Vol. 20, No. 18, September 23, 2005

Thomas A. Dudek
Extension Horticulture Educator

As the calendar turns from September to October, it’s time to review your nursery rodent management program for the upcoming winter months. This year in West Michigan it has been very dry and voles may be more of a problem do to the lack of food sources in the field margins and borders. Generally speaking, most nurseries have problems with meadow voles or pine voles. Some growers call them meadow mice or field mice. They are all voles!

Voles eat a wide variety of plant parts including seeds, tubers, rhizomes as well as bark on tree trunks and plant roots. In most Michigan nurseries the economic damage is to roots and bark on trunks and is why growers do not tolerate these pests. They can outright kill a tree or woody plant. In the late summer and fall they store seeds, bulbs and rhizomes for the winter. They generally consume bark in the winter months when other food sources are unavailable. Voles are active day and night with peak activity during the dawn and dusk hours. Voles do not hibernate. Their home area is usually in a quarter of an acre or less. There are two voles that cause nursery growers problems and they can be distinguished by the characteristics listed in the accompanying table.

Management of voles takes on an integrated pest management approach in the nursery. One should first determine which vole your nursery is dealing with. Use the accompanying chart or use the “apple sign test” developed by North Carolina researchers. This test is described in: NC State Wildlife Damage Notes: “Voles in Commercial Orchards and Ornamental Nurseries”. It can be downloaded from the web: http://www.ces.ncsu.edu/nreos/wild/wildlife/wdc/voles.html

For meadow voles, closely mow the nursery fields or areas around polyhouses where the trees or plants are located. A 4 foot grass-free strip on each side of the tree row is recommended. Also, wrap quarter inch hardware cloth 5 to 6 inches high around the tree trunks or plastic tree guards will help discourage meadow voles. Rodenticides treatments are also recommended both in the field and in polyhouses. Be sure to apply rodenticide baits early in the overwintering season and check them frequently during the first two to three weeks after application to determine the need for reapplication.

Pine vole pest management rests solely on the use of rodenticides. Once the problem has been determined to be pine voles rodenticides should be applied only in those areas that are impacted. Use the “apple sign test” once in the fall and once in the spring. Place all rodenticide baits in containers such as: pot-in-pot, 1.5-inch diameter PVC pipe, commercial bait stations etc… since these baits are toxic to all forms of life. Growers have unknowingly killed neighbor’s dogs and cats that sniff the bait and mistake it for food. Replace baits if they become wet. If dealing with pine voles, apply baits to the burrows only, not to bare ground. Avoid placing baits in heaps or piles. Always read the label as these are pesticides and can cause damage to non-targeted animal life!

Rodenticides for voles include the anticoagulants that have either the active ingredient brodifcoum (Havoc, Boothill) or diphacirone (Ramik Green). These pesticides are more toxic to rodents than other mammals or birds. When used according to the label they are safer than some of the others. Anti-coagulants are slow acting toxicants and can take from 5 to 15 days to cause death. Multiple feeding is necessary to be effective. The other group of rodenticides is the “single dose” zinc phosphide products (Eraze Rodent Pellets, Prozap, Ridall-Zinc II, Motomco Rodenticide Ag and ZP Rodent Bait Ag). These products are all highly toxic and are most commonly used to control voles. Zinc phosphate baits are most often placed in runways, burrow entrances and locations where voles are active. Application of non-treated bait prior to applying the toxic bait may be necessary if bait shyness has developed (two or more treatments of a zinc phosphide that do not work) to these single dose products. Always read the label for rates and safety precautions.

As a side light, on a small scale – trapping can work to remove voles. Mouse traps set in the fall or late winter baited with peanut butter/oatmeal or apple slices is effective. Covering the trap also with a box, grass, etc. helps with your success rate.

Finally, encourage hawks and owls around your nursery as they are great predators. Build perches using 10 to 15 feet high poles with a 1- to 2-inch diameter perch on top. This provides raptors with a great overlook in the nursery. One perch for each five acres is usually sufficient.

Willie Kirk, Plant Pathology
Tom Dudek, Extension Horticulture Educator
Mike Bryan and Barry Menser, Michigan Department of Agriculture

The Michigan Department of Agriculture (MDA) restricted, sampled and verified tobacco ringspot virus (a nepovirus) on Hemerocallis, 'Purple D'Oro,' daylily. This is a common variety, and may highlight that viruses could be an emerging problem in daylilies. Although the source is not known at this time, this virus is transmitted by a vector; a nematode – also, non-specifically, by insects and mites Aphis gossypii, Myzus persicae, Melanopus sp. Epitrix hirtipennis, Thrips tabaci (possibly nymphs) and Tetranychus sp.; Xiphinema americanum; Dorylamidae. The virus is lost by the vector when it molts and does not multiply in the vector. The virus is not transmitted congenitally to the progeny of the vector and can be transmitted by mechanical inoculation. This virus is not known to be transmitted by contact between plants, by seed or by pollen to the seed. Symptoms of the virus are shown in Photo 1.

