extension nursery and landscape specialist, said that glyphosate applied improperly or in too high of a dosage is causing a phenomenon known as split bark, where, through the tree's uptake, the chemical is deteriorating the bark structure and destroying the winter hardiness of the plant. The cosmetic damage makes the plant unsaleable, and is costing the landscape and nursery industries millions of dollars per year in damaged product. |
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| "The economic cost to the U.S. nursery industry from bark cracking is conservatively estimated at $6.6 million a year. That's roughly 2.5 percent of finished inventory," said Mathers, who also holds an appointment with the Ohio Agricultural Research and Development Center. "Add to that the conservative estimate of $14 million in landscape tree failures, and we've got a national phenomenon that has been happening for several years but only now are people taking seriously." Mathers is teaming up with agricultural company, Monsanto, to help develop a glyphosate product that is safer to use for weed control around landscape and nursery woody plants. She has been leading national public research on the impacts of glyphosate on woody plants, as well as educational efforts on which glyphosate products to use and how to properly apply the chemical. "For a long time, industry felt that split bark was an environmental problem, driven mainly by cold temperatures. But we were receiving reports of split bark in warmer parts of the country, such as Georgia, the Carolinas and California. Why would it be a cold issue if splitbark is happening in those areas?" said Mathers. "Winter temperatures are part of the problem, but only because glyphosate weakens the bark structure enough to cause the trunks to split under stress. There's a large body of national research that supports those findings." Mathers said that the first step in controlling split bark is education: recognizing that glyphosate could be a contributing factor, which glyphosate product to use, and using that product properly. "The first thing I tell nursery and landscape professionals is to use glyphosate only when necessary," said Mathers. "We want to stress pre-emergent glyphosate applications to kill weed seedlings, rather than a post-emergent application that kills the entire weed plant. It reduces the impact on woody plants, as well as saves money. Adoption of integrated weed management programs with reduced reliance on glyphosate can cut herbicide expenses and application labor by up to 50 percent." In situations where glyphosate is required, users should pay attention to which product they apply. Research has shown that it's not the glyphosate itself that is causing split bark, but the surfactant found in some glyphosate products that is causing the problem. A surfactant is a wetting agent that allows for easier spreading of the chemical, and increases uptake of the chemical in woody plants. Surfactants are known as adjuvant loads on glyphosate product labels. "When glyphosate use is necessary, use a glyphosate product around woody plants that has no adjuvant load," said Mathers. "Products that have a full adjuvant load are the worst around ornamental plants because of the increased potential for uptake of the glyphosate by the surfactant into the bark." Fourteen registered glyphosate products contain no adjuvant load. They include: Backdraft, Campaign, Expert, Extreme, Fallowmaster, Fallow Star, FieldMaster, Glypro, Landmaster BW, Land Star, ReadyMaster ATZ, Rodeo, Roundup Custom and RU SoluGran. Mathers also encourages nursery and landscape practitioners to apply glyphosate products properly. An Ohio State University Horticultural Research Institute-funded project conducted last year, found that many growers and nursery/landscape professionals were using glyphosate indiscriminately -- making applications (one quart per acre) as frequently as eight times a season, or approximately every 2.5 weeks; removing suckers with glyphosate products; and applying product so close to woody plants as to increase uptake through drift exposure. "Glyphosate should not be used to remove suckers, there should be a 30-foot buffer between the weeds you are spraying and the woody plants, and glyphosate should not be applied so frequently," said Mathers. "The formulations for glyphosate have changed over the years. I don't think people realize that the glyphosate they use now is more potent than older products they are used to. Plus, more generic brands are now available and they are cheaper to come by, so users are getting more lax in their applications." Mathers said that glyphosate with surfactants are dangerous for woody plants because it takes years for the plant to break down the chemical once it's taken up. Research has shown that one single low dose of glyphosate stays in the plant for at least a year. "Just imagine what kind of damage you are doing to a woody plant when you apply glyphosate two times a month," said Mathers. "Glyphosate injury is also difficult to diagnose because symptoms may not be present for up to two years after glyphosate absorption." In addition to split bark, other symptoms include witches broom, stunting, loss of apical