David L. Roberts,
Site: Emerald Ash Borer Homepage
|An ash in the middle stages of decline, showing stunted sparse foliage on the branches and abundant shoot proliferation from trunk. It is questionable that this tree can be saved in this stage. Upon a returned visit in June, 2002 revealed a completely dead tree. (Fig. 35)|
~~~~~2002~~~~~~~~~~~~~~~~~~~~~~~ "EAB" Management Procedures & Ash Tree Sanitation, 2003 How Well Do Insecticides Work for Emerald Ash Borer Handout Some Perspectives on Long Term Management Identification of Stages of EAB Decline & Whether Treatment is Warranted Photo Gallery I - Emerald Ash Borer Photo Gallery II - Emerald Ash Borer Ash Decline in Michigan June Report Ash Yellow Diagnosis Survey Sponsorship Acknowledgments ~~~~~2001~~~~~~~~~~~~~~~~~~~~~~~ Ash Decline in Michigan Introduction to the Problem Ash Decline Report .pdf Ash Yellows, Ash Decline, or What? Ash Yellows Decline: Part II Ash Trees, Field Update Identify & Manage Ash Yellows....NE Area Forestry Publication Winter Pruning Site Directory Free download for .pdf files
ASH TREE PROBLEMS
David L. Roberts, Ph.D.
Michigan State University
Close up of a metallic, flat headed wood boring beetle associated with declining ash trees. (Fig. 36)
Ash Decline in Michigan - JUNE, 2002 Report
As recorded since last summer, Ash trees are dying by the thousands in Southeast Michigan. Last summer, I began a series of investigations to determine the cause of the malady, which I described as “Ash Decline”. In some areas, this malady is affecting virtually 100% of the trees. This report will bring us up-to-date on this unfolding problem.
Results of the Ash Yellows Survey: One survey conducted this spring involved submission of ash samples for the detection of Ash Yellows. Ash Yellows is a disease caused by a phytoplasma, an organism with some similarities to a bacterium. About 65 samples were collected representing in excess of $6,000 of diagnostic tests. Out of approximately 65 trees sampled for the detection of ash yellows only three trees tested positive for Phytoplasmas utilizing a special PCR (DNA) test. The results of this survey tend to provide evidence that Ash Yellows is not a major factor in the overall Ash Decline problem we are experiencing in SE Michigan. Nevertheless, this work has been extremely important for delineating the causal factors in the Ash Decline problem. I would like to thank officials in Canton, Livonia and the Michigan Arborists Association for funding this research.
A Metallic Flat Headed Wood Borer "Emerald Ash Borer" Associated with Ash Decline:Last fall I published on my web site the suspicion of the involvement of borers in Ash Decline. This suspicion was based on the observations that many ash which were declining appeared to be a consistent association of borer activity with the declining trees. Last summer, larvae were collected and submitted to my entomology colleagues at MSU. To the best of their abilities the larvae were identified as a species of Agrilus, probably the two-lined chestnut borer. Since late May of this year, adults of this larval stage have been emerging. Thanks to my contacts around the SE region, we’ve been able to collect these insects from various geographical areas. The insect began emerging in late May, through D-shaped holes, measuring approximately 1/8 inch wide. Even though the insect appears to be an Agrilus sp, related to the two-lined chestnut borer and bronze birch borer, it is apparently not the two-lined chestnut borer as originally believed. The species of this insect is currently being identified by my MSU entomological colleagues.
Woody Woodpecker and Distribution of Ash Decline: One interesting phenomenon I began observing last winter was the intense woodpecker injury on trees infested with the borer. On trees with the Ash Decline/Borer problem, small patches of bark have been stripped away and single holes have been made in the bark for apparent extraction of the insect by woodpeckers. The removal of bark areas by birds can be easily observed from a distance as the areas with removed bark appear lighter in color than surrounding bark. In observations, the amount of woodpecker activity seems highly correlated with the amount of decline in the tree as evidenced by the canopy cover, canopy density and number of dead branches. According to the literature, wood boring beetles are a favored food of the downy and hairy woodpeckers. I have now detected this ash decline problem as far south as Romulus, as far west as the Ypsilanti/Ann Arbor area and as far north as Rochester Hills, representing approximately 300 square miles of ash decline. Every city or township delineated by this area should be affected, but I have personally found this Ash Decline/Borer/Woodpecker situation in Romulus, Dearborn, Ann Arbor/Ypsilanti, Novi, Northville, Canton, Livonia, Westland, Farmington Hills, Beverly Hills, Birmingham, Bloomfield Hills and Rochester Hills. This is not a complete list; other cities, townships and counties are most likely affected, and we will keep you apprised of our continued discoveries on this important problem.
