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Landscape Alert newsletter

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Vol. 23, No. 4, May 2, 2008

In this issue
Landscape and nursery

Right tree, right place

Scouting for weeds: corn speedwell

Tar spot on maple fungicide timing is now
Turfgrass

Lawn tips to save cash
Christmas trees and forestry

Herbicide-resistant weeds in Michigan Christmas tree plantations

Charcoal of Fraser and Canaan fir

Christmas trees and forestry insect update for May 2

Gypsy moth spray window update May 2
Around the home

Ground nesting bees are scary but harmless

Warm weather brought the ticks out
Polyxenus millipedes

Red squirrel injury to arborvitae

Where did all those winter cutworms go?
Other news

Weather news

Next issue May 9

Right tree, right place
Bert Cregg, Horticulture and Forestry

We’ve all heard the mantra “Right tree, right place.” For many people, however, it’s one of those pieces of advice like “Eat right and get regular exercise” that seems to go in one ear and out the other. None of us can debate the importance of matching tree to site; just like no one can deny that proper diet and exercise are important for our own health. Yet time and time again we run into landscape problems where a few minutes spent on assessing the site and considering which trees are best suited to the conditions would have prevented the trouble before it started. A couple of recent situations I’ve observed set me to thinking about all this. In one case, the problem is fairly minor; the second should make your blood boil if you’re a taxpayer.

In the first situation, a homeowner planted a row of white spruces on the north side of their property as a windbreak. The trees are about 8-10 years old and most are doing fine. The problem is right in the middle of the windbreak is a low spot that holds standing water every spring (Photo 1). Most of the spruces are doing fine but as the soil gets wetter moving toward the low area, the trees get shorter and shorter. At the lowest point, the spruces have finally succumbed after struggling the past couple of years. The situation is difficult since there are few, if any, evergreen conifers that will grow in this situation. Black spruce are among the most flood tolerant evergreen conifers, but not widely planted in the landscape trade. Several deciduous conifers such as baldcypress could tolerate the site, but wouldn’t provide the year round screen that was desired. Constructing a raised berm probably would be the ultimate solution to allow a continuous evergreen screen in this situation.

The second example of “wrong tree-wrong place” is a classic. About 30 eastern white pines were installed as a screen for the rest area along I-96 east of Brighton; never mind that white pine leads nearly every list of salt sensitive trees.

Image 1. Low spot causes standing water in middle of windbreak.

The results were predictable. Every single tree in the planting is dead or wishing it were dead (photo 2 and 3). Assuming a conservative price of $175 per tree installed, that’s at least 5,000 taxpayer dollars gone by the wayside.

The key in both situations is taking time to assess the site before planting. Assessing the site means accounting for the below ground environment (soil pH, soil texture, drainage) as well as the above ground environment (aspect, wind exposure, proximity of utility lines and buildings). Taking a little time before planting to size up the site and then selecting the tree to match the conditions is always easier than dealing with the consequences afterwards.


Image 2. Dead white pine.	Image 3. Dead, salt sensitive white pine on I-96.

Scouting for weeds: corn speedwell
Steven Gower, MSU Diagnostic Services

One of the earliest flowering weeds that homeowners may find infesting their lawns and landscapes this spring is corn speedwell. There are actually several species of speedwell (Veronica) in Michigan. These speedwells are usually very small plants with subtle differences and thus easily confused.

Corn speedwell (Veronica arvensis L.)

Family: Scrophulariaceae (Figwort).

Life cycle: Prostrate, spreading winter annual.

Leaves: Lower and middle leaves are opposite, broadly egg-shaped, hairy, short-stalked with rounded teeth along the margins. Small, narrow, bractlike upper leaves are alternate and without petioles.

Stems: Prostrate and mat-forming, with many branches that spread from the base.

Flowers and fruit: Light blue to violet, inconspicuous flowers are formed in the axils of the upper bract-like leaves on elongated flowering stems. Fruit are hairy, roundly heart-shaped capsules that contain many tiny, yellowish seeds.

