Landscape and nursery
§ Splitbark and glyphosate is there a relationship?
Turfgrass
§ Turf diseases getting pesky in turf
§ Michigan Turfgrass Field Day
Around the home
§ The summer of our discontent
§ Strawberry root weevils are at it again
§ Megarhyssa wasps
§ Spotted Mediterranean cockroaches
Other news
§ Weather news
Next issue August 22
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.
"The economic cost to the
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
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.
Kevin Frank
Crop and Soil Sciences
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.
Kevin Frank
Crop and Soil Sciences
The Michigan Turfgrass Field day is scheduled for Wednesday,
August 20 at the
Michael Kaufman
Entomology
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
One of the indicators of summer floodwater populations is
the appearance of a very large species, the largest in
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
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
In the area of “what’s new” for mosquitoes in
Howard Russell
MSU Diagnostic Services
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
Howard Russell
MSU Diagnostic Services
Two people sent me photos of Megarhyssa wasps this
week. One came from Jon Stauffer in
The long-tailed Megarhyssa wasps (Hymenoptera: Ichneumonidae) are the largest ichneumons in
Howard Russell and Duke Elsner
MSU Diagnostic Services and MSUE
Up until a few years ago, this small European species of
cockroach was only known to occur in the
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
Jeff
Andresen
Agricultural Meteorology
Geography
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
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.
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