dominance, individual dead limbs, chlorosis and death. Woody plants most susceptible to glyphosate uptake include: Pyrus species, especially Callery pears; Prunus species, especially Yoshino cherry and Kwanzan cherry; Crab apples; Sycamore; Serviceberry; Hawthorn; Mountain Ash; Black Gum; Paper bark maple; Japanese maples, especially variety dissectum; Norway maple, especially‘Emerald Queen'; Red maples; Dogwood, especially Kousa dogwood; Magnolias, especially Magnolia ‘Elizabeth’;and the yellow magnolias such as Magnolia ‘Butterflies’, ‘Sawada’s Cream’, Magnolia ‘Yellow Bird’ and Magnolia ‘Yellow Lantern’. Specifically, glyphosate uptake leads to an accumulation of a type of acid called shikimic acid that results in a reduction of phenolics -- plant compounds that serve a variety of roles in plant development and survival including defense against pathogens. Research has found that the more glyphosate is taken up by the plant the higher the shikimic acid levels. In addition, glyphosate stays within the plant for years, being stored in the roots with sugars in the summer and fall, and then translocating to areas of the plant where growth takes place in the spring and continuing to cause injury. Mathers said that until safer glyphosate products are developed, a change in weed management practices in the nursery and landscape industries is required to control the split bark phenomenon. |
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| Turf diseases getting pesky in turf Dollar spot and red thread are two diseases that have been appearing in turf in the last few weeks. For lawn height turf, these diseases are generally considered to cause cosmetic damage and will usually not create enough damage that would require any fungicide applications. Red thread is a pesky disease that we have been receiving reports on from home owners. Red thread, if a problem, is usually found in under fertilized or slightly starved turf. With the relatively good growing weather that we’ve experienced throughout much the year, many of the fertilizer applications that were applied earlier in the season have probably run out and now the turf could probably use another fertilizer application. Red thread is often found in areas dominated by fine fescues or perennial ryegrass. Red thread is easily identified by the pinkish-red mycelium that is threadlike and surrounds the leaf blade. In some extreme cases it might remind you of miniature balls of pink cotton candy. The areas infected by red thread will die and the turf may appear wilted. The simplest fix for red thread is to apply a quick release nitrogen carrier such as urea at about 0.5 lb. N/1000 ft.2 to encourage turf growth to mask the symptoms. Dollar spot is also a disease that occurs on turfgrass that might be under fertilized. This is especially true on home lawn situations, and just like red thread a light fertilizer application will help the turf recover from the symptoms. I’ve also spotted some brown patch in tall fescue lawns. Brown patch becomes problematic when the weather starts to feel really uncomfortable – think hot and sticky. Brown patch occurs in turf as circular patches that can be a few inches in diameter to several feet. In closely cut turf, such as on golf course fairways or greens, often the circles are very distinct and a smoke ring appears on the outer edge of the diseased ring. In lawn height turf the individual leaf blades may initially appear water soaked and dark with their eventual fate to be turning a darkish brown color. Whereas red thread and dollar spot are considered diseases of under fertilized turf, brown patch is often associated with well fertilized, lush turfgrass growth. The cool temperatures should put the freeze on brown patch for now and will help stimulate turfgrass growth to grow over the damage created by all of these diseases. |
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| Michigan Turfgrass Field Day
The Michigan Turfgrass Field day is scheduled for Wednesday, August 20 at the Hancock Turfgrass Research Center on the campus of Michigan State University. There will be morning research tours focusing on golf turf management and commercial turf/athletic field management. In the afternoon there will be in-depth workshops on diseases, weeds, athletic fields, and sprayer calibration. MDA pesticide recertification credits (category 3A) will be available for the morning and afternoon tours, two credits for the morning tour and two credits for the afternoon workshops. GCSAA education points, 0.20 for the morning and 0.20 for the afternoon workshops, will be available for golf course superintendents. On-line registration is available at: http://www.michiganturfgrass.org. |