How to Identify the Ash Decline Problem in Southeast Michigan: In order to determine whether specific trees are affected by this malady, some of the following symptoms characterize the Ash Decline. All size and ages of trees may be affected except small seedlings of less than 1-2 inch trunk diameter:
If anyone finds evidence of the above described symptoms of ash decline outside the above discussed areas, I would appreciate it if you would report the location (address) to me at my email address and thank you.
- Initial thinning and/or yellowing of the foliage. Affected foliage may be over the entire canopy or limited to certain branches.
- Epicormic Shoots: A proliferation of succulent shoots (suckers) may develop from the trunk, the trunk-root collar area or the scaffold branches. These shoots may grow more than four feet in one season and have abnormally large leaves. Epicormic shoots are not always present on declining trees.
- Wood Pecker Injury: Another identifying characteristic which has come to light over winter is intense activity of woodpeckers on trees as they apparently search for their favorite food-wood boring beetles. Usually, large trees are preferred by the woodpeckers.
- Tunneling Beneath the Bark: Even though the bark may appear tight on many trees, there is in fact extensive tunneling under the bark of affected trees. Look for tunneling by peeling the bark down to the cambial tissues. Tunneling by insects will be about one-quarter inch diameter. On some trees, tunneling may occur without much evidence of the D-shaped emergence holes described below.
- D-shaped Emergence Holes: Trees which are affected by the ash decline problem in SE Michigan will exhibit D-shaped emergence holes on the trunk or branches, which are typically greater than 1-2 inches in diameter. Obviously, the more severely affected the tree, the greater the number of emergence holes.
- Dieback/Death: Most trees which exhibit the ash decline/borer complex will eventually exhibit branch dieback or complete death. In reality, the problem may have been present but unnoticed on particular trees for quite a while. However, trees appear to have declined/died very quickly, in some cases as little as one year.
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"Emerald Ash Borer Management Procedures" March, 2003
THE FIRST STEP
For any Ash owner, THE FIRST STEP to consider with controlling the Emerald Ash Borer (EAB) is to determine whether the ash trees are to be SAVED or whether the ash trees will be DESTROYED by the EAB or by the owner. This step must be determined quickly because ash which are in the path of the borer may decline from healthy to beyond salvage in as little as 2 months. Also, there are legal and ethical considerations in managing the EAB on ash; these will be addressed.
SAVING ASH TREES:
Saving ash will involve a variety of inputs and will necessitate implementation year after year. Because the EAB is an exotic, introduced pest with little natural impediments to its activity, insecticide applications will be necessary every year for the foreseeable future. Simply keeping your trees in good health is not sufficient to ward off EAB attacks. Insecticide treatments will be a long term investment which may still not save your trees. We have little information on the efficacy of treatments, but research is prioritizing this need. Various groups are busy performing pesticide trials so we will keep this web site posted with new information.
Perspectives on Long Term Management
Saving Ash Trees: The Stages of EAB Decline
Initially we believed that trees which exhibited up to 40-50% decline would respond to our insecticide treatments. We were wrong. Research has shown that preventative treatments (treatments before infestation by the EAB) or curative treatments on ash trees already infested but showing no more than 10-20% dieback may (or may not) respond. Also, please review my Diagnosis/Detection of the EAB and remember, early detection is the key to saving your ash.
Saving Ash Trees: Cultural Inputs
Insecticide treatments alone will not protect ash trees from successful attack by the EAB. Trees must be in good health to help ward off attacks. Keep trees in good vigor and health with adequate nutritional applications if needed. Fertilization every year or so may help to improve vigor in trees, particularly those that exist in poor soils. Ashes have often been planted in poor sites because of their hardiness in tolerating adverse conditions. WATER is an important nutrient for ash trees and the EAB tends to be drawn toward trees under stress, especially drought stress. Keep trees watered during dry periods. A good rule, depending on soil conditions, would be one deep root watering per week during dry periods. Avoid excesses of water, fertilizer AND mulch, which may stress trees.
