Forest & Shade Tree - Insect & Disease Conditions for Maine

April 17, 2009

Welcome to the 2009 growing season, and to this series of the Insect and Disease Conditions reports!  This year we will be surveying again for several of the exotic pests which are potential threats to Maine forests, but have not yet been found here.  In addition, we will also provide updates on the new and long-standing pest problems that do occur in the state.

Overall, Maine’s forests are entering the 2009 growing season in exceptionally good condition.  But, with over 17 million acres of forest land to monitor, successfully keeping our forests healthy requires a cooperative effort.  A large portion of the insect and disease pests that are examined by the staff at the Insect and Disease Lab come from landowners, foresters, growers, green industry representatives, and the general public.  So, without your involvement in detecting pests and alerting us to these problems, our effectiveness would be significantly reduced.  With that in mind, once again we ask you to be vigilant, to make timely observations and let us know what you are seeing whenever you’re willing to share.  Your efforts are always greatly appreciated, and we wish you all a successful and productive growing season!

Laboratory Hours

Our business hours for 2009 will be 7:30 a.m. to 4:00 p.m. Monday through Friday, except for holidays.  However, due to a very busy field schedule, we may not be able to staff the Insect and Disease Lab at all times. So if you call and receive no answer, please call back another time. And if you plan to visit the Lab, you may wish to call ahead just to make sure someone will be present to meet with you. 

If you have questions on insect and disease pests of trees, you can now submit a clinic form directly on-line.  We will also accept samples mailed in to our Lab in Augusta.  And, although our street address and location remains the same (50 Hospital Street, Augusta), our mailing address is now 168 State House Station, Augusta, 04333-0168.  Lastly, we have attached the following items to this report for your use:

Advice and Technical Assistance Sheet.

Insect & Disease Diagnostic and Report Form.

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Tree Owner's Manual Available

The Tree Owner’s Manual is now available to property owners seeking information about caring for one of the most valuable assets on their land—its trees. The U.S. Forest Service created the Tree Owner’s Manual to answer common questions about tree care, from planting, fertilizing, and pruning to troubleshooting signs of damage, injury, and disease. The manual also lists numerous organizations and sources of more information for keeping trees healthy and growing. The booklet is available in a simple black and white format that is easy to download and inexpensive to reproduce. The Forest Service will help organizations or businesses customize the cover of the manual with their own logo. To download a copy of the Tree Owner’s Manual, or to request a customized version with a logo on the cover, visit the Tree Owner's Manual Web page

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Maine Arbor Week: A Great Time to Celebrate Trees!

Since 1978, Maine has celebrated Arbor Week during the 3rd full week in May. Arbor Week is a time to reflect upon an enormous resource we have here in Maine – our trees and forests! They provide us with numerous environmental, economic, aesthetic, and social benefits. This year, Arbor Week falls from May 18th thru May 23rd.

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Quarantine News

Maine has five forestry-related quarantines:  (1) Ribes spp. (currants and gooseberries) because they are alternate hosts for white pine blister rust, (2) gypsy moth, (3) European larch canker, (4) hemlock woolly adelgid and (5) pine shoot beetle.   The quarantine on Ribes prohibits planting, possessing or propagating currant or gooseberry plants in some parts of the State and prohibits the species European black currant, Ribes nigrum, and its cultivars throughout the State.  The four other forestry-related quarantines restrict the movement of certain forest products that have the potential to spread specific tree pests or diseases.   Regulated material may move freely within their respective quarantine zones, but must go to facilities with compliance agreements and may require inspection if they are moved outside of the quarantine zone.  The compliance agreements require certain practices of the receivers to help reduce the risk of spread of the target insect or disease organism. 

The following is a rundown of recent changes to the quarantines:

Gypsy Moth:  The quarantine boundary for gypsy moth was adjusted in 2008 to includeT3 R4 BKP WKR and Pierce Pond Townships, both in Somerset County.  The townships of T6 R10 WELS and Trout Brook in Piscataquis County (both part of Baxter State Park’s Scientific Forest Management Area) and Mount Chase in Penobscot County have been recommended for inclusion in the quarantine at the next revision. 