Reproduction: Seeds.

Corn speedwell flowering stem.

Corn speedwell plant.

Corn speedwell plants beginning to resume growth in late April in mid Michigan.

Control: Corn speedwell can form dense mats in thin, poor quality turf. As with any lawn weed, understanding and addressing the cultural conditions that promote certain weeds in the landscape will certainly provide more control than any herbicide treatment alone. Generally, improving these cultural conditions in combination with an herbicide treatment can be very effective.

Homeowners have several herbicide options for control of corn speedwell in the lawn. While these herbicides can be very effective, their timing is more important than their application. Corn speedwell can germinate in the fall or very early spring, resume growth in early spring and then flower and set seed in April to May in Michigan. Therefore, herbicide applications in the fall or early spring before the plants produce elongated flowering stems can be very effective.

Herbicides that have good activity on corn speedwell in the lawn include 2,4-D, dicamba, MCPP and MCPA or mixtures of these active ingredients, commonly referred to as “3-way” broadleaf herbicides for turf.

Editor’s note: The identification information is from the new field guide An IPM Pocket Guide for Weed Identification in Nurseries and Landscapes. For ordering information, call 517-353-6740 or visit: http://www.ipm.msu.edu/weeds-nursery/contents.htm

Tar spot on maple fungicide timing is now
Tom Dudek, MSUE educator and Jan Bryne, MSU Diagnostic Services

Nursery tree growers who experienced problems and MDA restrictions last season with tar spot (Rhytisma sp.) leaf infections on maple trees should be targeting fungicide sprays now if "tree appearance" is critical. Apply either triadimefon, mancozeb or Junction at budbreak and at 7-14 day intervals.

Tar spot gets it name from the shiny black, tar-looking lesions it creates on the leaves of several maple species. Several species of Rhytisma cause tar spot. Susceptible maples include Norway, bigleaf, mountain, red, Rocky Mountain, silver and sugar. The maples do vary in their susceptibility to infection.

Tissue is infected in the late spring and early summer after the leaves are fully expanded. Initially, the infected tissue turns light green or yellowish green. At this stage, the disease cannot be easily diagnosed. The pathogen grows slowly in culture; meanwhile more diagnostic symptoms will develop on the host. The diagnostic symptoms include the development of black, shiny, tar-like tissue on the surface of the foliage.

Destroying or fully composting fallen leaves in the fall will help reduce innoculum for the next season in the residential setting. It must be an area-wide effort. A good summary for homeowners’ questions is contained in the Cornell Fact sheet on Tar Spot: http://plantclinic.cornell.edu/FactSheets/tarspot/tarspots.htm

Little, if any research is occurring on this disease especially resistant cultivar trials and the problem is showing up all across the eastern USA.

Lawn tips to save cash
Kevin Frank, Crop and Soil Sciences and Dean Krauskopf, MSUE educator

If you’re like me and keep getting cut-off at the pump by the max credit card charge, you’ve probably also thought about ways to reduce mowing or save money in other ways without compromising lawn quality. Here are some quick tips for maintaining a healthy lawn and saving some cash at the same time.

1. Mow high and follow the 1/3 rule of cutting only 1/3 of the top-growth at any one mowing. If you set the height of cut at 3.5 inches and follow the 1/3 rule, you would not need to mow until the turf reaches 5 ¼-inch height. The growth between mowing is 1 ¾-inch. If you mow at 2 inches and follow the 1/3 rule, you’d only have 1-inch between mowing. Mowing higher is healthier for the turf and should result in fewer mowings, which translates to less gas and less cash out of your pocket.

2. Mower check-up. How often do you change the oil in your car? Do you know where the oil goes in your mower? Tuning up the mower will help improve engine and mower efficiency. Invest a little in a tune-up and you could save a lot in the long-run.

