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Vol. 19, No. 2, May 14, 2004 In
this Issue Next issue May 21 |
Choose arborist carefully to treat trees for emerald ash borer |
The onslaught of the emerald ash borer (EAB) in southeastern Michigan has left homeowners searching for methods to save their ash trees and reputable tree care professionals to apply them. "Hiring a tree care company should not be left to chance, or done in a rush," says Robert Bricault, Michigan State University Extension (MSUE) horticulture and natural resources agent in Washtenaw County. "The International Society of Arboriculture (ISA) suggests that, when choosing an arborist, you ask for proof of insurance and references, get all bids in writing as well as dates when work will start and be completed, ask whether cleanup is included, and get signed, detailed contracts. "Ask for hourly rates in the contract in case more work needs to be done," he says. "The ISA also suggests getting multiple bids. Examine low bids carefully to ensure that the company is qualified to do the work." The Michigan Forestry and Park Association suggests looking for arborists with experience, educational backgrounds in arboriculture or landscape horticulture, certification from professional arborists associations, and current pesticide applicator certificates. Companies that belong to professional arborist organizations show a desire to keep knowledge up-to-date, Bricault notes. A lack of understanding about EAB can lead to improper treatments or even needless applications of pesticides, Bricault adds. Currently, only ash trees within the 13-county quarantine zone would potentially benefit from treatments to minimize damage from EAB. Kay Sicheneder, arborist with Owen Tree Service in Attica, says reputable companies demonstrate professionalism in their efforts to educate the public about tree care. "An arborist should be able to explain management techniques available for EAB and research on product efficacy," she says. "They should also explain that treatments are needed annually to protect the ash trees." She also emphasizes that homeowners should avoid companies with high-pressure sales or promises of a cure, and those that claim to be the only company with an answer. "The common theme here is that qualified arborists are well-educated and experienced professionals who need to be able to answer your questions, provide information based on research and help clients make decisions on when damaged trees are beyond the ability of pesticides to be effective," Sicheneder says. Contact your county MSUE office for more information on EAB and ash trees, or go to the Web site http://www.emeraldashborer.info |
Cedar-apple rust
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Cedar-apple rust, caused by the fungus Gymnosporangium juniperi-virginianae, forms galls on juniper and red cedar. For most of the year these galls are greenish-brown and relatively inconspicuous. In the spring during warm, rainy weather like we had this week, orange, gelatinous, tentacle-like projections emerge from these galls. The galls are then readily observed and can be quite disturbing to many people. These slimy galls are now readily visible on cedar. This pathogen alternates between two hosts, apple (or crabapple) and juniper or cedar, to complete its lifecycle. Teliospores produced on the tentacles germinate and give rise to another spore type, basidiospores, which are spread by wind to the alternate host. Once spore production is complete the gelatinous substance will dry and fall from the tree, however the gall will remain for several more years, possibly repeating the cycle in other years. Galls that produced tentacles this spring are likely the result of infections that took place almost two years ago. Juniper are infected in late summer. The following spring gall formation begins, but galls typically don't release spores until the following spring. The symptoms/signs of infection produced on apple are not nearly as dramatic. Both leaves and fruit can be infected, resulting in defoliation and significant crop reduction of susceptible varieties. Managing this disease depends largely on the situation. In situations where there are individual junipers in the landscape it may be feasible to prune out galls. Trees should be checked closely each fall for the presence of newly forming galls. The severity of disease depends on the proximity of the alternate host. In nursery or orchard situations, alternate hosts that are nearby should be removed, if possible, wild plants should not be overlooked. Fungicides can be used to prevent infection of susceptible Juniperus sp. in the nursery. Recommended products include triadimefon, myclobutanil, mancozeb, triflumizole, Zyban, Heritage, or Junction, applications should be made two times at three-week intervals beginning in early August. |