Saving Ash Trees: Sanitation
Sanitation refers to cleaning or eliminating unwanted material. In the case of ash trees, trees which are not to receive SAVING inputs but which are infested or in the immediate path of infestation should be eliminated because these trees can act as “brood trees”. Brood trees help to build up populations of the EAB so that their attacks on healthy, desirable trees are more successful. Eliminating the EAB food source and their habitat will reduce populations to more manageable levels so that our other inputs will be more successful. In some uncommon sanitation cases, eliminating highly infested branches may save the rest of the tree if the EAB is not uniformly distributed through the tree.
Saving Ash Trees: Insecticide Treatments
Unfortunately, insecticide treatments will be a necessary requirement for saving ash trees. The insecticides and delivery methods listed below are options for consideration, respectful of the fact that we do not have conclusive evidence that any will be effective in saving a particular ash. There will be differences in levels of desired inputs-some may desire to implement all three delivery techniques whereas others will chose only one. Until we know more about efficacy of insecticide treatments, two or three delivery methods will probably be better than one. The choice is yours.
Note: Homeowners would be best advised to have commercial applicators treat their ash trees, particularly if they have large trees. Small trees (6 inch trunk diameter or less) can be treated very effectively by homeowners. Be sure to read the label, follow the directions and wear the necessary personal protective gear.
Click link : How Well Do Insecticides Work for Emerald Ash Borer
David Smitley, Ph.D. & Deborah McCullough, Ph.D. - Department of Entomology, Michigan State University
Destroying Ash Trees
EAB infested ash trees which are beyond salvage or which will not be maintained through the Ash SAVING techniques should be destroyed. Destroying ash under these circumstances is not necessarily a legal responsibility (although communities may adopt resolutions or ordinances prescribing ash management) but a moral or ethical responsibility. Ash trees in EAB infested areas which are not maintained can serve as brood trees where EAB populations may build up and continue to put additional INSECT PRESSURE on healthy trees or trees which are under Maintenance SAVING techniques.
Destroying Ash Trees: The Methods
Chipping, burying or burning are the most preferred methods for minimizing EAB activity and survival. Ash wood cannot be taken out of quarantined counties except for provisions mandated by the Michigan Department of Agriculture quarantine Act (www.michigan.gov/mda). And, it would not be prudent to take ash wood to areas of quarantined counties where the EAB doesn’t already exist. Ash can be used for firewood but there are certain guidelines which will help to minimize EAB influences (below).
Destroying Ash Trees: Timing
It is desirable to destroy ash trees soon after it is decided not to save them. However, because adults EAB begin emerging in May, it is definitely desirable to destroy infested trees before May 1st every year to minimize adult emergence, which if they successfully emerge, are capable of attacking many more trees in an area.
Destroying Ash: Firewood
Ash wood from trees can be used for firewood, but firewood cannot be taken outside of the EAB quarantined areas according to MDA Quarantine Act/Mandate. In firewood, EAB adults will emerge from ash the spring after the wood was cut during the previous winter. Hence, ethically, ash firewood should be covered and “sealed” with a tarp from May through August, to prevent escape of emerging adults. Ideally, ash firewood should be used as soon as possible after cutting, ex. the same Winter Season it is cut. Ash firewood which has been sitting for more than a year is of no concern for the EAB because larvae can only develop in live trees and any adults would already have emerged within the first year after tree cutting.
Destroying Ash Trees: Replant Recommendations
One of the main questions to consider if ash are to be replaced is the type of tree recommended for planting. There is not ONE tree that fills every need so it would be wise to consider many possibilities. The possibilities are listed on the Alternatives for Ash Tree ( .pdf link). Whatever the case, to avoid major epidemic catastrophes such as the EAB and Dutch Elm Disease, ALWAYS use diversity in plantings.
Above article is also available as a printable document (saved in pdf format)
Click to get:New Exotic Pest, Emerald Ash Borer & Revised Control Techniques.pdf
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Some Perspectives on Long-Term Management
In recent visits to some sites affected with the emerald ash borer, it has become apparent that there is extensive confusion about control practices and costs, especially from a long-term standpoint. One particular condo complex received an estimate of $9,000 to "save" their 67 ash trees; this estimate included insecticide treatment, fertilization and pruning, which are all reasonable practices to help recovery or which might help prevent further decline of ash trees from emerald ash borer infestations. For many, such estimates would be considered exorbitant, given that intense management practices had not been previously designated in their landscape budgets. I was asked by the condo association board members whether these were reasonable control procedures and whether their trees would be "cured" of emerald ash borer.