Host list

The MDA also restricted, sampled and verified tobacco streak virus (ilarvirus) on Rudbeckia 'Goldsturm.' Most of the plants (about 100 or so) at this nursery dealer were infected. This is the first report of this virus on perennials in Michigan. The source is not known at this time. The virus is transmitted by a vector; an insect; Frankliniella occidentalis and Thrips tabaci; Thysanoptera (possibly by allowing virus from the surface of infected pollen to enter through feeding wounds). The virus is also transmitted by mechanical inoculation, grafting, by seed (in Chenopodium quinoa, Phaseolus vulgaris, Datura stramonium to different extents) and by pollen to the pollinated plant. The virus is not transmitted by contact between plants. Symptoms of the virus are shown in Photo 2.

Kevin Frank
Crop & Soil Sciences

The calendar has now officially confirmed that it is autumn, and the recent round of rains that swept across the state have provided some relief from the dry conditions that persisted in many areas. So now all of those turf practices that I discussed in the September 9Landscape Alert can actually be done. With the added soil moisture it should be much easier to core aerate to alleviate compaction, dilute/remove thatch and improve turfgrass rooting. So start your aerifier engines!

For non-irrigated turf areas, many people may have held off on the Labor Day fertilizer application because the turf was dormant. If you’ve received rain in your area the turf will respond quickly to the life renewing moisture and a fertilizer application now should help improve turf density after a tough summer. If you did apply fertilizer around Labor Day, it is not necessary to make another application now. Also, if you apply fertilizer now you probably don’t need to worry about the late fall application. So depending on your situation either apply fertilizer now and you’re done, or if you applied early in September wait until the late fall before considering another application.

What about late fall fertilization?
An effective late fall fertilization will benefit the turf by producing carbohydrate, encouraging early spring root growth, providing good fall and spring color and improving turf density so the turf will better compete with weeds next spring. The late fall fertilization is always a challenge for timing because it’s really tough to figure out when fall stops and winter begins. The rule of thumb is to keep a close eye on when the turf stops growing. When top-growth stops, that’s the time to put down that late fall fertilizer. Generally for Michigan, in the northern portions of the Lower Peninsula the late fall application would be about the last week of October and in the southern Lower Peninsula around the first or second week of November. Always make sure to apply the late fall application in advance of when the soil freezes, you never want to apply fertilizer to a frozen soil. Also, use fertilizers that have a high percentage of fast release/water soluble nitrogen because we want to have the nitrogen taken up by the plant quickly so it can start storing carbohydrates before winter sets in.

Still time to seed?
This is always a tough one because as with many things, it depends. You can certainly still put seed down and you’ll get germination and emergence, the challenge is that as we move closer to November the amount of time those young seedlings have to mature before winter arrives becomes shorter and shorter. Young seedlings are more susceptible to winterkill. Along the Grand Rapids/Lansing/Detroit corridor you are probably safe to seed until around October 1 and have enough time for the seed to germinate and survive the winter. If you’re north of that line and still want to seed, hope for a warm fall. Consider that seed is relatively cheap, and if you’re not doing a huge area, I wouldn’t worry too much, if it doesn’t survive the winter you’ve got some practice in this fall and will be ready to go next spring.

Broadleaf weed control
October and early November are the ideal time to control broadleaf weeds because the weeds are storing carbohydrates in their root system and are more susceptible to herbicide applications. So if your turf is being overtaken by a wide array of broadleaf bandits, applying an herbicide now could make the difference for next year. Apply the herbicides on a sunny day when rain is not in the forecast for 24 hours. We want the herbicides to dry on the leaf surfaces and not be immediately washed off. Also, make sure the turf is actively growing, cool weather and timely rains in the last week should ensure active growth in most areas. The reason we want to see actively growing turf and weeds is that if they are sitting dormant those herbicide applications won’t be very effective. There are many different herbicides that could be used including the most common three-way broadleaf weed control mixtures. As with any pesticide application always make sure to wear the appropriate safety attire and follow all label recommendations. The greatest shortcoming of killing broadleaf weeds at this time of year is that you really don’t get to watch them die. In many cases you may not see the obliteration of these weeds this fall but next year they won’t be there or will at least be reduced in numbers.