Shade tree anthracnose, again! |
The recent rains, which coincided with leafing out of our oaks and sycamores, have likely set us up for another big year of shade tree anthracnose. In preparing for this article I polled diagnosticians from across the country looking for some new and exciting information about this age-old disease problem, unfortunately I did not come up with much. So, for those of you looking to review.. Anthracnose is a fairly generic disease name, many different plants - vegetables, perennials, annuals, trees, etc. get diseases commonly referred to as anthracnose. When we talk about shade tree anthracnose, we are referring to diseases caused by several different, but closely related, fungi. Oak anthracnose is caused by Apignomonia quercinia (good luck pronouncing that) while A. veneta causes sycamore anthracnose. Both of these pathogens blight foliage, and in some cases, create cankers on twigs, resulting in dieback. Anthracnose foliar lesions are large, irregularly shaped areas of necrotic tissue along the leaf margins and between the veins. Leaf blighting typically begins on lower branches and spreads upward. With a hand lens you should be able to see the fungal fruiting bodies along the veins of infected foliage. Why are we talking about these diseases now? Newly emerged foliage is more susceptible to infection. Last year I spoke to many landscape managers and homeowners that had experienced the damage caused by anthracnose. Many of these people were desperate for foolproof control recommendations. As a rule, fungicides are not recommended for control of shade tree anthracnose. Large, well-established trees that are otherwise healthy can withstand the damage without serious long-term affects. In time, severely infected plants will push forth a new flush of growth from buds that would otherwise have remained dormant. If you are planning to use fungicides to prevent oak or sycamore from anthracnose now is the time these sprays should be applied. Some examples where chemical control might be appropriate include protection of smaller trees or trees not well established, or in "show case" areas where for aesthetic reasons it is important to maintain a disease-free tree. Applications of Protect T/O, Camelot, thiophanate-methyl, or Spectro will help protect foliage from infection. Refer to the fungicide label for application rates and intervals. If you are not inclined to use fungicides to manage this disease, remember that sanitation is also important. Fallen leaves should be raked up and removed, spores of the pathogen remain viable on this dead foliage throughout the winter. In the spring, humidity and rain help spread spores to the newly emerging foliage. Where possible it is helpful to prune and destroy dead twigs and branches from the trees during dormancy (This is probably impossible with large trees.). Some references indicate that white oak is more susceptible to infection than other oak species. Likewise, there are a few anthracnose tolerant cultivars of sycamore available. If you are interested in learning even more about anthracnose, The University of Nebraska has a nice Extension publication that compares anthracnose on several shade trees and includes photos. It can be found on the web at: http://ianrpubs.unl.edu/plantdisease/g1200.htm |
Cleanup hazard trees before the storm |
This week's severe weather throughout Michigan points out the need to evaluate the trees around your property for hazards. While it is impossible to completely prevent tree damage from severe thunderstorms like those that rumbled through this week, it is possible to be pro-active and reduce the likelihood of damage to your home or property. In evaluating the potential of a tree to create a hazard, it is important to consider targets and defects. A target refers to objects or property that a tree or limb would hit if the tree should fail. Common targets are houses, cars, and utility lines. It is especially critical to consider areas where people gather such as pools, picnic tables, and decks. A defect refers to the condition of the tree that may fail and cause damage. Below are some of the conditions that can cause tree hazards. Remember: a complete hazard tree evaluation should be undertaken by a trained professional arborist or urban forestry consultant. The items below indicate the need for a more complete examination. What to look for Decay. Trees or limbs that are decayed may break or fail in a strong wind. Although decay may be difficult to evaluate, there are