European Larch Canker:  Although nothing has changed in the quarantine rules in 2008, larch canker in Maine was found in the town of Brunswick (Cumberland County).  This location is outside the current State and Federal quarantine boundaries, which have been in place since 1982.  A survey of approximately 700 acres surrounding the newly found infestation was conducted, with 222 larch trees located.  Maine Forest Service personnel, with the assistance of personnel from the USDA Forest Service, Durham, N.H., completed individual tree inspections of the larch found. Thirty-two of the 222 larch were found to be infected with the larch canker pathogen.   No stem cankers were found.  All the infected trees were located on the fairways of a golf course, and all are European larch or European larch hybrids.  Eradication of the diseased trees was completed in December of 2008.  Annual re-surveys of the remaining larch will be ongoing, to ensure that the disease has been eliminated from this location.

If you have any questions regarding forestry-related quarantines or moving or receiving regulated material, please contact Allison Kanoti at the Maine Forest Service, or (207) 287-3147. Maps and lists of quarantined towns and information about all the forestry-related quarantines in Maine can be found at our Website. Thank you for your continued cooperation in keeping these forest pests and diseases contained.

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Northeastern Forest Health Field Workshop

June 2 through 5, 2009

This workshop is aimed at natural resources professionals interested in forest health and will be held on June 2-5 at the Schoodic Educational and Research Center (SERC) in Winter Harbor, ME.  Two days of forest health discussions will take place in the woods around SERC. The topic for Wednesday’s field trips is “Using Silviculture to Reduce Risk from Pests” and will focus on spruce/fir, American beech, and eastern white pine forest types. Thursday’s field trips will examine the “Forest Health of Acadia National Park” on Mount Desert Island and will focus on invasive species, air pollution, and monitoring. The workshop has been previously called the "Northeastern Forest Pathology Workshop", but the name has been updated to reflect the greater breadth of topics that are covered. The workshop is being co-sponsored by the University of Maine School of Forest Resources, the Cooperative Forestry Research Unit, Maine Forest Service, and the Maine Division – Society of American Foresters.

If you are interested in attending please register by May 1st from the workshop Website.

Dates: June 2-5, 2009



Regular: Each field trip is $50 or $100 for both.
Maine SAF Members: The cost is $35 per field trip or $70 for both
Price includes transportation, lunch, and snacks.
Register On-line


Total cost for three nights of lodging plus meals (breakfast and dinner on W&Th, breakfast and break on F)
$155.50 per person for a 2 bedroom apartment
$200.50 per person for a single bedroom apartment.
Please provide your own toiletries.
Reservations for lodging can be made by calling SERC: 207-288-1326

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Early Season Guide to Pest Management

The following table should assist you in the early season planning process.  Remember that this is just a guide and that conditions will vary.  Many pests may be managed with several other suitable products not listed here, but registered for use in Maine.  This chart reflects those products that should be readily available and effective, but not to the exclusion of others that may be suitable. Information on any entry preceded by an * may be available on our website or can be requested by calling or writing to the Insect and Disease Laboratory, 168 State House Station, Augusta, Maine 04333-0168, Phone (207) 287-2431, Fax (207) 287-2432.

Insect or Disease

Cultural Controls

Chemical Controls

Apple Scab

Remove any fallen leaves not raked last autumn; plant resistant crabapples such as ‘Adams’, ‘Baskatong’, ‘Beverly’, ‘Bob White’, ‘David’, ‘Dolgo’, ‘Donald Wyman’, ‘Liset’, ‘Red Jewel’ and ‘Sugartyme’. Other varieties of apple that are resistant to scab include Liberty, Pristine, Jonafree, Freedom, Redfree, Crimson, Enterprise, and William’s Pride.

Propiconazole (Banner), Thiophanate methyl (T-Methyl), Chlorothalonil (Daconil), or Mancozeb (Dithane, Fore, Ziram) from bud break every ten days during wet weather. Captan, Manzate, and Polyram are also effective.

Ash Anthracnose

Before budbreak, remove any fallen leaves not raked last autumn.  Compost the leaves well away from ash trees.