Mulching leaves
Well it wouldn’t be the final issue of the Landscape Alert without talking about mowing leaves into turf so here goes. The leaves are changing and soon they’ll be a falling, which means it’s time for you and me to start mulching. Okay that’s a pretty lame rhyme but you get the point. If you’re still of the belief that you need to rake leaves, come on over to the mowing side. Here’s what you need to know to successfully mow leaves into the turf. First of all make sure your mower has a sharp blade. After a long season of mowing, the blades may be dull at this time of year and trying to chop up leaves will be more challenging with a dull blade. Second, raise the mower as high as it will go and mow at your normal speed, don’t “rev” the throttle to the high jackrabbit setting and blaze around the yard. Try to mow the leaves when they are moist from the morning dew but don’t mow them when they’re really wet. This will prevent the leaves from blowing all over the place and will help with your allergies. Finally, don’t let the leaves pile up too high before you mow. Too high would probably be greater than 3 to 4 inches of leaf depth on the turf. Mulching leaves helps the turf by returning nutrients and organic matter. After a nice rain shower you usually can’t even tell that you mulched the leaves into the turf.

Steven Gower
MSU Diagnostic Services

Giant hogweed is a majestic plant that can grow as tall as 20 feet. Although attractive, giant hogweed is a public health hazard because it can cause severe skin irritation in susceptible people. The plant exudes a clear, watery sap that causes photodermatitis, a severe skin reaction. Skin contact followed by exposure to sunlight may result in painful, burning blisters and red blotches that later develop into purplish or blackened scars. The reaction can happen within 24 to 48 hours after contact with sap, and scars may persist for several years. Contact with the eyes can lead to temporary or permanent blindness. Wash immediately with soap and water if skin exposure occurs. If possible, keep the contacted area covered with clothing for several days to reduce light exposure.

Giant hogweed (Heracleum mantegazzianum) is a federal noxious weed, so it unlawful to propagate, sell or transport this plant in the United States. The U.S. Department of Agriculture (USDA) has been surveying for this weed since 1998 and has identified several infestations in Michigan. The USDA cannot check all of Michigan, however, so we need your help in locating sites of giant hogweed. If you see this weed, please report its occurrence to the Michigan Department of Agriculture (MDA), the USDA, Michigan State University Extension or MSU Diagnostic Services.

A new MSU Extension bulletin (E-2935) on giant hogweed in Michigan is now available at the Bulletin office for $0.50. This bulletin explains the health hazards of giant hogweed, how to identify giant hogweed and similar plants, and what one should do if you suspect it on your property.

A pdf of the bulletin is available on the IPM website at:
http://www.ipm.msu.edu/pdf/hogweed.pdf

Rebecca Finneran
MSU Extension, Kent County

Michigan ranks as one of the top states for brilliant fall color. Our native maples, oaks and ash provide dazzling displays that can last for up to eight weeks. I am particularly fond of taking note of the sequence of color. I live near a lake and can watch the Tupelo burst into a riot of crimson, followed by sugar maples pealing off multiple shades of harvest orange and finally the oaks that stubbornly bring forth their cinnamon browns. In Kent County, you don’t even have to go up north to take it all in.

Dr. Bert Cregg, MSU Professor of Horticulture and Forestry, says he frequently gets asked the question, “How good will the fall color display be this year?” Last year’s cool, wet fall launched the fall color gurus into false predictions of poor color only to be blown away by the brilliance of it all. Cregg says that no concrete science has gone into the prediction game although there are some horticultural reasons why leaves change color.

Fall is also a time for planting trees, says Cregg. Certain species are noted for their autumn brilliance. To create truly a four-season landscape, he says, you can choose selections that have been tried and true. One of Cregg’s favorites is the Black Tupelo, also known as Nyssa sylvatica. This native species fits into several categories because, unlike many of the other plants we love for fall such as maple, it tends to be a bit smaller. The glossy green leaves are one of the very first to turn a brilliant crimson with shades of burgundy and orange toward the center of the tree. You can find this plant growing along US31 in huge patches between South Haven and Muskegon. It is worth a trip, but get out early to enjoy it, he said.

Another landscape specimen Cregg suggests is the Sweetgum. I would have to agree as I have watched this plant in its native Appalachian habitat as well as in West Michigan turn the most awesome colors that seem to last a long time. The star-shaped leaves and upright habit make this one of the nicest trees for this area. Some gardeners are opposed to the interesting fruits that are noticeable in the winter but are shed abundantly in spring, but who’s perfect? I would give this tree two green thumbs up.