We really don't know how efficacious our currently recommended treatments will be until we’ve completed some field trials, which are underway. These treatments are reviewed herein, and in the current and previous issues of the Landscape Alert. But what readily became apparent with the above condo situation and with many other landscapes is the misconception that treatments would need to be applied only one year and that the emerald ash borer would not need to be managed in subsequent years because treated trees would be "cured" forever of the dreaded insect. Regrettably, because of the apparent aggressiveness of this insect at this time, it is likely that attacks and further decline of ash trees will continue after insecticide treatments are discontinued. Obviously, many citizens are not budgeting for long-term health care of their ash trees. The long-term costs of maintaining ash trees along with possible mixed treatment results might not prove satisfactory for many people who have ash trees in the emerald ash borer infestation areas.
In the above condo situation, I suggested several possible approaches. The most reasonable approach, since they had not budgeted or would not likely want to budget for such costly long-term treatments, was to treat some of the highly visible and desirable trees in apparently good health, remove some of the medium to highly infested trees, followed by planting of diverse species of trees for replacement efforts. This condo complex had an advantage of having a diversity of many large trees; the removal of some ash trees would not pose a significant shock to their landscape. I think their long-term approach may be to replace most of their ash in the next few years.
Other landscapes with high percentages of ash trees may adopt a different approach, perhaps electing to treat many of the trees while budgeting for and implementing a gradual replacement program. Still, others with highly desirable ash trees or trees of great significance to their owners, or for a variety of other reasons, may opt for very long-term management procedures.
Above article is also available as a printable document (saved in pdf format)
Click to get:New Exotic Pest, Emerald Ash Borer & Revised Control Techniques.pdf
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Ash Decline in Michigan - 2002
An astonishing number of ash trees (Fraxinus sp.) (white ash, green ash) are currently dead or in various stages of decline around Michigan. An area, which has a very high percentage of ash trees affected by this malady, is delineated by Livonia, Plymouth, Canton and Dearborn in Southeast Michigan. It is estimated that 10,000's of trees are affected in this area alone. In small areas, such as several square blocks or a square mile area, in excess of 90% of the ash trees may be affected The economic impact is staggering when removal, disposal and replacement costs are considered. Since we’ve began investigating this area, other reports from elsewhere in Michigan confirm an ever increasing problem both in natural areas, in landscapes, and in some nurseries. Until we have determined the cause(s) of the problem more succinctly, I have elected to call the problem “ash decline”.
Symptoms: The earliest symptoms of ash decline is a yellowing of the foliage on one branch or section of the tree. Over the period of a growing season or several years, the chlorosis extends into other areas of the tree, with eventual dieback, stunted growth and sparse foliage. Trees usually eventually die. An apparent common recovery mechanism on many of these trees is the abundant and dense proliferation of “adventitious” shoots from the main trunk or lower scaffold branches (see Fig.1). This proliferation of shoots undoubtedly indicates a very healthy root system, probably precluding the possibility of a severe root rot disease as the primary incitant.
Cause of Ash Decline in Michigan: At this time, we are uncertain of the exact cause of the ash decline. However, two insects, the red headed ash borer and two-lined chestnut borer (Fig.2a and 40), have been identified in association with ash decline. These two insects are considered secondary pests, attacking trees under stress. It would not surprise me that other borers or insects or diseases are eventually associated with ash decline. Stress factors which may attract borer problems include: drought, winter injury, adverse soil conditions (compaction, poor drainage, root suffocation from too much irrigation, etc.), girdling from roots or nylon rope/baskets, and other diseases such as ash yellows. Entomologists often suggest that secondary borer insects are simply performing their natural role by attacking trees under stress. While this is probably true, there is an undeniable fact that no ash tree proceeds through its life with out some sort of stress. The high populations of stressed ash trees (some would argue over-planting of ash) exacerbated by the unusually high population of borers in some areas probably represents an ever increasing insect pressure on semi-healthy or healthy trees. This epicenter effect has been noted in the Canton, Plymouth, Livonia and Dearborn areas.
Management of Ash Decline: At this time, there are probably several management procedures that can be employed to inhibit ash decline and prevent further spread of the problem.Sanitation:
All ash trees which are dead or in advanced decline should be removed and properly destroyed. Based on current understanding, I think that any tree which exhibits 50% or greater branch loss should be removed. Perhaps we will revise this to 30 or 40% in the coming months as more information is gathered. Proper disposal includes chipping, burning, and burying. If wood is to be kept for firewood, it should be burned in the coming winter. If the firewood is to be dried for a year or so, it should either be debarked or sealed under a tarp during the warm season. These methods should help minimize spread of the insect borers. (Also, review my Winter Management through Sanitation.)
