Landscape and nursery
§ Update on garlic mustard biological control
§ Cone season begins
§ Should I boycott cypress mulch?
§ Scouting for diseases: Sclerotinia
Turfgrass
§ Frost and grass sawfly
§ European chafer found the in the Upper Peninsula
§ Scouting for weeds: black medic, birdsfoot trefoil and yellow woodsorrel
Christmas trees and forestry
§ Armillaria root rot
§ Christmas tree and forestry pest update
§ Gypsy moth spray window dates
Around the home
§ Clover mites are swarming in and on homes
§ Insect (and spider) update from Diagnostic Services
Other news
§ Turn vacant lots into food and profit
§ Weather news
Jeffrey Evans and Doug Landis, Entomology
Garlic mustard is a biennial invasive weed native to Europe
that is now widely distributed across North America from
Ongoing research has shown that garlic mustard seeds can
remain viable in the soil for at least ten years. Thus, long term management by
hand is impossible for all but the smallest infestations. A search for suitable biological control agents for garlic
mustard was initiated in 1998 by MSU collaborators at
Larvae of
these species mine inside the root crowns of overwintering
rosettes (Ceutorhynchus scrobicollis),
mine in garlic mustard stems and leaf petioles (C. alliariae, and C. roberti), or feed on developing garlic
mustard seeds (C. constrictus).
Adults of all four species feed on garlic mustard foliage, which further
reduces seed production. Population modeling studies by MSU researchers Adam
Davis (now with USDA ARS in Illinois), Doug Landis and Doug Schemske
suggest that releasing the root crown miner either alone or in combination with
one of the stem-mining species is likely to be the most effective strategy for
the greatest number of invaded sites. Current work in our lab is focusing on
refining these models with new data we are collecting from
Before weed biological control
agents can be released, researchers must evaluate the breadth of their feeding
preferences to demonstrate that they won’t harm non-target plant species. This
host specificity testing has been completed for the root crown miner, and a
proposal to conduct test releases is currently being prepared for the federal
Technical Advisory Group, which oversees weed biocontrol.
Testing is continuing on the other three candidate agents in
For more information on garlic
mustard invasions and control in
The goal of management is to prevent garlic mustard from producing new seeds. Most first year seedlings and rosettes will die naturally, so management efforts should be focused on second year plants. Second year plants are easy to distinguish from first year rosettes in late spring once their stems elongate in May and they begin producing white flowers. First year rosettes will not have long stems or flowers and lay close to the ground. In summary, small infestations can be managed with vigilant pulling of second year plants every year prior to seed production or with careful application of glyphosate (e.g. Roundup) during the late fall or winter when most native species are dormant.
We now know that viable seeds can develop on any garlic
mustard plants that have already flowered, even after the plants have been
pulled. For this reason, we no longer recommend burying pulled plants. Plants
should be bagged in plastic, tied up, and removed.
Bert Cregg
Horticulture and Forestry
We are beginning to receive reports of cones developing in Fraser fir Christmas tree plantations. So far, the indications are the crop is variable, with relatively few cones in some areas and fairly heavy cones in others. Firs are known to exhibit a biennial pattern of cone production. That is, heavy cone crops alternate with light cone crops. The physiological explanation is based on source-sink relations. In heavy cone years, trees allocate their resources to the current year’s cone production, and therefore have less remaining energy to put into new shoot growth and buds for the following year.
Based on this, some
alert readers may be asking, “Since we had exceptionally heavy coning last
year, shouldn’t there be few cones this year?” Part of the answer is that
growers usually “short-circuit” the alternate-bearing cycle by picking cones
when they are small, and before they become a major drain on the tree’s
resources. We will likely see evidence of this if we look at conifers in the
landscape, which had heavy cones last year, but were not picked. The other part
of the answer is that environmental signals can still override the internal
signals within the tree. High temperatures, drought stress and high levels of
nutrition promote cone formation the following year. In 2005, June in
Bert Cregg
Horticulture and Forestry
It’s hard to think of mulch as a controversial topic, but as
with most things these days, we find people on both sides of an issue. As with
most things these days, some of the opinions are based on substance, others are
not. In the southern
“Many of our
cypress-tupelo forests are in a severe state of decline. As you can imagine,
these forests are very important to south
The inability to regenerate new stands of cypress is an important concern and calls into question the sustainability of cypress harvesting on these sites. Chambers is working with environmental groups and others to develop a process to certify that mulch is produced from sustainable forest harvest operations.