some telltale signs. One of the most significant is the presence of conks or fungal fruiting bodies on the tree stem. Trees with severe decay may be hollow in the center and give a distinctive sound when rapped with a wooden mallet. Weak branch unions. Branch unions that result in a narrow, v-shaped crotch are common points of tree failure in storms. As the tree grows, bark can accumulate in the crotch and result in a weak point of attachment. This condition is common with many pine species that can develop multiple leaders. In high winds these trees often split into two. Tree species. Because of their wood strength and branch architecture, some species are more prone to failure in winds than others. The possibility for hazard increases with tree age. While no tree is absolutely storm-proof, these are some of the trees that can become hazards at a relatively young age: cottonwood, aspen, jack pine, silver maple, Norway maple. Cankers and cracks. Trees with large cankers or cracks should be checked carefully. These can be weak points in the tree and may also be points that may be decayed as well. Corrective action Move the target. In certain cases moving the target may be sufficient to prevent damage to property and eliminate the hazard. For example if a limb hangs over a portable shed or out-building, moving the shed may be a option to reduce the likelihood of damage. Prune the tree. For hazardous limbs, this is often the best solution. Pruning trees to eliminate dead limbs and weak branch unions is one of the best pro-active steps to reduce possible damage from hazard trees. Remove the tree. If the defect is in the main stem of the tree, removal may be necessary. While this is often a difficult (and expensive) situation, it is better to take a tree out on your own terms than to have it come crashing into your garage or house at 2:00 AM on a stormy night. For more information on evaluating hazard trees, visit the US Forest Service Hazard Tree web page: http://www.na.fs.fed.us/spfo/pubs/howtos/ht_haz/ht_haz.htm |
Phenology report |
Pest-wise on campus it was a slow week, even though the degree days are clipping along at a rapid rate. On campus as of May 13 at noon, temperature accumulations for the Horticulture farm were at 290.4 GDD50 and 392.4 GDD50 for the perennial garden. We are now 15 days ahead of normal for the perennial garden and 6 days ahead for the horticulture farm. Frost injury on red oak and sycamore is visible as curled and slightly browned areas around the margins of the leaves. Cedar apple and cedar quince rust galls are still present on juniper. First mines of elm and birch leafminer are visible now, as small silvery blotches with a tiny brown spot where the leaf was punctured by the female laying an egg. Common lilac at full to late bloom is an indicator for first mines of these sawfly larvae. European pine sawfly larvae and boxwood psyllid nymphs are still busy feeding on their respective hosts. Vanhoutte spirea is at full bloom, an indicator for crawlers of oystershell scale and pine needle scale. Other sites in Michigan Reports from other states; pests
to watch for The Morton Arboretum in Lisle, Illinois reported GDD accumulations of 237 through May 4. Common Lilac, Ohio buckeye, blackhaw and wayfaringtree viburnum and Sargent crabapple were in full bloom; flowering dogwood, horsechestnut, wiegela and Persian lilac (Syringa x persica) were at early bloom. Unlike much of Michigan, Illinois has been experiencing less than average rainfall. Leafroller larva were found on dotted hawthorn, and Judd viburnum damaged by viburnum borers feeding in the cambium were found. The larvae overwinter under the bark. The adult is a clear-winged moth (Synanthedon sp.) that emerges in June and lays eggs on the stem near the base of the plant, often close to wounds. University of Illinois plant clinic in Carbondale, IL reported a lot of calls about diseased Vinca minor. However, the article didn't state whether the cause was Vinca stem blight (Phoma blight) or Rhizoctonia sp. They too, are reporting gypsy moth hatch and expecting oystershell scale crawlers soon. It seems to have been a fairly slow week for pests and diseases in both Illinois and Ohio, too.
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Cornell guides for ornamental pests available |
The 2004 Pest Management Guide for Commercial
Production and Maintenance of Trees and Shrubs from Cornell
Cooperative Extension and the companion volume, 2004 Pest Management
Guide for Commercial Production and Maintenance of Herbaceous Perennials
are now available through the MSU Extension Bulletin Office, 117
Central Services, Michigan State University, East Lansing, MI 48824-1001.