3. Sharpen mower blades frequently. Have you ever had your mower start to “bog down?” One way to improve mower efficiency and improve turfgrass appearance and health is to sharpen mower blades. I try to sharpen my blades at least three times a year to keep the mower humming and turf at its best. Sharper blades will give you better looking and performing turf. Once again you could save some gas and some cash.

4. Return clippings. Mulching blade mowers really do a nice job of chopping up the turfgrass clippings, but even if you don’t have a mulching blade don’t let that stop you from returning clippings. Turfgrass clippings typically contain about 4 percent nitrogen, 0.5 percent phosphorus, and 2 percent potassium. Several researchers have suggested that continually recycling turfgrass clippings to the lawn could reduce nitrogen requirements by up to 25 percent. Don’t believe the hype that clippings contribute to thatch, clippings are about 80 percent water. Unless you’re leaving clippings in piles on the lawn, they won’t build up thatch. Returning clippings is free fertilizer and free definitely saves some cash.

5. Select slow release fertilizers. Select a fertilizer with a high amount of water insoluble nitrogen (WIN on the label) to extend the length of feeding to the turf. Slow release fertilizers will provide steady turf growth as opposed to quick release sources, such as urea, that result in growth surges that cause you to increase mowing frequency.

6. Irrigate when the turf needs it. Anyone that has followed this column throughout the years can recite my irrigation rants, so I’ll spare the repeat. Here’s some thinking points for now. In the last couple weeks, it’s actually turned into a dry spring. You might have noticed the turf isn’t actually surging with growth as lack of soil moisture is probably holding it back. However, the turf is still looking green as cool temperatures are balancing out the lack of moisture and keeping the turf looking good. Take advantage of this strange mix of weather and enjoy the time off the mower. I’m sure rains will come soon enough.

In the meantime if you’re looking for something to do, spend some time checking the distribution and accuracy of the irrigation system. We’ve all seen it too many times when sprinklers are watering sidewalks or even the street.

Herbicide-resistant weeds in Michigan Christmas tree plantations
Steven Gower, MSU Diagnostic Services
Bernard Zandstra, Horticulture

Since the 2004 growing season, several greenhouse experiments have been conducted to evaluate triazine, ALS, glyphosate and PPO resistance in 58 weed samples collected from Michigan Christmas tree plantations. The most popular seedheads submitted were that of common lambsquarters, common ragweed, hoary alyssum, horseweed, Powell amaranth and velvetleaf.

During this screening process, herbicide resistance has been detected in several weeds collected from Christmas tree plantations throughout the state.

Triazine resistance has been detected in:

6 common lambsquarters populations.
2 pigweed populations.
12 horseweed populations.
4 velvetleaf populations.

ALS resistance has been detected in:

1 common ragweed population.
7 horseweed populations.

Both triazine and ALS multiple resistance has been detected in:

1 horseweed population.

Glyphosate resistance has been detected in:

1 horseweed population.

Glyphosate resistance in horseweed was the most recent herbicide resistance confirmed. This population was collected in the spring of 2007 from a Christmas tree plantation in Mason County, Michigan. Michigan is the 16th state in the United States in which glyphosate-resistant horseweed has been confirmed (Heap 2008).

Weed control options for Christmas trees are severely restricted if growers have one or more weeds that are resistant to the triazines (Princep, Aatrex, Karmex), ALS-inhibitors (Oust, Westar) and/or glyphosate. The repeated use of an herbicide without other control methods is the primary cause of development of herbicide resistant biotypes. Practices to reduce the risk of herbicide-resistant weeds in Christmas tree plantations include:

Rotate herbicides with different modes of action.
Use soil-applied, residual herbicides in early spring.
Apply herbicide mixtures.
Scout fields for changes in weed populations or for weeds that escape herbicides that should control them.
Use tillage in combination with herbicides.
Incorporate the use of mulches, ground covers and timely mowing.
Use the recommended rates of herbicides for the appropriate weed height.