Propiconazole (Banner), Chlorothalonil (Bravo, Daconil, Mainsail WDG) at budbreak, and again 10 to 14 days later.

*Ash Leaf Rust

None which are practical and effective. 

Mancozeb, chlorothalonil (Daconil), or Thiophanate methyl (T-Methyl), applied at budbreak and repeated 2 to 3 times at 10-day intervals.

*Balsam Gall Midge

Diazinon or chlorpyrifos (Lorsban**) late May to early June.

*Balsam Shootboring Sawfly

Lorsban 4E** or Diazinon AG500 3 times at 5 day intervals during the 2 weeks following the observation of activity of adults (mid-late April) or in the two weeks prior to normal balsam twig aphid spray dates.

*Balsam Twig Aphid

Diazinon**or chlorpyrifos (Lorsban**) at bud break.

*Birch Casebearer

Malathion or carbaryl (Sevin) applied after most or all of the cases have moved to opening buds.

Black Knot of Peach, Plum, and Cherry (UMO Fact Sheet)

Prune and destroy knotted twigs and branches.

Thiophanate methyl (T-Methyl or Fungo Flo) or chlorothalonil (Daconil) when trees are dormant and twice again at three week intervals after budbreak.

*Browntail Moth

Clipping of overwintering webs is only effective prior to the time larvae beginning actively feeding on emerging foliage (mid to late April).

The use of pesticides is a complex issue requiring professional assistance and there are restrictions on treating near water.  Call for more information. 

*Bruce Spanworm

Emerges early as buds begin to swell on northern hardwoods, especially beech. Larvae bore into buds. Controls not usually recommended.

Cyclaneusma Needle Cast of Scotch Pine

Use disease free planting stock; remove non crop Scotch pines from area.

Chlorothalonil (Bravo or Daconil) prior to bud break and immediately after wet periods throughout the growing season.

Diplodia Tip Blight

see Sphaeropsis Shoot Blight

see Sphaeropsis Shoot Blight

Dogwood Anthracnose (USDA How-To)

Remove any fallen leaves not raked last autumn; fertilize trees; prune out dead twigs and suckers; plant Chinese or Japanese dogwood instead of native flowering dogwood.

Chlorothalonil (Daconil), Thiophanate methyl (T-Methyl, Fungo Flo), Propiconazole (Banner), or Mancozeb (Dithane, Fore) at bud break and again three times at three week intervals.

Dothistroma Needle Blight

Copper sulfate (Kocide) or Thiophanate methyl (T-Methyl)

Dutch Elm Disease

Plant disease resistant elms; eliminate all potential beetle breeding elm material within 700 feet of trees to be protected.

Onyx (bifenthrin) or chlorpyrifos (Lorsban**) for beetle vector control on the lower 9’ of trunk.

*Eastern Tent Caterpillar

Prune out egg masses on twigs prior to hatch; remove and destroy small tents as they develop (late April-early May)

Acephate (Orthene), carbaryl (Sevin), cyfluthrin or Bt on warm days when larvae leave tents to feed.

*Fall Cankerworm

Acephate (Orthene), Bt, carbaryl (Sevin), cyfluthrin (Tempo) applied while larvae are small (late May-early June on boxelder in Aroostook County).  Early to mid May on elm and oak in southern Maine.

*Gypsy Moth

Scrape egg clusters from tree boles and larger branches into a container and destroy them.  Complete before egg hatch (late April).

Acephate (Orthene), Bt, carbaryl (Sevin), cyfluthrin (Tempo), or diflubenzuron (Dimilin**) when larvae are actively feeding (early June).

Hawthorn Leaf Spot, Mt. Ash Leaf Spot

Remove any fallen leaves not raked last autumn; plant resistant varieties such as Crataegus crus-galli.

Thiophanate methyl (T-Methyl or Fungo Flo), Chlorothalonil (Daconil), or Mancozeb (Dithane, Fore) as leaves unfold and at two week intervals until dry weather.

*Hemlock Woolly Adelgid

Watch for signs of infestation and report immediately.