Phone: 517-353-6740, Fax: 517-353-7168 Office Hours: M-F 8:00 AM
- 5:00 PM. The bulletins may be ordered online at: The guides contain current pesticide recommendations. E-2782, the tree and shrub pest management guide, retails for $26.00; the herbaceous perennial pest management guide, E-2783 retails for $28.00. Both guides contain recommendations for management of insects and mites, diseases and weeds. |
Conditions perfect for needle cast diseases of Christmas trees |
This is a good time to point out the fungal pathogens that cause Rhabdocline and Swiss needle cast of Douglas fir and Rhizosphaera needle cast of spruce will begin their yearlong infection of the 2004 needles unless you begin your spray programs. For these diseases to initiate infection, two events must occur-and they are occurring right now. First, bud break and shoot elongation must be occurring and the needles should be half their ultimate size. Second, the spores of the fungus must be released from last year's infected needles. These spores will ride to the new needles on rain-soaked pathways where the pathogens will begin their infection process. So bud break, spore release and rain lead to needle cast infections in Douglas fir and blue spruce, and that is happening right now in most of the Christmas tree plantations growing Douglas fir and spruce. Since the materials that work on Rhabdocline are effective on the Swiss needle cast pathogen, you will get control of two diseases for the price of one. Always follow label instructions when spraying. The most effective material for control of Swiss and Rhabdocline is chlorothalonil. All studies show that the seed source Shuswap is resistant to Rhabdocline and these trees do not need to be sprayed for Rhabdocline saving you money and the environment fewer molecules of chlorothalonil. See the April 30, 2004 Landscape Alert for more information. |
Spruce needle drop |
Many growers have heard
of SNEED, spruce needle drop, and many trees appear to have symptoms
similar to those described by plant pathologists in other states.
These symptoms usually appear on second-year needles and include
needles turning chlorotic, gradually turning purple-brown. Most
branches will drop their needles, leaving the branches with sparse
foliage, just behind the current year's flush of growth. If you
take out a hand lens, you will usually see small black dots on the
stems, and the base of any attached needles may look as if they
are dead, even if the needles are still green. These small black
dots are fruiting bodies of the fungus, Setomelanomma holmii that was isolated
a couple years ago by Wisconsin forest pathologist Glenn Stanoz.
The USDA determined the name of the fungus. The USDA calls this
fungus the cause of SNEED, but there is no research, at this point
that shows this is the case. Yes, this fungus can
be found on trees with SNEED symptoms, but it can be found on trees
without symptoms, too-at least in Michigan. The fungus can be found
throughout the spruce tree but only portions of the tree may show
symptoms. Much more research must be conducted before the cause
and management of this problem is known. In the meantime, other
causes of spruce problems, including cytospora canker and Rhizspearea
needle cast need to be ruled out in the majority of cases. As we
find out more, we will let you know. Here is a recent web site article
from Missouri on the problem: http://www.na.fs.fed.us/spfo/pubs/newsletters/csfhw/nov03/sneeddetail.pdf If you think you have SNEED in your plantation, please email Dennis Fulbright at fulbrig1@msu.edu or call 517-353-4506. |
Christmas tree and forestry insect update |
Pine shoot beetle Pine needle scale Eastern and Cooley spruce galls Spruce spider mite If you have mites, the best product to use is Savey. This product will kill the eggs and immatures for the rest of the season, but it will not kill the beneficial, predatory mites. Using Savey is like having your cake and eating it too. Savey will provide good control, plus the predatory mites will continue to hunt down the nasty spider mites for the rest of the season. Gypsy moth Tiger beetles - not emerald ash
borer Spruce needleminer |
Emerald ash borer look-alikes |
It's that time of the year when people bring in beetles and other insects that resemble, at least somewhat, the emerald ash borer (EAB). Last year, the most commonly submitted EAB suspect was the sixspotted tiger beetle, Cicindela sexguttata (Coleoptera: Carabidae formerly Cicindelidae). This attractive, brilliant, metallic-green beetle is about 0.75 of an inch long with white spots on its back. It has very long legs and is a very fast runner and very difficult to catch. It is found throughout Michigan and is one of our most commonly encountered tiger beetles. It appears early in spring after having spent the winter in the same burrow it hunted from as a larva. Like all our adult tiger beetles, the six-spotted tiger beetle is a voracious hunter. It hangs out on a sunny vantage point looking for potential prey and for potential predators (and would be captors). This species has a two-year lifecycle. This year several people have also brought in a different species of beetle, which to them looks like the emerald ash borer. I was kind of surprised to find the grape flea beetle, Altica chalybea (Coleoptera: Chrysomelidae) in their various plastic bags and small containers. I have been watching these beetles on a patch of wild grape I have in my yard since the buds began to swell over a month ago. Their springtime behavior is decidedly and openly pornographic. This beetle is metallic blue to greenish in color, which I guess gives it an EAB-ish look, but it