Another issue related to cypress mulch, is a claim that is
circulating in parts of
Jan Byrne
Diagnostic Services
Pathogen: Sclerotinia sclerotiorum.
Hosts Include: Anemone, Aquilegia, Aster, Bellis, Campanula, Coreopsis, Delphinium, Digitalis, Helianthus, Hosta, Iris, Liatris, Lupinus, Papaver, Platycodon, Rudbeckia and Scabiosa.
Symptoms: Pre- and postemergent
damping-off, crown rot, and blighting of foliage and petioles. Small, hard,
irregular, black structures called sclerotia may be
present on or in plant tissue (especially inside stem and petiole tissue).
White, fluffy growth on affected plant parts is most readily visible in high
humidity.
Spread: Sclerotia, long-term survival structures, are found in soil and on plant debris. The disease is primarily spread when these structures are moved. Disease can also be spread when infected plant material is moved.Under certain environmental conditions, mushroomlike structures (apothecia) are produced. These release air- borne spores.
Management: Field soil should be sterilized before
use in growing media. Susceptible crops should not be grown in areas with a
history of white mold problems. Additionally, good sanitation is important to
limit spread. Control weeds in production areas – some weeds are hosts to
S. sclerotiorum. Fungicide drenches can protect
plants from infection.
Kevin Frank
Crop & Soil Sciences
After the heavy frost across many areas of
Grass sawfly is making a repeat engagement in the
Howard Russell
Diagnostic Services
Jim Isleib, MSUE director in
Steven Gower
Diagnostic Services
The yellow-flowered, compound-leafed weeds will be blooming in our lawns very soon. The culprits include black medic, birdsfoot trefoil and yellow woodsorrel. These weeds all have small yellow flowers and compound leaves. Just as with any other pest, identification of these yellow-flowered weeds is important to understanding why they are in the lawn. Is the site low in nitrogen? Is the site drought stressed? Are you mowing too low? These could be just a few reasons why black medic, birdsfoot trefoil and yellow woodsorrel are thriving in the lawn.
Understanding and addressing the cultural conditions that promote certain weeds in the landscape, will certainly provide more control than any herbicide treatment alone. Improving these cultural conditions in combination with an herbicide treatment can be very effective. Herbicides that have good activity on black medic, birdsfoot trefoil and yellow woodsorrel in the lawn include 2,4-D, dicamba, triclopyr, clopyralid or mixtures of these active ingredients.
Black medic: (Medicago lupulina L.)
Family: Fabaceae (Legume)
Life cycle: Prostrate, trailing summer annual.
Leaves: Alternate, compound – with three oval to egg-shaped leaflets – hairless to sparsely hairy, shallowly toothed along the upper half and tipped with a small point. The central leaflet is found on a definite stalk; the two lateral leaflets are nearly stalkless. A pair of stipules is present at the base of each petiole.
Stems: Prostrate,
trailing to ascending stems are wiry, usually hairy, multibranched
from the base and up to 2 feet long.
Flowers and fruit: Numerous, very small, yellow flowers are formed in dense, mostly globe-shaped, cloverlike clusters. Fruit are clusters of black, coiled, kidney- to bean-shaped, one-seeded pods.
Reproduction: Seeds.
Birdsfoot trefoil: (Lotus corniculatus L.)
Family: Fabaceae (Legume)
Life cycle: Mat-forming
perennial.
Leaves: Alternate,
compound with five generally oval and smooth-margined leaflets. Each compound
leaf has three terminal leaflets and two reduced leaflets near the stem.
Stems: Prostrate and spreading to semierect stems are herbaceous, branched from a tough crown and up to 3 feet long. Plants form mats by stolons and rhizomes.
Flowers and fruit: Bright
yellow, pealike flowers, sometimes streaked with red,
are found in flat-topped clusters at the ends of long stalks. Fruit are several
linear, cylinder-shaped pods formed in the shape of a bird’s foot. Each capsule
contains several roundish, shiny, olive
to black seeds.
Reproduction: Seeds, stolons and rhizomes.
Yellow woodsorrel: (Oxalis stricta L.)
Family: Oxalidaceae (Woodsorrel)
Life cycle: Low-growing
annual or simple perennial.
