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MAINE DEPARTMENT OF
CONSERVATION
Maine Forest Service
Forest Health & Monitoring Division
Links to: Issue 1 - May 13, 2002 Issue 2 - June 5, 2002
Summers like this are enough to make even the most stalwart entomologist/pathologist tear their hair out. Pest and host development went from early to behind with brief touches of seasonally warm weather. In many areas of the north it still looks like spring! Water levels are regaining ground with recent rains but the impact on pest development - well that's another story. Insect development is also more spread out within species than usual so take this into consideration in timing control measures. So with the stage set here we go with comments on current status. If in doubt and it's not here, refer to our first two seasonal issues - take two steps back and punt!
Insects
Arborvitae Leafminers (4 species) - Damage by one or more of these species may again be locally high. Where populations are high, large numbers of tiny moths (adults of these species) should be seen flitting around arborvitae foliage when disturbed from now through mid July. Some control may be achieved by treating ornamentals with diazinon at this time. New mines should be evident by early August and infested shrubs can be treated at that time with dimethoate (Cygon), acephate (Orthene), permethrin or chlorpyrifos. The most severe damage often occurs on commercial arborvitae varieties available in the ornamental trade. Some columnar forms are so severely damaged that only a green crown of foliage is left while native arborvitae nearby show only spotty damage.
* Balsam Gall Midge (Paradiplosis tumiflex) - It is still not too late to treat for this pest where a problem exists however, damaging populations are not expected in most stands.
*Balsam Twig Aphid (Mindarus abietinus) - The time for good control of twig aphid has past in most areas of the State.
*Birch Leafminers (Messa nana and Fenusa pusilla) - In our last issue these are listed as birch casebearer (our error). Mines of both are now in evidence in most areas and it is getting late for effective control this year.
*Browntail Moth (Euproctis chrysorrhoea) - Caterpillars should be searching for pupating sites this week. The small white moths with the characteristic brown tail will appear at lights in numbers within a couple of weeks. Watching for the moths is a good way to detect new infestations. Homeowners should be alert to the fact that the caterpillar hairs will remain toxic even after the caterpillars pupate. Residents of infested areas should take precautions for the next 4 or 5 weeks to avoid the hairs as much as possible - laundry should be dried inside and lawns mowed when damp to limit stirring up the toxic hairs.
*Bruce Spanworm (Operophtera bruceata) - Damage from this early season defoliator has not been observed this season in Maine even though it has been reportedly heavy in northern Vermont.
*Eastern Tent Caterpillar (Malacosoma americanum) - The nests (tents) constructed in the crotches of wild apple and cherry trees by this species have been extremely abundant and noticeable again this season. The large caterpillars are now wandering in search of pupation sites. New tents which are just starting on old field and roadside cherry are more likely those of cherry scallop shell (the looper Hydria prunivorata) or the ugly nest caterpillar (Archips cerasivovanus).
*Fall Webworm (Hyphantria cunea) - Emergence of the small white moths of this species has begun in much of southern Maine. Tents and defoliation can be expected to run high again this season in many of these areas in July and August. Treatment as soon as the larvae emerge in early to mid July should alleviate the problem. Bt (Dipel), carbaryl (Sevin), diazinon and acephate (Orthene) are registered for this insect.
*Gypsy Moth (Lymantria dispar) - Populations are up in many areas of southern Maine and defoliation is already evident in infested stands in Androscoggin, Cumberland and York counties. Caterpillars show a great range in size but most are too large for effective control to prevent defoliation this season. Hopefully, disease will significantly reduce populations.
*Hemlock Looper (Lambdina fiscellaria) - Larvae are now out and visible in infested stands. Populations in York county (Ogunquit, Wells and York) are running low to moderate but infested trees were rough to start with from previous defoliation and drought so damage may look worse. Populations in Hancock and Washington county, mostly around water bodies, are running moderate in many areas with 15-35 larvae per branch. In nearly all areas checked, new foliage development this season was ahead of looper development. Treatment with Bt should still be effective if applied soon.
*Hemlock Woolly Adelgid (Adelges tsugae) - Keep a look out for this species and report suspected infestations to Don Ouellette, Insect & Disease Laboratory, 50 Hospital Street, Augusta, ME 04330, Tel. 207 287-2431 or e-mail don.ouellette@state.me.us.
Larch Sawfly (Pristiphoraerichsonii) - Larch sawfly larvae should now be visible and feeding.
*Pine Spittlebug (Aphrophora parallela) - Spittle masses on conifers, especially pines, are very abundent this season. Drip from the nymphal activity often approaches the level of a light drizzle in white pine stands.
*Satin Moth (Stilpnotia salicis) - Larvae of this species should now be active, although we have received no reports so far.