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| The summer of our discontent Although the lack of continued substantial rains in the past few weeks has tempered mosquito populations, it has already been a noticeably bad year for the hosts of these blood-feeding insects. In my locale, it has easily been the worst mosquito “season” in the past decade. Why is this so, what can you do about it, and what might it mean for mosquito-borne disease risks? The simple explanation is that earlier in the summer there were several major rain events that both induced hatching and sustained larval habitats. In my area, there were two storms that produced over four inches of rain. This helped launch broods of summer floodwater mosquitoes (e.g., Aedes vexans and A. trivittatus). In June, these species overlapped somewhat with remaining spring emerging species (recall we had good snow cover and saturated soils in early spring) to create a large crop of nuisance biters. Additionally, a cattail marsh species, Coquilletidia perturbans began to emerge in June to add to the problem in some areas. Heavy floodwater mosquito populations often result from the hatching of eggs laid several years ago. Think of them as mosquito “seeds.” The eggs are laid in ground depressions that may not hold standing water every year. When we get large rain events in the summer, these habitats produce mosquitoes from the “seed bank” to add to the normal background populations. I’m pretty sure this occurred in many parts of Lower Michigan, as I’ve seen standing water in areas that are usually dry at this time of year. If continual cycles of flooding and drying occur during a single summer, the floodwater mosquitoes can continually breed (multiple generations each year) and reach intolerable levels. The good news is that large, flooding rainfall events didn’t continue into July, so many larval habitats have disappeared and adult populations are diminishing. However, another series of storms with heavy rainfall could very well induce another outbreak. Since we’re heading into the part of summer when species from permanent water bodies are also beginning to peak, our misery index could easily rise again. One of the indicators of summer floodwater populations is the appearance of a very large species, the largest in Michigan, commonly called “gallinippers.” This is Psorophora ciliata (see photo) and it can be alarming when it lands on your arm to attempt to feed. Adult females can be over a half inch long in body length and they have very hairy legs with yellowish bands. They are never very abundant, but you won’t forget them if one tries to bite you. On the positive side, their larvae feed upon other mosquito larvae, so they have a beneficial aspect. How does one deal with the onslaught of summer species? Unfortunately, when they’ve reached the adult stage in large numbers, options are few. There are many effective backyard spraying and fogging treatments that typically use a synthetic pyrethroid (e.g., permethrin) as the active ingredient. Some can be sprayed at yard borders and have residual effect. Obviously, you will want to strictly adhere to application instructions and restrictions. Pyrethroids have low mammal and bird toxicity, but overspray into ponds, for example, might harm fish. Note also that these compounds are not mosquito specific, so most other insects will be affected. A commercial option that should be avoided is the timer-based automatic sprayers. These units (called “Mosquito Misters”) are analogous to automatic sprinkler systems and simply spray or mist insecticide from a reservoir at the determined time intervals from a series of nozzles placed in and around the property. This system is costly, inefficient, and violates the sound principles of integrated pest management. If mosquito problems on your property are severe enough for you to consider such a system, I suggest that you contact a mosquito control company instead. Consider hiring a service as part of a neighborhood group, as mosquitoes can and will move around frequently from yard to yard. Some of the floodwater species are known to travel miles in search of hosts. If you’re like me and prefer not to deal with broad-spectrum adulticides, then your options lie in avoidance (stay inside!) and the judicial use of repellents. Spending the evening on your deck or patio can also be made more tolerable with some well-placed fans. There is an increasing variety of mosquito repellants available that can be applied to exposed skin and many common fabrics (cotton and nylon are OK, but certain synthetics such as rayon may not hold up to higher concentrations of DEET). DEET-based products remain the standard for effectiveness and safety, but relatively new products with picaridin (supposed to be less irritating than DEET, sold as Cutter Advanced) or lemon-eucalyptus oil derivatives (a Repel product) are quite effective. Other products based on botanical derivatives (e.g., Bite Blocker with soybean oil) can be effective for short periods of time, but if you want something to last for more than two hours after application and to work for ticks as well as mosquitoes, use one of the products mentioned above. There are also several lines of clothing impregnated with permethrin (e.g., Buzz Off) that keep mosquitoes from landing on materials. You can also apply this to several types of fabrics yourself and it’s supposed to last through several washings. Note that this is the same principle used in bednets to fight malaria in Africa, but also note that the clothing doesn’t provide a whole body shield. Mosquitoes will readily land and bite on exposed skin adjacent to the material. Unfortunately, there are no landscaping plants that are effective repellants, and citronella candles have not