Leaves: Cotyledons
are rounded to oblong. Gray-green leaves are alternate, compound and cloverlike, with three heart-shaped leaflets that attach at
the pointed ends. Long-stalked leaves have smooth surfaces, but they are
fringed with hair along the margins.
Stems: Low-growing,
prostrate to erect stems with minimal branching at the base, up to 20 inches
tall. Plants spread by long, slender rhizomes.
Flowers and fruit: Yellow
flowers with five petals are found in long-stalked clusters. Fruit are ridged,
hairy, cylinder-shaped capsules with pointed tips that range from 0.5 to 1 inch
in length. The capsules explosively eject small seeds with a sticky coating up
to several feet away. Seeds are mostly brown, ridged, oval and flattened.
Reproduction:Seeds
and rhizomes.
Note: Identification information for more weeds is available in the new field guide An IPM Pocket Guide for Weed Identification in Nurseries and Landscapes. To order, call 517-353-6740 or visit: http://www.ipm.msu.edu/pdf/pocketGuidesLandsc07.pdf
Jill O’Donnell
Christmas Tree ICM educator
This past week, I visited a field of small
Armillaria root rot can be caused by several species of Armillaria, and for diagnosis and management, knowing the species is not that critical. This fungal pathogen attacks several hundred woody species, as well as some herbaceous plants. It is particularly common to forested areas or areas that had been forested. Armillaria exists most of its life as a saprophyte, but it can infect trees that are weakened by stresses. Sometimes it can even infect healthy trees, which are killed outright or are weakened, leaving them vulnerable to other pathogens or environmental stresses.
Armillaria produces rhizomorphs, which grow under the bark of dead or dying trees and stumps. In at least one circumstance last year, we were able to trace the rhizomorphs from the dead trees in the plantation to the dead stump of the previous fir crop. Rhizomorphs can grow up to 60 feet advancing less than 10 feet per year. When a rhizomorph comes into contact with a root of a host species, the fungal mycelium adheres to and then penetrates the root by secreting digestive enzymes. The fungus is then able to grow through the root and subsequently up into the trunk. Armillaria can also spread from tree to tree through root grafts.
The rhizomorphs may also give rise to the sexual mushroom stage, particularly after wet periods during the fall. These mushrooms release spores that may infect the trees; however, it is unlikely that these spores play a prominent role in the disease cycle.
Infected trees exhibit symptoms similar to other root diseases. In otherwise healthy trees, crown symptoms may take several years to develop and may be accompanied by branch and shoot dieback and premature foliage loss. However, in weakened trees, foliage may rapidly turn color with tree death occurring soon after.
Because Armillaria is a natural component of the forest ecosystem, it is not possible to try to eradicate the fungus. The best way to control the disease is to prevent trees from becoming stressed. Remove dead trees and the stumps from previous plantings. Avoid planting into cut over sites, especially those with hardwood stumps. In areas where Armillaria has been a problem, do not continue to plant susceptible trees, such as balsam or Fraser fir. Keep trees as healthy and as vigorous as possible.
Jill O’Donnell
Christmas Tree ICM educator
The freezing temperatures that occurred this past week resulted in frost damage to Douglas-fir, spruce, balsam, corkbark and concolor firs. (view images) Since most of these species had broken bud by that point, the freeze resulted in textbook examples of late frost damage. This damage is characterized by browning or wilting of new shoot growth. While frost damage looks severe when it first occurs, most trees are able to recover. Some trees might need some corrective pruning if damage is especially severe.
Just a reminder, if you have pine fields enrolled in the Compliance Program, you need to collect and destroy all trap logs or trap trees by May 20. Be sure you chip or burn trap logs and trap trees, as well as any other pine brood material you might have generated over the last several months.
New galls usually appear around 200-300 degree days base 50. Once the new galls are present, insecticides will not be effective.
If you had lots of distorted needles from Cooley adelgids on your Douglas-fir trees last summer, you need to be keeping an eye on your trees. Look for the dark-colored nymphs on the new needles. Once buds break, the adelgid eggs will hatch and the nymphs move down to feed on the soft, succulent needles as they expand. These nymphs will be exposed at the ends of the shoots and will not be protected by the little white waxy fibers they secrete. If you need to use an insecticide, this will be the best time to apply it.