Lastly, Cregg’s unsung hero and a rather late performer is the Scarlet Oak. In the Red oak family, its deep green, glossy foliage turns a perfect crimson just in time for late season football games. Cregg cites some mature specimens on campus as well as an experimental plot in southwestern Michigan that has been performing well and says they are very adaptable for our area. Scarlet oak is somewhat slow growing, but will make a lasting impression for generations to come.

A web site that was launched to help people make smart choices to replace landscape trees can be accessed at: www.hrt.msu.edu/ash.alt where a PDF can be downloaded of tree profiles. You can also call the MSU Extension office to purchase a bulletin entitled, Recommended Alternatives to Ash Trees for Michigan’s Lower Peninsula E-2925.

Fall color guides area available from the U.S. Forest Service as well as a wonderful account of how weather affects the changes and why leaves turn colors. Log on to their website at: www.fs.fed.us/news/fallcolors. You can also call the U.S.F.S. fall color hotline at 1-800-354-4595.

Rebecca Finneran
MSU Extension, Kent County

Rooftops thick with vegetation are getting a lot of press these days. Architects across the nation are carefully considering natural resource conservation, energy saving building techniques, green space revitalization and how to reduce storm water runoff. Many are turning to the age-old technique of incorporating “green roof-tops” into buildings.

But with pressure to develop every corner of the county, a physical sculpting of the land tends to require massive retaining walls and areas of containment. These cement or block retaining walls can be very cold and sterile to the eye and do not help reduce water runoff. A living wall, however, can be a vibrant, earth-friendly solution to the standard retaining wall.

According to David MacKenzie of Hortech in Spring Lake, Michigan, an engineer by the name of Mark Woolbright got an idea while traveling in Europe for a block wall system that looks something like a concrete drawer. Upon his return to his Missouri home, he designed his version and started planting walls all over St. Louis.

The wall block units come in a commercial or “Mega” size and can be designed to accommodate retaining walls that are easily twenty feet high. This 220 pound unit may seem somewhat daunting to the average homeowner, however, so two smaller units are also available. The standard 60 pound unit might be considered mama bear and the “Mite” or 30-pound unit would be the equivalent of baby bear.

Placement of the blocks is easy after reading a few simple directions. The walls can easily be curved and contoured to fit the site, says MacKenzie. The curing process of the block makes them extremely durable. The block systems are competitively priced and even when planted the overall cost is similar to a traditional wall.

As a horticulturist, MacKenzie is most excited about the plants that would go in the wall. He says that walls can be designed with plants that are evergreen or grassy, shade or drought tolerant. There is even a sea wall version of this system. The wall system allows plants to root into the soil out of the back of the drawer, which eliminates the need for irrigation and helps to stabilize the whole system “Just imagine, a wall that has as many four season attributes as your garden,” said MacKenzie.

After studying the walls built in and around St. Louis, MacKenzie noticed the environmental benefit immediately. “Whether psychological or factual, I noticed a 20 degree difference in temperature when standing next to this wall system as compared to a conventional wall,” he said. MacKenzie talked to workers who were ecstatic about looking out their basement window offices at green walls instead of a barren cement wall.

Jeff Andresen
Agricultural Meteorology
Geography

The jet stream will take on a split flow pattern across North America during the next week, with a troughing pattern over the western United States merging with a fast, west to east branch of the flow over the Great Lakes region. This pattern should lead to highly variable weather with frequent chances for precipitation.

In the short term, high pressure will move into the state behind the cool front passed through the state Thursday (September 22), bringing 24 to 48 hours of relatively cool and dry weather. With mostly clear and calm conditions expected overnight Friday in some parts of the state, some scattered light frost is possible in interior northeastern areas of the state where minimum temperatures could fall to the mid-30s. Another frontal system will approach the state by late Saturday and Sunday with the next chance for precipitation. The rainfall will come to an end from west to east across the state by late Sunday, with dry and cool weather expected for the first few days of next work week.

Temperatures during the next couple of days will range from highs in the 60s and 70s on Friday and Saturday to lows from the mid- and upper 30s north to mid-40s south. After a slightly warmer day Sunday, temperatures will fall back to below normal levels Monday and Tuesday of next week with highs generally in the 60s and lows in the 40s.

Medium-range forecast guidance suggests the continuation of an active weather pattern for the Upper Midwest. Precipitation totals for both the 6-10 day and 8-14 day time frames, covering September 28 through October 2 and September 30 through October 6 are forecast at above normal levels. Temperatures during the 6-10 day period are forecast to range from near normal in extreme southern sections of the state to above normal elsewhere, while temperatures during the 8-14 day time frame are expected to return to above normal levels statewide.