Call for information.

Horse Chestnut Leaf Blotch (UMO Fact Sheet)

Remove any fallen leaves not raked last autumn.

Thiophanate methyl (Fungo Flo) or chlorothalonil (Daconil) at bud break and twice more at 14 day intervals.

**Larch Casebearer (USDA FIDL)

Carbaryl (Sevin) or cyfluthrin (Tempo) applied after most cases have moved to the expanding needle clusters (late April to early May).

Maple Anthracnose (USDA FIDL)

Before budbreak, remove any fallen leaves not raked last autumn.  Compost the leaves well away from maples.

Thiophanate methyl (Fungo Flo) at bud break and twice again at 10-14 day intervals.

Peach Leaf Curl (UMO Fact Sheet)

Chlorothalonil (Bravo) or Ferbam (Carbamate) or Ziram applied as full coverage spray when trees are dormant.

*Pear Thrips (USDA Pest Alert)

Controls and timing not well understood.  Thrips are active on expanding maple.

Pine-Pine Gall Rust of Jack and Scotch Pine

Prune rust galls from lightly infected trees; rogue heavily infected trees from plantations before May 1.  Use disease free planting stock.

None at this time.

Rhabdocline Needle Cast and Swiss Needle Cast of Douglas-Fir

Rogue severely infected trees from plantations before May 1.

None at this time.

*Satin Moth

Treat infested poplars and willow in mid to late May with Bt, carbaryl (Sevin) or cyfluthrin (Tempo).

Sirococcus Shoot Blight of Spruces

Prune out affected twig tips by mid-summer, and destroy.

Chlorothalonil (Daconil, Bravo), at bud break and again 10 to 14 days later.  The second application should be applied sooner if wet weather conditions prevail.

Sphaeropsis Shoot Blight of Red, Scotch, and Austrian Pines

Use disease free planting stock; remove non-crop-tree hard pines from area. Prune and burn lower, heavily infected and dead branches.

Chlorothalonil (Bravo), copper sulfate (Kocide), or Thiophanate methyl (T-Methyl, Topsin) at bud break and again when shoots are half grown.

*Spruce Gall Adelgids (eastern, Cooley)

Prune off and destroy new developing galls in mid to late June.

Treat infested trees just prior to bud break with dormant oil, carbaryl (Sevin) chlorpyrifos (Lorsban**) or imidacloprid (Merit). Controls can also be applied in the fall.

Spruce Needlecast of White and Colorado Blue Spruce (Rhizosphaera kalkhoffii) (UMO Fact Sheet)

Prune, remove, and destroy the most heavily infected, lower branches on larger trees.

Chlorothalonil (Bravo, Daconil), or copper sulfate (Bordeaux mix) as buds break and again 10 days to two weeks later.

*Ticks (UMO Fact Sheet) (Tick ID, MMCRI)

Watch for ticks throughout the field season (April-November).  Avoid high risk areas if possible, inspect yourself daily and remove ticks and use repellents as directed.

Compounds containing DEET can be used as repellents.  Those containing the toxicant permethrin can be used on clothing as directed.

*Viburnum Leaf Beetle (Cornell Site)

Where possible, prune off any twigs with scabby, egg-filled holes prior to  May 1st.

Watch in mid - late May)- for developing larvae and treat with acephate (Orthene), carbaryl (Sevin), or chlorpyrifos (Lorsban**) or imidacloprid (Merit).

* White Pine Blister Rust

Prune cankered lateral branches from trees and excise stem cankers by removing bark at least four inches above and below and two inches either side of discolored bark.  Remove species of Ribes from within 1000 feet of white pine forests or plantations.

None at this time.

*White Pine Weevil

Refrain from planting white pine or spruce for reforestation in open areas, on heavy clay soils, or on heavily sodded fields. Correctively prune damaged trees to establish new leaders.

Apply control in the spring once there have been several days above 60 degrees Farenheit. Use Pyrenone Crop Spray, Astro, Onyx, Talstar or Dibrom 8 at 14-20 day intervals until June.  Commercial Forest and Christmas Tree Plantations: Dimilin** or Lorsban**.