differs from EAB in that its body is oval shaped and measures only about a 0.25-inch in length. And, they hop when approached. The grape flea beetle is a native insect that occurs throughout the Central and Eastern US. The beetle feeds on the buds of wild and cultivated grapevines and Virginia creeper. The larvae feed on the leaves. Grape flea beetles overwinter as adults that attack the swelling grape buds by boring into them and hollowing out the inside. The larvae and summer adults feed on the tender leaf tissues but avoid the leaf veins. Newly hatched larvae are dark brown, but as they grow, their color lightens. By the time the larvae reach maturity, they are light brown and about 3/8 of an inch in length. The larval body is covered with black circular and rectangular plates of various sizes, which give it a spotted appearance. These plates become more prominent as the larva matures and its body becomes lighter in color. There is only one generation per year. |
Paper wasp nest building is underway |
Last summer, around the middle of August, a wasp stung my eight-year-old daughter as she slid down her slide in the backyard. The slide is part of a gym set that includes swings, monkey bars and other potentially dangerous playthings that young developing primates enjoy playing on. As she screamed, I went for my trusty can of wasp killer. To my surprise, I found no less than 15 European paper wasp nests on the underside of her slide. I found others located in and on other parts of the gym set. Any and every opening that offered some protection from rain seemed to be occupied by a paper wasp nest. They ranged in size from 30 to 50 cells. They had been there all summer without bothering my daughter as she played on her gym set pretty much on a daily basis. Something had changed, now they were very aggressive. I quickly sprayed each nest and will readily admit to enjoying watching the occupants writhing in the foam. I expanded my search to other parts of the yard and outbuildings. It became increasingly clear that I was going to need several more cans of wasp spray. I must have destroyed over a hundred nests that day. I found them almost everywhere I looked on the buildings. The European paper wasp, Polistes dominulus (Hymenoptera: Vespidae) has taken over the Number 1 spot on the list of Most Annoying Vespids in Michigan and probably throughout the Eastern US. A spot formerly held by the German yellowjacket. The telephone calls about paper wasps began this spring as soon as the weather warmed and the overwintering queens were out looking for potential nesting sites. Many told the same kind of story I told at the beginning of this article. They had nests everywhere last summer. They want to know what can be done to prevent this from happening again this year. Most ask if there is some kind of repellent that can be sprayed around the yard and under decks to keep these wasps away. I am sorry to report that no, there is no such wasp repellent. While commercially available wasp traps will capture yellowjackets, they don't interest paper wasps in the least. The only reliable method that I know of to control paper wasps is locate and spray the nests, preferably in the early morning when the queen is sitting on the nest. The paper wasp nests that I have seen around my house now are at the 6- to 8-cell stage with a single queen tending the nest. Now is the perfect time to give them a squirt of wasp killer. Please be considerate of your mail delivery person and check inside and under your mailbox as these are among the wasp's favorite nesting sites. Lock and load! European paper wasp is an Old World species that has a native range from Europe to China. The species is by far the most common Polistes in Western Europe. It has successfully invaded the Western Hemisphere, both in South America and North America. It was first discovered in the US in Cambridge, Massachusetts in 1981. Since then it has spread throughout the US. It was first found in Michigan in 1994. The European paper wasp has quickly replaced our native brown and tan paper wasp, P. fuscatus, as the dominant Polistes species. You can identify a paper wasp by its longer body, thin wasp-like waist, and the open-celled paper nest. The nests hang downwards and are common under eaves and inside outbuildings that offer access through cracks and open windows and doors. No mud is found in paper-wasp nests. The hornets and yellowjackets have thicker bodies and build paper envelopes around the nest combs in which the young are raised. These nests can be much larger than the paper wasp nest and are often football shaped. The European paper wasp is black with bright yellow markings like a yellowjacket. It is much more likely to nest in cavities and on a vertical surface as long as some type of overhang provides some protection. The European paper wasp seems to attack people with much less provocation than our native paper wasp, especially during late summer. |
Early spring temperatures inside a Michigan polyhouse: An update |
One of the special features of Michigan Automated
Weather Network (MAWN) automated weather station at Northland Farms,
Inc. near West Olive is an extra set of temperatures taken from
inside an adjacent polyhouse covered by material with a 55 percent
shading factor. Indoor temperatures were monitored in the air at
a two-foot level and in planting medium in a one-gallon plastic
container at a one-inch depth. As is the case for all air temperatures
monitored in the MAWN network, temperatures were sampled by the
dataloggers every 60 seconds with data output recorded as absolute
maxima and minima every 24 hours, and as averages once every hour.