Testing for herbicide resistance
If herbicide resistance is suspected in any weed species, samples may be submitted to MSU Diagnostic Services for a resistance screen. Mature, high quality seed or seedheads should be collected from suspicious plants in late summer or fall and submitted in a paper bag or envelope. Do not seal plants or seeds in plastic! Fees associated with herbicide-resistant weed testing are $50 per sample per herbicide site of action (i.e. ACCase inhibitors, ALS inhibitors, Photosynthesis inhibitors). Each additional site of action is $20 per sample. Please contact Steven Gower (517-432-9693, sgower@msu.edu ) with any questions regarding resistance confirmation or sample collection.

Certain weeds, such as horseweed, ragweeds, pigweeds and lambsquarters are more likely to develop resistance than other weeds due to prolific seed production and genetic plasticity/variability.

Charcoal of Fraser and Canaan fir
Dennis Fulbright, Plant Pathology and Jill O’Donnell, Christmas tree ICM educator

A disease that looks very similar to Phytophthora root rot is beginning to be seen more often in Fraser and Canaan fir plantings. We have seen this disease in Michigan for three years now, first on seedling trees, and now on young transplants and mature trees. The nursery stock for the current outbreak was obtained from a nursery outside of Michigan. The symptoms appear to be similar to Phytophthora root rot. The trees appear healthy at first, a few branches turn orange and then the tree collapses with the entire tree turning bright orange. The ends of the branches may take on the appearance of a shephard’s crook as the branches wilt from lack of a functional root system. The main difference between this disease and Phytophthora root rot is this disease manifests itself in a completely opposite orientation in the field. While Phytophthora root rot tends to be found in moist, wet damp soils, charcoal rot is found on dry soils and soils that tend to heat up fast, therefore on dry-slope sandy soils. Charcoal rot intensifies in the hot summer months.

Charcoal root rot is not new to Michigan. It has been found on soybeans in the past, but has not been a common disease in the Great Lakes states. It is known as a disease of regions with warm, temperate and tropical soils, which may say something about climate change. To diagnose, take dead roots and remove the outside roughened bark.

Scan the white cylinder of the root (small or large roots) with a hand lens looking for black, pepper-like dots. These are the sclerotia, or long-term survival structures of the pathogen named Marcophomina phaseolina. The dead trees will have the black sclerotia, and the living trees may also have them, but not as severe. These sclerotia will be responsible for new infections in the field if replanted to a susceptible species. The species name indicates it attacks beans, but this pathogen has over 300 hosts, including weeds, and will infect and kill Fraser fir, Canaan fir, Douglas fir, other firs, many pines and Engelmann spruce.

If you think you have seen this disease on your farm or nursery, please call Dennis Fulbright at 517-353-4506 or Jill O’Donnell at 231-779-9480.

Christmas trees and forestry insect update for May 2
Jill O’Donnell
Christmas Tree ICM educator

Spruce needleminer
Scouting blue spruce this past week, it seems we are seeing an increase in the numbers of spruce needleminers. Right now you will find the larvae webbed into nests of hollowed-out needles. These immature larvae over-wintered in these nest and will feed for a few weeks and then pupate. Adults begin to emerge in mid-June and lay eggs on the needles. In about two weeks, larvae hatch and begin mining needles. Even though the larvae are present now, they are pretty protected in the webbed nests. Timing to control this insect will be to control the larvae just after they emerge from the eggs, in late June to mid-July.

European pine sawfly
Growers should begin to scout for egg hatch of European pine sawfly (between 100 and 195 GDD50). This insect rarely builds to high enough levels to significantly damage the health of trees, but we have seen some pockets in past years with large numbers of sawfly larvae causing severe defoliation. Often growers don’t realize they have a problem until they see the trees turn brown from the larval feeding. Make sure to walk through your fields. Scouting through the windshield you can mistake this browning

Spruce needleminer larva in webbed nest.

browning for Lophodermium needlecast on Scotch pine. If you see small numbers of these little green larvae on your pine tree, just clip out the colony. Lots of predators and parasitoids like to attack sawfly larvae too.