In some areas where ash decline is a problem, it is possible that ash populations are too high, facilitating the epidemic. Consider alternative species of trees if at all practical.Reduction of Plant Stress:
Key to reducing susceptibility trees to borer activity is to reduce stress and increase vigor in trees through supplemental water and fertilization; excesses of water and fertilization can also stress trees. Proper planting and site preparation can also help reduce problems later in the trees’ life. Various cultural practices aimed at increasing tree health are vital to reducing the chances of ash decline.Insecticide Injections:If advice and assistance is desired, consult your local arborist and landscaper. They can offer assistance in maintaining established trees and for finding alternative plants.
Although not demonstrated, insecticide injections should help minimize borer activity in trees and possibly help trees through stressful periods. These injections may also help reduce the threat from high borer populations in certain areas. Various injection methods are available; consult your local arborist for details.
There are several areas which need attention before we can truly finalize our understanding of ash decline in Michigan. First, we need to determine species of ash most susceptible; there may be species or varieties of ash that are less susceptible to ash decline. In the spring of 2002, a diagnostic survey should be performed on a representative sample of ash trees to determine if ash yellows or other causes are involved in ash decline. Additionally, field control studies can be implemented to try to inhibit further ash decline development in our communities.
Above article is also available as a printable document (saved in pdf format)
Click to get: Ash Decline in Michigan .pdf
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Ash Yellows Survey - June, 2002
Tens of thousands of Ash trees are declining around the state. The problem is particularly acute in the southeast region, especially in Wayne County. I have labeled the problem “Ash Decline”, perhaps a catchall, until we find a more definitive answer to the cause of the problem.
Narrow Window of Opportunity for Ash Yellows Diagnosis:
One of the prominent hypotheses for the decline of these ash trees is ash yellows, caused by an microorganism known as phytoplasma. This microorganism, somewhat related to bacteria, cannot be cultured by traditional laboratory methods and hence, is difficult to detect. Perhaps the best method of diagnosis of ash yellows is by PCR, a DNA based detection technique. Unfortunately, there is a very narrow window for detection of the phytoplasma. The earliest emerged ash leaves in the spring contain the organism is greatest populations for detection; later foliage offers declining phytoplasma numbers and reduced chances of detection.
Michigan Arborists Association lead by Mike Barger of Mike's Tree Surgeon, Inc. and its members have provided a generous donation to cover the costs of some of the analysis fees, as well as, the city officials from Livonia and Canton who additionally funded samples from within their respective communities. Thank you all for supporting our Southeast community PCR surveys.
Photo courtesy of
Daniel Davis of MSU
captures Dave Roberts
during his presentation
with a group. (Fig. 37)
I would like to thank the following individuals and groups for participating in research leading to the discovery of the emerald ash borer: Mike Myers, Shadetree Mechanic, Mark Baldwin, Mark Baldwin & Associates, Guerin Wilkinson, Greenstreet Tree Care, Mike Barger, Mike’s Tree Surgeons, Bill “Doc” Pickardt, American Tree, Steve Printz, City of Novi, Mike Jasso, Jr., Jasso Tree, Chris Pargoff, City of Livonia, Canton Township, Carl Dolhoff, Global Re-Leaf, (retired MDA Inspector), Jerry Kuchera, Bloomfield Township, Kristine Hahn, MSU Extension Wayne Co., Karen Reynolds, MSU Extension Washtenaw Co., Bob Bricault, MSU Extension Washtenaw Co., Master Gardeners of Wayne, Oakland and Washtenaw Co., Dr. Deb McCullough, MSU Entomologist, Dr. Dave Smitley, MSU Entomologist, Tom Ellis, MSU Entomologist, Gary Parsons, MSU Entomologist, Michigan Arborist Association, and all local residents who provided assistance or participated in collecting samples. Thank you all, Dave.
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ASH Yellows, ASH Decline, or What?