*Ticks (various) - Still active and biting. They're farther north than you think! Detailed information on the tick and Lyme disease status for Maine is available upon request.
*White Pine Weevil (Pissodes strobi) - Don't forget corrective pruning of infested leaders which should soon wilt and become evident
*Yellowheaded Spruce Sawfly (Pikonema alaskensis) - Populations appear to be low but control could still achieve some protection of ornamentals.
Diseases and Injuries
*Ash Leaf and Twig Rust (caused by Puccinia sparganiodes) - Ash leaf and twig rust caused light to moderate defoliation of white ash in portions of many coastal communities in 2001, and moderate to severe defoliation to trees in the Kittery/Wells/York/Ogunquit areas. As a result many ash trees are pushing only limited new growth as the result of stem tissue killed by last year's infection. This symptom is especially pronounced this spring in the Wells/Ogunquit area.
It is a bit too early to be certain, but readers should expect to see another round of ash defoliation due to this disease later this summer. Most defoliated trees will eventually recover, but it may be several years before trees appear normal.
Ash, Maple, and Oak Anthracnoses (caused by Apiognomonia errabunda, Kabatiella apocrypta and Discula quercina respectively) - These diseases, which cause irregular tan or brown spots of blotches on leaves often followed by defoliation are expected to be more common than usual this year. Ample spring rains have provided for multiple infection periods. Most trees defoliated by these diseases will refoliate later this summer. Sprays at this time are not recommended.
Bud Abortion of Balsam Fir (caused by low ambient air temperatures prior to budbreak) - This symptom is relatively uncommon around the state this spring.
Chestnut Blight (caused by Cryphonectria parasitica) - This disease, which was introduced to North America around 1900 on nursery stock of oriental chestnuts, subsequently spread into Maine and quickly destroyed our native American chestnut resource. A few infected trees persist, often sprouting from old stumps, and occasionally a seedling will grow to considerable size in the woods before succumbing to the disease. American chestnut trees planted as landscape specimens also frequently attain considerable size before fatal infections develop.
Recently considerable interest has been expressed in support of an effort to reintroduce the American chestnut into Maine forests. The American Chestnut Foundation (TACF) began work several decades ago to breed resistant American chestnuts, and is now several breeding generations into that project. The Maine Chapter of TACF has more recently begun work to introduce genes from native Maine chestnut into TACF's partially resistant hybrids, and partially resistant trees that are fifty percent Maine American chestnut are already planted out in several breeding orchards at various sites in Maine.
It is expected that breeding for the fully resistant American chestnuts with good timber form will be completed by TACF within a decade, and resistant trees with Maine genes created by the Maine Chapter will follow in another decade or two.
Heavy Seed Production - While 2002 is not an unusually heavy seed year, cones are very prominent on most balsam fir trees and countless individual red maple trees have set heavy seed crops this spring as well. Most of the red maple seeds have already dispersed, leaving trees looking quite thin.
Stillwell's Syndrome (associated with Armillaria spp.) - Stillwell's syndrome ("red fir"), a symptom associated with fir mortality which was common in Maine forests in the 1980's is beginning to reappear. Balsam fir often turns bright brownish red as it dies, and is conspicuous among healthy, green trees in forest stands when viewed at a distance.
Most trees with Stillwell's syndrome are infected by Armillaria spp.,which causes a disease known also as shoestring root rot. Removing the bark from the base of infected trees reveals the white mycelial mats of the shoestring root rot fungus.
Armillaria infection usually causes the death of trees stressed by other factors. In the 1980's, spruce budworm feeding was often a primary stress factor. But today's fir which exhibit Stillwell's syndrome have probably been weakened primarily by drought, but also in some circumstances by ice damage, road salt, overly wet sites, and balsam woolly adelgid infestation.
Sudden Oak Death (caused by Phytophthora ramorum) - This disease, which causes mortality of oaks and tanoaks in California and southwestern Oregon, has received much play recently in the national media. While sudden oak death is not known to occur in the United States outside of those two states, our northern red oak is known to be susceptible.
The causal fungus affects not only oaks, but also species of Rhododendron and certain other trees and shrubs, so there is considerable potential for the spread of this disease on infected landscape stock.
Accordingly a national survey is planned to determine whether and to what extent this disease may have spread from the west coast. The Maine Forest Service will participate in that survey, and we will relay our findings to you via this newsletter at a later date.
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Insect and Disease Laboratory, 50 Hospital Street, Augusta, Maine
04330-6514
Phone (207) 287-2431, Fax (207) 287-2432.
Compiled by Richard
G. Dearborn and Clark A. Granger
02-3 Forest Health & Monitoring Division Augusta, Maine
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