Balsam twig aphid
In the northern half of the Lower Peninsula, scouting balsam fir this week we found balsam fir stem mothers present. The ideal time to spray is at 100 to 140 GDD50 after the stem mothers have hatched, but before the sexuparae (second generation) aphids are present. Typically at this point, buds are swelling but have not yet broken. If you had heavy damage from this aphid in your Fraser or balsam fir fields last summer, now is the time to apply an insecticide. The aphids are stem mothers and are maturing quickly. Only use an insecticide if your trees had significant damage last year. There are a variety of predators that attack these aphids, plus the trees outgrow at least 50 percent of the damage by fall. In addition, research that we conducted during the last two years indicates that customers at choose-and-cut Christmas tree farms don't even notice balsam twig aphid damage unless it is very, very heavy (e.g. more than 60 percent of the shoots are affected).

White pine weevil and Zimmerman pine shoot moth
In the Upper Peninsula it’s time to control those early insects such as white pine weevil and Zimmerman pine shoot moth. Larvae of the white pine weevil kill the terminal leader and the top two to four years of growth on many varieties of spruce, as well as white and Scotch pine trees. If you had weevil damage last year and you need to control the weevils, you will have to do it early this spring. The adult weevils overwinter on the ground, protected and insulated by the litter (fallen needles). Once they warm up, the weevils move up to the tops of the trees in the late afternoon or early evening and feed on the terminal leader. Each time a female weevil makes a feeding wound on the terminal, she lays one to four eggs in the wound. Those eggs will hatch within a few weeks and the larvae chew their way through the bark. They will feed in the phloem under the bark for several weeks, pupate and then emerge as new adults around mid-summer.

If you need to control white pine weevil, your one opportunity is early in the spring. Insecticide should be applied to the terminal leader once it begins to warm up somewhere around 25-65 GDD50. It's better to be a bit early than to be late with this application. Use a persistent product, because the adult weevils don't all warm up at the same rate.

Zimmerman pine moth is another early season pest of Scotch pine and it will often infest Austrian pine as well. The tiny caterpillars are currently on the bark of the stem and branches, well protected in a silk shelter. Once they get warmed up, they will start to chew under the bark. After they get under the bark, they will be well protected for the rest of their life cycle. Therefore, if you plan to use an insecticide to control Zimmerman pine moth, it needs to be applied early, around 25-50 GDD50. Again, use a persistent product and make sure to increase your amount of water per acre to get good coverage on the trunk of the tree.

When our articles include references to growing degree days (base 50 degrees F), we are hotlinking them to maps that indicate the average calendar dates when regions surrounding the Great Lakes reach that particular accumulation of degree days. This information is to aid your planning and must be cross-checked with the current degree day accumulations in your area to reflect current season conditions. MSU’s Enviro-weather offers daily degree day accumulations at 52 sites in Michigan. Efforts are underway to expand station coverage into new regions of the state. – Joy Landis, editor.

Gypsy moth spray window update May 2
Mike Bryan, MDA

Growers should note that the spray window open date have been set for Zones 1 and 2 - all compounds for Tuesday, May 6. The spray window open date for Zone 3 – Dimilin has been set for Tuesday, May 6. The spray window open date for Zone 4 – Dimilin has been set for Saturday, May 10. Spruce, fir and Douglas-fir nursery stock being shipped to destinations outside the gypsy moth regulated area requires a new treatment once the spray window is open. The reason is that gypsy moth hatch is imminent and nursery stock is at risk for infestation by larvae “ballooning” on their silk. Those who ship nursery stock outside the regulated area should consult with MDA staff for obtaining certification to meet the USDA Gypsy Moth Quarantine.

The accompanying chart shows actual and projected open/close dates for application of the two groups of pesticides used for regulatory treatment of gypsy moth in nursery stock and Christmas trees. We are listing the projected dates as guidelines to help you plan your pest management program. Since gypsy moth development will vary by location, you will need to monitor development around your farm. Weather conditions will affect caterpillar development and may effect end date of the spray windows. Growers should watch the Landscape Alerts for additional announcements.