*NOTE: These recommendations are not a substitute for pesticide labeling. Read the label before applying any pesticide. Pesticide recommendations are contingent on continued EPA and Maine Board of Pesticides Control registration and are subject to change.

Caution: For your own protection and that of the environment, apply the pesticide only in strict accordance with label directions and precautions.

**Restricted-use pesticide may be purchased and used only by certified applicators.

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*Asian Longhorned Beetle (Anoplophora glabripennis) – The Asian longhorned beetle has not been detected in Maine, however please become familiar with how to identify it and the damage it causes (you can find links to identification tools are linked on our Website).  As reported last year, the Asian longhorned beetle was found in Worcester, MA in August of 2008; it has been there for at least 10 years.  Each year there are thousands of opportunities for introduction of this and other exotic insects on recreational firewood (brought to campgrounds or second homes).  In a survey conducted by our division in and around Acadia National Park last summer, thirteen percent of campers surveyed sometimes brought firewood with them AND came from states or provinces known to have infestations of Asian longhorned beetle or emerald ash borer, two of the most serious invasive forest pests in eastern North America. 

If you think you see an Asian longhorned beetle, please catch it or take a photo and send it to us.

*Balsam Gall Midge (Paradiplosis tumifex) - Balsam gall midge populations were on the rise last year so Christmas tree growers should be checking their plantations this spring for the midges. The balsam gall midge larvae feed on the new foliage and cause the needle to deform and form a gall around the growing larvae. After the larvae finishes feeding and drops to the ground at the end of summer, the damaged needles also fall off.  Populations can get high enough so that the tips of branches are denuded.  This makes Christmas trees and wreath brush unmarketable for a few years until the foliage fills in.

In mid to late May watch for small orange midges, they are often easiest to see in the early evening when the breezes die down.  Treatment is applied approximately two weeks after adults have been seen in large number (late May to early June) as the new needles flare and begin to flatten. 

*Balsam Shootboring Sawfly (Pleroneura brunneicornis) - This sawfly is usually less abundant in odd numbered years and we did not have any reports of outbreaks last year.  Adults are active at the end of April flying around the fir trees.  The females lay eggs on the buds and larvae feed before the buds expand.  The resulting damage appears as a little “button” of foliage with a hollow stem – in May you can sometimes find the larvae still in the shoot.  This sawfly damage can be mistaken for frost damage.  Damage from light infestations can be pruned off.

*Balsam Twig Aphid (Mindarus abietinus) – Balsam twig aphids appear early in the spring and suck the juices from the tender new foliage of fir trees.  This feeding causes twisting and distortion of the foliage.  It does not harm the tree but makes it less attractive for Christmas tree sale.  Twig aphid tends to be a perennial problem for Christmas tree growers.  Check for aphids in May before budbreak; if trees were damaged last year they may need to be treated this year as the population builds up from year to year.

*Browntail Moth (Euproctis chrysorrhoea) – The browntail moth winter survey has been completed for 2009.  We found very high numbers of webs at the southern end of Merrymeeting Bay in the towns of Bath, Bruswick, West Bath and Topsham. The southern part of Bowdoinham and Bustins Island off Freeport also has high numbers of webs. Webs in individual trees or a few trees were found from Portland to Freeport and in Augusta.

Overwintering survival of the larvae is being checked as this newsletter goes to press. Most of the webs brought in to the lab have emerging larvae so the cold January temperatures did not do them all in. 

Browntail moth larvae feed on the emerging foliage of oak, apple, birch, cherry, hawthorn, rose and other hardwoods.  They emerge from their overwintering webs starting the end of April, even before the buds have broken.  They continue to feed on leaves and molt their hairy skins through June when they pupate leaving their last hairy skin behind.  Besides defoliating trees and causing branch dieback and tree mortality, all those hairs make many people itch.

Pruning out webs and destroying them (drop them in soapy water) may eliminate the problem if all the webs are within reach. Clipping should be completed by the end of April and insecticide applications (if warranted) should be made during the month of May by a registered pesticide applicator.  There are specific regulations for controlling browntail moth near coastal waters.  Be sure to check on the current Board of Pesticide Control regulations before treatment.