If you have Scotch pine trees that had high densities of pine needle scale last year and your fields are in southwest or southeastern lower Michigan, you need to be scouting your trees right about now. The first generation of eggs will usually hatch around 300 degree days base 50. It's not necessary to apply an insecticide immediately after you see the reddish-colored crawlers. In fact, it's best to let the crawlers settle down and establish feeding sites on the needles( the hyaline stage – 400-500 GDD Base 50). At this point, the immature scales are exposed and have not yet secreted the white, waxy protective armor. If you can apply your spray at this point and if you get good coverage, you should get good control.
Keep in mind that pretty much any registered, contact insecticide will be effective on pine needle scale. You do not need to use a systemic product. This scale feeds on sap from the parenchyma cells in the needle, and systemic insecticides are not going to be more effective than contact insecticides. (In contrast, pine tortoise scale feeds on phloem sap, and systemics are likely to be more effective than contact insecticides).
Spruce needleminer
On several samples of spruce that came into the office, I found spruce needleminer larvae webbed into nests of hollowed-out needles. These larvae will feed for a few weeks and then pupate. Adults begin to emerge in mid-June and lay eggs on the needles. 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.
Pine root collar weevils
Pine root collar weevil larvae girdle the root collar and roots of Scotch, Austrian, red and eastern white pine. This feeding can weaken and kill trees. Trees attacked by this weevil may fall over and die one to four years after being attacked.
Weevils require two years to complete their entire life cycle. Adult weevils lay eggs at the base of pine trees. Each female adult will lay 10 to 70 eggs in one season. Eggs hatch in seven to 17 days, depending on temperature. Larvae are small (up to 1cm long), whitish grubs. Larvae burrow into the inner bark (cambium) of the root collar and large roots, and feed until the weather turns cold in autumn. During the winter, larvae are inactive and are protected from cold temperatures in galleries under the bark or in tunnels in the soil. As the soil warms in the spring, larvae resume feeding. Pupation occurs in chip cocoons made of sawdustlike frass. They are found in the soil near the root collar or, occasionally, under the bark. Adult weevils emerge in 30 to 40 days.
Adult weevils should be emerging in the southern part of the
European pine sawfly
Sawfly eggs hatch 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 for Lophodermium needlecast on Scotch pine. If you see small numbers of this little green larvae on your pine tree, just clip out the colony. Lots of predators and parasitoids like to attack sawfly larvae too.
Douglas-fir needle midge
Douglas-fir needle midge is a relatively new pest to
Mike Bryan
Michigan Dept. of Agriculture
Growers should note that spray window open dates have now been set for Zone 4 - all compounds and Zone 5 - Dimilin. The following updated 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. 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 CAT 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 |
April 23 |
May 4 |
June 9 (projected) ** |
June 15 (projected) |
|
2 |
April 30 |
May 7 |
June 15 (projected) |
June 20 (projected) |
|
3 |
May 3 |
May 15 |
June 21 (projected) |
June 27 (projected) |
|
4 |
May 15 |
May 21 |
June 28 (projected) |
July 4 (projected) |
|
5 |
May 18 |
May 27 (projected) |
July 3 (projected) |
July 11 (projected) |
* DD = Degree Days at base 50 degrees F.
** Projections are based on 30 year historical degree day data.
The 2007 Bug season is in full swing!
Howard Russell
Diagnostic Services
Several folks sent in to Diagnostic Services, clover mites, Bryobia praetiosa (Acarina: Tetranychidae) that they
found by the hundreds or thousands on the outside of their homes. (view photo) Many had found their way inside, as well. Clover
mites are among the smallest home invaders we have in
Clover mites are usually a temporary nuisance. They appear suddenly and are generally gone a few days later. Household aerosol insecticides can be used to kill the mites indoors, if deemed necessary, but a soapy rag or wet sponge work just as well on indoor surfaces. A vacuum cleaner equipped with a hose and a soft brush attachment will also work. Wipe or brush carefully to avoid crushing the mites and causing stains. Mites can be removed from the outside of buildings with a garden hose. An insecticidal soap can be concocted by using regular liquid dish-washing soap mixed at the rate of 2 tablespoons per gallon of water. These water-based treatments will not provide any residual control. A more aggressive approach, would be a perimeter treatment of a persistent insecticide along the outside walls and extending about 10 feet out from the foundation.
The best long-term method for reducing persistent clover mite invasions, is by providing a grass-free band, 18-24 inches wide, around the house. This can easily be accomplished by open areas of course sand or pea stone, or by installing a plant bed. Removing clovers and other groundcovers from the lawn, may also help prevent mite numbers from building up in lawns.