Zone	*Open – Dimilin (150 DD)**	Open – all other compounds (200 DD)	Close – Dimilin (700 DD)	Close – all other compounds (800 DD)
1	May 1	May 6	June 9 (projected)	June 15 (projected)
2	May 1	May 6	June 15 (projected)	June 20 (projected)
3	May 6	May 15 (projected)	June 21 (projected)	June 27 (projected)
4	May 10	May 21 (projected)	June 28 (projected)	July 4 (projected)
5	May 20 (projected)	May 27 (projected)	July 3 (projected)	July 11 (projected)

* DD = Degree days at base 50ºF.
Note: Projections are based on 30-year historical degree day data.
Zone map : A list of counties comprising each zone and a statewide zone map appeared in the April 18, 2008 edition of the Landscape Alert.

Ground nesting bees are scary but harmless
Howard Russell, MSU Diagnostic Services

Many people have called the lab recently to complain about large congregations of ground nesting bees in their yards. There are many common species of solitary bees that nest in the ground. Most of these belong to families Colletidae, Andrenidae and Halictidae. Those that terrorize us early in the spring are most likely andrenid bees. Unlike a colony of yellowjackets that use a single nest entrance and work together to raise their brood, each of these female bees construct individual nest tubes, each with its own opening. Even though large numbers of solitary bees often nest together, they do not cooperate or help each other raise their young, they just seem to enjoy each others company. Solitary bees are not aggressive and rarely sting, and there is no mass attack as might be found with honeybees and yellowjackets. People can mow over their nests and garden in close proximity to them with little worry of being stung.

Beginning in April or early May, females dig out their nesting tubes during the evening hours. These may reach six or more inches in depth. Tubes are lined with a secretion
that protects the nest from moisture. Small mounds of soil may appear around each nest opening. During the day, the active females collect pollen and nectar to provision their nests. They lay a single egg on the collected pollen. After hatching, the larva feeds on the pollen and develops within the tube until it reaches adulthood in the fall. The new adult remains in the borrow until the following spring. At this time, mating takes place and bee activity begins to pick up as the nesting cycle resumes. Though adult bees

An adrenid bee nest opening. Adrenids are one type of solitary ground nesting bee that folks are seeing in large numbers in their yards this spring. Photo credit: W. Cranshaw, Colorado State University. Courtesy of Forestryimages.org

feed on nectar, none store honey. Their nesting behavior usually lasts for four to six weeks. Ground nesting bees play a vital role in ecological systems, especially in pollination of crops and wild plants, and they should be preserved whenever possible.

Ground nesting bees generally prefer to nest in areas with morning sun exposure and well- drained soils containing little organic matter. Tunnels are excavated in areas of bare ground or sparse vegetation and damp soils are avoided. Damage to lawns and turf is usually minimal and control is often sought because the bees are perceived as a danger or annoyance.

Controlling solitary bees in yards is best accomplished by cultural control methods. The best cultural control method is to establish dense turf in the area(s) that the bees favor. Heavy watering or irrigation with a lawn sprinkler during the nest-building period may also help to discourage nesting behavior. If the soil or location is not conducive to a healthy, dense lawn, then using ground covers or heavy mulches may be an alternative solution. Mulches may be used on bare patches caused by heavy traffic where grass will not grow. I do not recommend control with insecticides because the bees are at worse a minor and temporary annoyance

Warm weather brought the ticks out
Howard Russell, MSU Diagnostic Services

Our recent warm snap fired up the dog ticks. We had several people send us American dog ticks last week during our first real warm weather of the year. Many more called the lab to report tick activity in their area. American dog ticks, Dermacentor variabilis, can readily be distinguished from other tick species by their white markings on their backs. These markings appear differently on females and males. The American dog tick is the most commonly found tick in Michigan. Dog tick bites rarely result in serious disease in Michigan, but like other wood ticks, the dog tick is a known carrier of Rocky Mountain spotted fever and tularemia.