Observed weather data from this station are available via in Internet
at: A comparison of GDD50 accumulations at the end of the "spring" season when the polyhouse material was removed (January 1- May 11) is given in Figure 1. The GDDs were calculated with the Baskerville-Emin methodology using daily maximum and minimum temperatures at the two locations inside the polyhouse as well as the outdoor adjacent air temperatures. Significant GDD accumulation for the indoor air temperature began in late February, followed by the indoor container in mid-March and the outdoor air temperature in late March. Totals as of May 11 indicate a difference of about 374 units (In mid-April, the difference was approximately 300 units.) between the indoor and outdoor air temperatures and 174 units between the indoor air and container temperatures (In the earlier April comparison the difference was about 200 units.). Using early season climatological normals for west central Lower Michigan, the indoor versus outdoor difference translates roughly into a lag of 30-40 calendar days (i.e. phenologically, one would expect to reach a given growth state 30-40 days earlier inside the polyhouse versus outside). The 374 additional GDDs in the early season are also significant from a climatological perspective, representing from 10 to 15 percent of the entire (outdoor) growing season GDD50 total accumulation for this area of west central Michigan. |
Weather news |
It has been one week now since a frontal boundary draped across the Great Lakes Region has meandered back and forth across the state, resulting in widespread showers and thunderstorms on almost a daily basis. Rainfall totals for the seven-day period between May 7-13 ranged from less than 0.25 inches in the Upper Peninsula to more than 5 inches in sections of the central and southern Lower Peninsula, where localized flooding was reported (Note that normal rainfall for the entire month of May is on the order of 2.8 to 3.2 inches.). While it led to major delays in spring fieldwork, the rain also significantly reduced or eliminated long-term precipitation deficits in many areas. On Friday morning (May 14), the frontal boundary was located across Michigan from near Sault St. Marie to just west of Chicago. It is expected to move eastward and out of the state by early Saturday morning. In the short term, showers and thunderstorms will be a good bet once again, especially in eastern sections of the state. Rainfall coverage Friday is expected to range from less than 50 percent in western sections of Upper Michigan to near 100 percent in eastern sections of Lower Michigan with 0.50- to 1.00-inch totals possible in most areas. Drier weather is expected to develop statewide by Saturday and continue through Sunday. Low temperatures will decrease to the 30's to low 40's by Saturday. Widespread freezing temperatures are expected overnight Friday into Saturday morning across western and central sections of the Upper Peninsula, while scattered frost will be a possibility in eastern areas of the Upper Peninsula and interior areas of northern Lower Michigan. Frost is also a possibility in northeastern sections of the state Sunday morning. In terms of precipitation, the next weather system to impact the state will bring a chance for showers to western sections of Upper Michigan by late Sunday or early Monday, and statewide Monday. The expected break in the very active weather pattern this weekend over the region could be relatively brief. Current medium-range forecast guidance suggests upper air troughing across the western US with broad ridging across the east and an active storm track through the Midwest. For both the 6-10 day and 8-14 day time frames, covering May 19-23 and 21-27, the NOAA CPC outlooks call for above normal temperatures for most of the state except central and western sections of the Upper Peninsula, where normal temperatures are expected. As has been the case recently, precipitation totals are expected to remain above normal both state- and region-wide. |