Working to find a solution to your ash tree problems in Michigan
Last fall of 2001, I received a large number of calls concerning ash problems this season. From your descriptions and from my observations, many of the trees exhibit symptoms including slow leafing out, no leafing out (especially on some branches), dead branches, and dead trees (rarely). Often, the cambium is still green but many buds are necrotic. In some of the examples, the trees were fine last year but are compromised this year. Many of you apparently have decided that this problem is "ash decline"...and you could be correct in many of the cases. Let me review some of the problems we can expect to see on ash. It may take some very involved investigative work to determine the actual problem on a particular ash. (Ash family)
We are currently witnessing abundant anthracnose in some areas. This fungal disease appears as reddish-brown blotches that distort the leaf when they expand and coalesce. This should not be confused with leafminer. Control for anthracnose is probably too late this season, but the disease is rarely life threatening to the tree. Trees affected rather severely with anthracnose and that have not received any supplemental nutrients for several years, however, may benefit from a moderate fertilization.
Ash yellows is caused by a phytoplasma (formerly called mycoplasma-like-organism). Although phytoplasmas are remotely related to bacteria they produce symptoms similar to viruses. Some of these symptoms include lighter green and smaller foliage, reduced growth (stunting, shortened internodes), tufted foliage, rosetting of the foliage (loss of apical dominance), twig or branch dieback, witches brooming (or epicormic foliage) on the branches and main trunk or stump, vertical cracks on the lower trunk, freeze injury on the trunk. All symptoms may not be present. There also may be very mild symptoms or practically no symptoms in some trees. The disease tends to be less severe and slower in progression in green ash than in white ash.
Leafhoppers are probably the primary vectors of ash yellows, but spittlebugs may also be involved; do not try to control these vectors because such efforts are expensive, potentially toxic to the environment and virtually worthless. Some neighboring states have completed surveys and have determined that a significant portion of the natural ash populations in certain localities are infected with the ash yellows organism. I suspect Michigan would test similarly.
The term "decline" is normally ascribed to situations in which we are uncertain of the primary causal factors. A number of factors have been associated with ash decline, a.k.a "ash dieback." These factors include ash yellows, winter injury, several canker fungi, drought and several viruses. Some believe that ash decline is primarily ash yellows with other contributing factors-drought, winter injury, fungi, etc. Symptoms of "ash decline" mimic those of ash yellows. As with ash yellows, death of the tree may occur in one to several to many years.
Verticillium wilt may cause typical dieback symptoms in ash similar to those symptoms we witness in other plants. One of the confusing factors about verticillium is that in some species of ash, the classical vascular discoloration caused by the fungus may be faint or not even visible. Hence, laboratory testing is required to demonstrate presence of the fungus.
We don’t always understand why different plants are affected differently in different winter conditions. The growth in ash species depends to a great extent upon adequate spring moisture. It’s possible that several years of drought may negatively impact trees and subsequent winter injury may ensue. Add a dash of road salt and these factors may complicate the diagnosis.
Remember that poor soil conditions, improper planting, improper care, chronic excessive mulch, girdling roots etc. may cause some of the same symptoms described for other diseases.
Obviously, the first step in managing problems on ash trees is accurate diagnosis. As might be expected for the above problems, which are more lethal or serious, there are not many very good control efforts. Sanitation (removal) is important so that other nearby trees, if still healthy, will be less likely to be infected. (Back to top)
Images Loading:Ash Yellows Decline: Part II September, 2001
As reported in a couple of (Crop Advisory Team) CAT issues ago, I related some of your concerns about dying and declining ash trees. I recently visited an area near Livonia and Plymouth where 100's of trees exhibit similar declining symptoms. In general, the branches exhibit dieback, and/or sparse and stunted foliage. One consistent and quite conspicuous symptom is the extreme proliferation of shoots on the trunk (=epicormic shoots, suckers, etc.) (Fig. 39). These shoots tend to have very large, dense foliage and some of the shoots have already exceeded 4 feet of growth this year. Initially, when I inspected about 80 trees in a condo complex, all exhibited these symptoms and I suspected a herbicide problem. Further investigation of the area, particularly by my compatriot, Carl Dolhoff (retired MDA inspector), revealed that many other trees, whether in other apartment/condo complexes, or in street right of ways, all exhibited similar problems in at least a several square mile area. Obviously, this rules out cultural problems such as herbicide or fertilizer issues because the trees receive different attention. Ash borer has been found on a few trees but the presence of this insect does not appear to be a consistent correlation with the decline. But, an epicenter of ash yellows, local climatic issues or other incitants may be hypothesized as the culprits. One important management practice to be strongly considered by arborists, landscapers and homeowners is the cessation of planting ash trees, at least for this localized area.