The cases of Rocky Mountain spotted fever reported in Michigan have been from primarily southern counties, particularly those located directly north of the Toledo Airport. Also, toxins injected with their bites cause itching, fever and in some cases tick paralysis. Be on alert for any rash or fever, which is a primary symptom of both Rocky Mountain spotted fever and tularemia that develops after a tick bite. Keep in mind that a tick requires several hours to puncture our skin in order to take a blood meal as they do not have the cutting mechanism on their mouthparts like that of a mosquito.

American dog ticks: a female dog tick (left) and a male dog tick (right). Photo credit: H. Russell, Diagnostic Services.

Ticks have to ram their mouthparts through our skin. The best method for removing an attached tick is to use a pair of tweezers to grab the tick by the head and pull it out. It is never a good idea to remove a tick by grabbing it with your thumb and index finger. This will turn the tick into a hypodermic needle that will inject the internal contents of the tick into the wound when it is squeezed.

These ticks are most likely to be encountered in the spring and early summer along animal paths in grassy, shrubby areas adjacent to woodlots and forests. Family members and pets should be inspected daily where ticks are known to be abundant. Insect repellents may help keep wood ticks from biting. Permethrin tick repellents can be applied to clothing to discourage ticks from climbing aboard. Yard borders can be sprayed with permethrin or Sevin to help reduce the number of ticks in yards.

Polyxenus millipedes
Howard Russell, MSU Diagnostic Services

Last week a lady brought in some strange little creatures she found crawling on her basement walls. It was quite obvious that she was very annoyed with these little intruders. With a quick look through the scope, I was able to tell her that her bugs were adorable little Polyxenus millipedes, also known as duff millipedes. She didn’t want to hear about adorable. She didn’t want to hear about them being a rare find. She didn’t want to hear about them being incidental and temporary. She didn’t want to hear about them drying up and dying on their own. She wanted them dead and she wanted them dead immediately. She wanted a name of an insecticide that would kill them. Yes, ma’am. Right away, ma’am.

Polyxenus millipedes are strange little critters that look more like carpet beetle larvae than they do millipedes, but if one looks closely, they are definitely millipedes. They have two pairs of jointed legs on each body segment whereas carpet beetle larvae have a single pair of legs on just the first three segments behind the head. Their minute size (2-3mm), soft integument (skin), and the presence of rows of serrated setae (hairs) on their backs and sides, and long posterior tufts of setae characterize Polyxenus millipedes.

A cute little Polyxenus millipede on a penny. Photo credit: H. Russell, Diagnostic Services.

It is reported that polyxenid millipedes may occur in pine litter in great numbers. Like other millipedes in Michigan, Polyxenus feed on both living and dead plant materials. There are only six species in North America.

When found indoors, Polyxenus should be assumed to be coming from outside the building as indoor humidity levels would seem to be too dry to support the development of any millipede. I told the lady that perimeter treatments around the outside of the building with any number of insecticides should reduce the numbers found inside her home. Then she left. She left in a huff.

There are more than 10,000 described species of millipedes worldwide. These species are organized into 1,700 genera, 115 families and 15 orders. Most millipedes are worm-like with over 20 body segments. Each body segment, except for the first several segments behind the head bears two pairs of legs. In many species, the body segments contain internal glands that secrete volatile chemicals that repel or discourage predators.


A carpet beetle larva for comparison. Photo credit: H. Russell, Diagnostic Services.	A close up of a Polyxenus millipede showing the tufts of hairs that might cause it to be mis-identified as a carpet beetle larva. Photo credit: H. Russell, Diagnostic Services.	A close up of the typical millipedes legs. There two pairs per segment. Photo credit: H. Russell, Diagnostic Services.	This is the type of millipede that is typically submitted to the lab. Photo credit: H. Russell, Diagnostic Services.