Howard Russell
Diagnostic Services
Paper wasps, Polistes sp., are well into their nest building activities. (view photos) I observed both the European paper wasp, P. dominulus and our native paper wasp, P. fuscatus, on their small newly constructed nests this past week. The European paper wasp is far less selective about where they build their nests. Almost any site that offers the slightest protection from the rain will work for P. dominulus. Inside bird feeders, under or in mailboxes, inside the various nooks and crannies found in parked cars, are among their favorite nesting sites. Controlling paper wasps early in the season is much easier than in August, when the wasps are far less tolerant of those that venture close to their nests.
Last Friday evening as I enjoyed my post work beverage of
choice, I watched two spiders fight it out in the window of my shop, which my wife
occasionally refers to as ”her garage” (Silly!). One
of the spiders involved was a big ol’ black jumping
spider, known commonly as the Bold Jumping spider, and scientifically as Phidippus audax (Araneae: Salticidae). P. audax is
one of the most commonly encountered and (apparently feared) spiders
Jumping spiders are said to be the smartest of all the spiders. They do not spin webs, but rather use their smarts and keen vision to stalk and subdue their prey. My money was on the much larger and more robust Phidippus. I soon learned that I (and Phidippus) had underestimated the power of spider silk. I watched Phidippus move around the edges of the theridiid’s web trying to gain an advantage. After a brief sparing match, the theridiid moved to the center of her web and calmly waited for the Bold Jumper to make her move. The end came quickly for the overly aggressive Phidippus. When she climbed on the web to attack, the theridiid simply out maneuvered her, and surrounded her with strands of silk until Phidippus was trapped. As Phidippus struggled, the theridiid bit and envenomated one of her long front legs she had extended. As the venom did its work, Phidippus quieted, and the theridiid pressed her attack and bit several other of the jumping spider’s legs. When Phidippus stopped moving, the theriviid quickly trussed up her prize in tight wrapping of silk. The fight was over, and the feast was about to begin. I couldn’t help but think about just how geeky I had become.
In closing, I would like to mention a couple of other bugs that came into the lab this past week. Fishflies, Chauldes sp. (Megaloptera: Corydalidae) are out and about. These large and primitive looking aquatic insects are attracted to lights and are commonly found on outside walls of buildings that are near ponds and slow moving streams. See photos of fishflies at: http://bugguide.net/node/view/3610. I also received specimens of male wood roaches, Parcoblatta sp., that a client found in his home. Male wood roaches are also attracted to lights and find their way inside through various points of entry. Wood roaches just visit, they are not known to infested homes like their cousins do. See photos of wood roaches at: http://bugguide.net/node/view/31624
Are you interested
in reducing urban blight and growing sustainable communities?
Learn how to turn
vacant city lots into productive uses through the development of a variety of
food system techniques at a workshop scheduled for June 5-6, 8:30 AM- 4:00 PM
at the MSU Extension –
Project
participants leave the workshop with improved skills that they can take back
into their communities and pass on to others. This workshop is targeted to urban
gardeners, project planners and food producers. Learn more about Growing Power
at http://www.growingpower.org/.
The cost of the workshop is $25, which includes lunch. Any questions, please call 810-244-8547 or email Terri Novak at novaktl@michigan.gov. (View brochure and sign up
information.) MSU Extension is sponsoring this workshop in partnership with the
Genesee County LandBank
Authority and Urban Community Youth Outreach. Funding is provided by the Applewood Initiative for Gardening & Community,
Community Foundation of Greater Flint; Michigan Food & Farming Systems; and
Jeff
Andresen
Agricultural Meteorology
Geography
High pressure will hold across the Great Lakes region one
more day, bringing a continuation of cooler than normal temperatures Friday,
May 18 across
More widespread showers
and thunderstorms are likely statewide as the front passes through the state
once again. Temperature wise, highs Friday will warm into the 60's to low 70=s
across most of the state. A wide range of daytime temperatures is likely
Saturday, with highs ranging from the 50's north behind the cold front to the
low and mid 70's south in the warmer air. Nighttime temperatures this weekend
are expected to remain in the 30's and 40's across most of the state. Some
scattered frost or freezing temperatures are possible again in interior areas
of the
In the medium range time frame, forecast guidance is
suggesting a relatively flat, west to east upper air pattern during the 6-10
day period with the gradual formation a troughing
feature across eastern