I will be doing some testing, but if any of you have any clues as to the cause of the problem, I’d appreciate hearing from you. Also, if you have witnessed the same phenomenon at other locations around Michigan, I’d appreciate hearing from you as well at my email. It may be interesting to determine how widespread this particular problem is in the state.
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|Extensive bore damage on the trunk of a declining ash. (Fig. 38)||Declining ash with proliferation of shoots from trunk. This tree, like most others suffering from this malady, has a very healthy root system. The proliferation of shoots indicates tree compensation and "desire" for survival despite branch die back. (Fig. 39)||Close-up of larvae and the extensive damage to the vascular system of a declining ash. Photo wase taken in Sept. 2001 at one of Shade Tree Mechanic's Mike Myers' clients who allowed dissection of the tree for collection of samples, including insets and wood specimens for ash yellows analysis. Mr. Myers was apparently one of the first arborists to believe that an insect was probably a major contributor to the ash decline problem in SE Michigan. (Fig. 40)|
Ash Yellows Decline: August, 2001 Report:
I have received quite a few replies regarding the Ash problem in southeast Michigan. Thank you for your input. It seems from these responses that the ash problem is far more widespread than originally believed. In fact, in some areas, the incidence of ash decline is far exceeding the incidence of Dutch Elm Disease, which I consider to be of epidemic proportions in Michigan at this time. Carl Dolhoff, retired from MDA, in performing an informal survey, has found very severe decline in ash trees in the following areas: Livonia, Plymouth, Plymouth TWP, the city of Wayne, Westland, Garden City, Dearborn and Canton. Certainly in excess of 36 square miles are affected. I have also seen some signs of the same problem in other portions of Wayne, Oakland, Livingston and Washtenaw counties. I don’t think I would be exaggerating by suggesting that 1000's of trees are affected.
The Diagnostic Dilemma:
As suggested in earlier articles, one possible causal organism, whether primary or part of a complex, would be the ash yellows phytoplasma. The phytoplasma is considered an obligate parasite and cannot be detected by conventional laboratory culture techniques. It can be detected by other means such as ELISA tests and immunofluorescence microscopy. Unfortunately, during the summer months, it is practically impossible to detect the organism in foliage. The best time to detect the phytoplasma in foliage is in the early spring as the leaves are unfurling. Actually, the best location for detection of the phytoplasma is from vascular tissue (phloem) from the lower trunk of living trees. Thus far, I have not received any offers for the sacrifice of lower trunk tissue from living trees. If there is a possibility of collecting live tissue from the lower trunk of an affected tree, please contact me by email. I’ll provide advise on the collection and submission of the sample, and make certain it is tested. Otherwise, we will have to wait until spring for a possible survey of foliage.
Or Is It BORERS?
There is no question that borers are often associated with this problem. To my knowledge, of the samples that have been submitted to MSU, the red-headed ash borer, usually considered a secondary pest, has been found rather frequently. Unfortunately, many of the limb samples have been dead or near death. It would be advisable for the submission of live branch samples to check for primary insects such as clear wing moths, etc. Those limbs that exhibit green but stunted foliage would be good samples to collect for submission to the MSU entomologists.
Current Advice on Management:
Based on what we know so far, which isn’t a great deal, there are several management procedures we can advise. First, cease planting solid stands of ash; incorporate a diversity of other trees species in the landscape or right of way. The reason ash has been used so extensively in some areas is probably because of its ability to withstand adverse soil and site conditions, along with other factors such as rapid establishment and growth. Now, possibly because of several years of drought (1998, 1999, 2001) and several odd, but normal for Michigan winters, ash trees are probably being overwhelmed with some of these weak insects and diseases. The greater the incidence of the various diseases and insects in a given area, the greater the “pressure” on some of the moderately healthy but stressed trees.
For established trees, provide supplemental water for increased vigor. This cultural input is especially important during drought conditions. Moderate fertilization would also help to improve vigor in these trees. Please be advised that excess fertilizer or fertilizer without supplemental water may be stressful to these trees and exacerbate the problem. We will keep you posted of any further developments in this problem. (Back to top)
A cut-away section reveals borers hidden destruction. (Fig. 41)
David L. Roberts, Ph.D., Senior Academic Specialist
Michigan State University
College of Agriculture and Natural Resources
173 Giltner Hall, East Lansing, MI 48824-1101
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