been shown to be more effective than other smoke producing candles in keeping mosquitoes at bay. I’d love to be able to recommend attracting bats as a means to reduce mosquito populations, but the idea that they are mosquito-eating machines is simply a myth. Of course they can and do eat mosquitoes, but they almost certainly could not survive by doing so. The myth arose from a study that reported bats would need to eat several thousand mosquitoes (or mosquito-sized insects) a night to meet energy demands, and from counts of mosquitoes eaten by bats in cages where they were the only prey item. Any accounts of bats controlling mosquito populations are anecdotal, as are those indicating birds such as purple martins are effective. You should also be aware that there’s been a spike in the numbers of rabies-positive bats this year, so it’s hard to recommend any practice that would increase the potential for contact with these creatures. Likewise, it would be nice to be able to recommend propane-powered devices such as Mosquito Magnets that attract and kill mosquitoes via carbon dioxide (sometimes with an octanol supplement) plumes and a fan. However, there is no evidence that they reduce biting rates in a realistic setting and in fact may be drawing in mosquitoes from other areas. The running joke is that if you want these traps to work for your yard, buy one for your neighbor. They are also not equally effective in trapping all species; we know this from our own mosquito traps that are based on the same attractants. The only study showing substantial reduction in biting rates after use of these devices took place on a very small island with a well-defined mosquito population. The standard dogma about eliminating breeding sites on your property, by eliminating or frequently changing any standing water such as that in birdbaths, still holds true, but it will have little effect on the crops of floodwater mosquitoes that have been the bane of this summer thus far. As mentioned, most of the mosquitoes biting you during the day while you’re trying to weed your garden, or in the evening when you’re relaxing on the patio, have developed elsewhere and have potentially flown into your backyard (unless you live along a floodplain) from miles away. This is not to say that your efforts to eliminate breeding sites are useless. The artificial containers around your home can be excellent larval habitats for many of the species that transmit human diseases. The large populations of nuisance mosquitoes seen this summer do not necessarily portend an increase in risk of mosquito-borne disease. Some floodwater species appear to be competent vectors of West Nile virus, for example, but it’s thought their role is minor. They have, however, been implicated in transmission of dog heartworm, so make sure your pets are current with their medications. The primary vectors of West Nile, species of Culex mosquitoes, do not appear to be in unusual abundance this year and our testing of mosquito pools for West Nile virus and other mosquito-borne viruses have not yielded a single positive. It may simply be that the disease is slower to emerge this year because of climate conditions or bird population factors. West Nile virus and similar diseases tend to be more pronounced in hot, dry years and I wouldn’t characterize the first half of our summer as such. The same conditions (heavy rains) that encourage high populations of floodwater mosquitoes may be washing out some larval habitats (e.g., storm water catchbasins) of the Culex species. However, be aware that late summer is usually when Culex populations peak and they also appear to be more likely to feed on humans during this period. Although the risk may be relatively lower this year, I’d still urge precautions and the use of repellants, particularly during the evening and nighttime hours. In the area of “what’s new” for mosquitoes in Michigan, you’ll be happy to know that we have a recently established invasive species. Ochlerotatus (Aedes) japonicus actually arrived here in about 2003 (1998 in the eastern United States) and we’ve been tracking its progress in certain areas. It’s a medium-large mosquito with striking markings (see photo), but isn’t necessarily an aggressive biter. Its original range is Japan and northern Asia, and can easily overwinter in our climate in contrast to other invasive mosquito species such as the Asian tiger mosquito. It appears to be a highly competent vector of West Nile virus and similar diseases, and we know it feeds on birds and mammals, including humans. The reason I point it out here, is that it seems very well-adapted to breeding in artificial containers around human dwellings, with a particular fondness for plastic. I’ve found it in buckets, dog dishes, kiddie pools, artificial ponds (with plastic liners) and a number of miscellaneous containers. In some cases, it appears to be displacing native mosquitoes including Culex. We don’t know its role in any disease cycle yet, but it’s clearly one to watch in the event of any new disease introduction into North America. If anyone notices large, dark larvae in plastic containers around the house or yard, please place a few in alcohol (rubbing alcohol is fine) and send them to me.