Red squirrel injury to arborvitae
Howard Russell, MSU Diagnostic Services

Last week a gentleman brought in a small arborvitae that he thought had died over the winter. He brought in the whole shrub, roots and all. A quick examination of the shrub told us that it was not dead. The branches were not brittle and many of the lateral buds had broken and new growth was appearing all over the shrub. But something had stripped all the foliage off of this shrub. As well as three more that were still in the ground back home in the client’s yard. We immediately thought deer were responsible because deer really like to munch on arborvitae during the winter months. But when the client told us these arborvitae were in an area of his yard that was pretty much inaccessible to deer and that all of the stripped off foliage was piled up at the bottom of the shrubs, we had to nix the deer theory. Deer would not leave the foliage, they would have eaten it.

The only thing we could think of was red squirrels (see the April 18 issue Landscape Alert). I could not find any reference that mentioned red squirrels feeding on arborvitae, but the MO is so similar to that of spruce, this remains our best guess. If you have a better one, email me at bugman@msu.edu.


A close up of an arborvitae branch pruned off by what we think was a red squirrel. Photo credit: H. Russell, Diagnostic Services.	A photo of the arborvitae shrub that was brought into the lab that was nearly completely defoliated by what we think was a red squirrel. Photo credit: S. Gower, Diagnostic Services.

Where did all those winter cutworms go?
Howard Russell, MSU Diagnostic Services

In the first issue of the 2008 Landscape Alerts, Chris DiFonzo and I documented a widespread outbreak of winter cutworms that occurred last fall in many northern counties of the Lower Peninsula. We expected to hear more about these guys this spring, but alas we have not. Were did they go and what happened to them all?

Jill O’Donnell may have come across a possible answer: they all climbed up a spruce tree and died. Jill found hundreds in various states of near death and decomposition up in spruce trees when she scouted a Christmas tree plantation this week. Maybe winter cutworms are like elephants and Jill discovered their secret burial grounds. The mystery continues.


A long-dead winter cutworm in a spruce tree. Photo credit: J. O’Donnell, Wexford MSU/E.	A dying winter cutworm in a spruce tree. Photo credit: J. O’Donnell, Wexford MSU/E.

Weather news
Jeff Andresen
Agricultural Meteorology
Geography

An area of low pressure over the central Great Plains on Friday, May 2, is expected to move northeastward through the Great Lakes region during the next few days, bringing a period of unsettled weather to the region. Showers and thunderstorms will be possible statewide Friday through Saturday. Some severe thunderstorms are possible across southern and central sections of the state late Friday into early Saturday, especially if there are more breaks in the cloud cover Friday than expected (i.e. more sunshine). A cold front moving through the state Saturday will gradually bring an end to the precipitation from west to east by early Sunday. Precipitation totals through Sunday should generally range in the 0.5-1-inch range in most areas of the state, with some isolated 2-inch totals possible. Fair and drier weather is expected again by next late Sunday continuing into the middle of next week.

Another area of low pressure will approach the region once again by Wednesday or Thursday of next week with the next chance for significant precipitation. High temperatures will range from the low-mid 40's north to upper 60's south Saturday, falling back to the 40's north to upper 50's south Sunday. Low temperatures will range from the upper 30's north to mid-50's south Saturday morning falling back to the low or mid-30's north to the upper 30's south by Monday. Some scattered light frost is possible across inland northern sections of the state through the middle of next week.

Further ahead, medium‑range forecast guidance suggests a series of upper air troughs moving from the western United States eastward into the Midwest, with an active storm track across the Great Lakes region. Both 6-10 day and 8-14 day outlooks covering May 7-11 and May 9-15 call for below normal mean temperatures and near to above normal precipitation totals statewide. Due to some disagreement among the models used in the development of the outlooks, forecaster confidence is considered lower than normal.

The MSU IPM Program maintains this site as an access point to pest management information at MSU. The IPM Program is administered within the Department of Entomology, fueled by research from the Michigan Agricultural Experiment Station, delivered to citizens through MSU Extension, and proud to be a part of Project GREEEN.
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