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| Strawberry root weevils are at it again The strawberry root weevils, Otiorhynchus ovatus (Coleoptera: Curculionidae) are harmless beetles that become a household nuisance when they invade homes during the summer months. In some cases their numbers can be enormous. The weevil is about a quarter of an inch long and dark brown in color. The abdomen is quite rounded, and when viewed in profile the weevil’s short snout can be easily seen. The larvae feed on small roots of wild and cultivated strawberries, brambles and some ornamental plants. Adult weevils are wingless and enter dwellings through loose fitting doors, windows, screens, and other small cracks and openings. They crawl everywhere through the home: bathrooms, cupboards, floors, walls and ceilings. The good news is that they don't do anything else. They don't bite or sting, eat your house or stored food, infest your pets, or transmit diseases. The best, long-term way to control these pests is to caulk and seal the outside of the house to prevent them from entering. The best method of controlling the weevils inside the home is to vacuum them up. If they become terribly numerous and a more aggressive method of control is desired, a persistent insecticide can be applied to the ground around the outside of the home to provide a 10 ft. treated barrier to help prevent their entry. Be sure to read and follow all instructions and safety precautions found on the label before using any pesticide
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| Megarhyssa wasps Two people sent me photos of Megarhyssa wasps this week. One came from Jon Stauffer in Clinton County and the other from Cathy Patterson in Tuscola County. The long-tailed Megarhyssa wasps (Hymenoptera: Ichneumonidae) are the largest ichneumons in Michigan. These impressive wasps frequently attract people’s attention because of their size and long tail-like ovipositor that is as long as or even longer than the body. The ovipositor has two sheaths which may make the insect look like it has three long tails. Do not panic; they will not harm you. The ovipositor (the bit that looks like a stinger) is for laying eggs not stinging people. The long flexible ovipositor is used to drill deep into dead or dying trees to deposit an egg into the body of a wood wasp or horntail larva. When the egg hatches, the Megarhyssa larva eats the horntail larva from within.
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| Spotted Mediterranean cockroaches Up until a few years ago, this small European species of cockroach was only known to occur in the United States in Massachusetts and southeast Michigan. Then Duke Elsner found it in Grand Traverse County and according to the Dukester, it has been expanding its range in and around the Traverse City area ever since. The spotted Mediterranean cockroach, Ectobius pallidus (Blattellidae) was first discovered in the United States in 1948 on Cape Cod. I don’t know when it first arrived in southeast Michigan. Sometimes called the tawny cockroach, this species is normally encountered outdoors and generally does not infest food or goods indoors. It can become a nuisance when attracted to dwellings by lights. This is a pale-brown cockroach that is smaller than the German cockroach and lacks the dark lines on the pronotum that characterize the latter. The wings have many tiny, dark spots that can be seen only with the aid of a hand lens. The nymphs are also pale brown. This insect can be discouraged from entering homes by spraying a persistent insecticide around the outside of the home. Be sure to read and follow all instructions and safety precautions found on the label before using any pesticide. See photos of the spotted Mediterranean cockroach at: http://bugguide.net/node/view/26905 |
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| Weather news During the past one to two weeks, a broad upper air ridge has persisted across much of the central United States, resulting in oppressive heat across sections of the southern and central Great Plains and generally drier than normal conditions across much of the Upper Great Lakes region. Recently, the ridge axis has shifted westward into the Rockies, leading to the development of a troughing feature across the Great Lakes and a period of cooler than normal weather. In the short term, a weak upper air disturbance passing north to south through the state Saturday will lead to the chance for showers and a few thundershowers, especially in eastern sections of the state. Rainfall amounts are expected to be limited with most totals remaining in the 0.10-0.25-inch range or less where rain falls. Cool and mostly dry weather is expected Sunday, August 10. Temperatures this weekend will remain below the climatological normals, with highs ranging from the upper 60s north to near 80°F south and with lows from the upper 40s north to near 60°F south. A weather system approaching from the west will bring the next chance for significant rainfall by late Monday or Tuesday of next week. In the medium range period, forecast guidance suggests a general continuation of the upper air pattern mentioned above. Both National Weather Service 6 ‑ 10 day, covering August 13-17, and 8 ‑ 14 day, covering August 15-21, outlooks call for below normal mean temperatures state- and region-wide. Precipitation totals are forecast to range from near normal levels in northwestern sections of the state to above normal levels in the southeast during the 6 - 10 day time frame and remain at near normal levels statewide during the 8 - 14 day period. New long lead outlooks Latest long lead forecast guidance suggests that the El Niño Southern Oscillation (ENSO) index will remain near neutral for the next several months into early 2009 at least. Thus, while some impacts of the recent past La Niña event may persist for another month or two(including increased chances for hurricane activity in the northwestern Atlantic Basin), ENSO is expected to have little or no influence in the outlook for the next several months. The latest NOAA Long Lead outlook for August calls for mean temperatures in Michigan to remain in the climatology scenario with near equal odds of below, near, and above normal values. The outlook for rainfall suggests above normal totals across some western sections of the state, with near the equal odds scenario elsewhere. Further ahead, the outlook for the three-month August through October period calls for increased odds of above normal mean temperatures statewide. Precipitation totals for this frame are forecast to remain in the climatology/equal odds scenario. |
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