*Eastern Tent Caterpillar (Malacosoma americanum) – The first eastern tent caterpillars will be out on the branches of crabapple and cherry trees by the time you receive this publication. Look for the webs in the branch crotches and remove the webs and caterpillars before they get too big.  Although the tents are unsightly, these insects rarely harm the trees.

*Gypsy Moth (Lymantria dispar) – Egg mass surveys conducted this fall and winter within the generally infested area indicate that gypsy moth populations remain at low levels.  Trapping to monitor northward spread of this insect will be conducted starting in July of this year.  This will include more intensive trapping around the population detected last year in T6 R10 WELS to determine the extent of that population.

*Hemlock Woolly Adelgid (Adelges tsugae) –Eggs and crawlers, the most easily spread stages of this insect, are currently abundant in infested areas of southern Maine.  Use caution when coming from potentially infested stands, as the minute crawlers are barely detectable to the naked eye and can survive for several days (more than 2 weeks in one study) without food.  All hemlock woolly adelgids in northeastern North America are female; because of this and their tremendous reproductive capacity, one crawler has the potential to establish a new infestation.

Although this was a cold winter, it was not cold enough that we should expect decreasing hemlock woolly adelgid populations in infested portions of the state.  Across nine untreated sites hemlock woolly adelgid had an average overwintering mortality of 68 percent.  About 90 percent overwintering mortality is thought to be required to maintain stable populations of this insect.  Continued population expansions are expected in 2009.  If you suspect you have found hemlock woolly adelgid, please report your findings to the Lab.

Overwinter HWA mortality 2003 through 2009 and
Maine statewide (December through February) winter climate summary 2003-2009

Overwinter Mortality

Winter Climate Summary






Departure from Normal (°F)*

Rank (Since 1895)**







40th of 109







50th of 110







102nd of 111







82nd of 112


No samples collected


68th of 113







21st of 114

*1971 to 2000 Normals     ** 1 = Coolest       (Data from:

*White Pine Weevil (Pissodes strobi) - Control of white pine weevil should be underway in southern parts of the State by the time you receive this publication.  The adults lay eggs and the larvae feed on the terminal leader of pine and spruce in early spring.  On ornamentals, covering the leader with a nylon stocking secured with a twist tie can block the female from laying eggs. Remove the covering before the leader begins to elongate. This of course is not practical on a large scale and chemical control may be warranted for Christmas tree or timber plantations.  See chemical control recommendations listed above.

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Diseases and Injuries

Winter Desiccation – This past winter was considerably colder than the previous year, and trees in some areas throughout the state are showing substantial winter injury.  Exposed conifers, in particular hemlocks, white pines, and junipers, are the most severely affected.  Winter desiccation, or drying, occurs when the foliage is exposed to cold temperatures and high winds, while the ground remains frozen.  The inability to replace the moisture lost from the foliage results in winter-burn (image).  These symptoms and the damage caused are made even more severe if roadside deicing chemicals have been splashed or carried from wind-driven mists.  The damage is commonly seen affecting trees along the major roadways, and especially those growing on low or wet sites, where roots are shallow, and the ground was deeply frozen.  While damage from winter desiccation can adversely affect tree growth and vigor, most trees will recover quickly when new foliage begins to develop this spring.  If the damage was severe enough to kill buds, recovery will be significantly slower.  A check of bud vitality (branch tips and buds should show as bright green under the bark or bud scales) can give a rapid indication of the severity of damage.

White Pine Blister Rust (Cronartium ribicola)We have already received several inquiries this spring from homeowners conveying an interest in growing currants, Jostaberries, and gooseberries (Ribes species) as a horticultural crop.  The importation, possession, planting, and culture of any species of  Ribes is prohibited by law in the quarantine area (approximately the southern half ) of Maine, and the importation, possession, planting, and culture of any Ribes nigrum (European black currant) or its varieties or cultivars is prohibited throughout the entire state.  A list of the quarantined towns and a description of the law is available on our website, as reported under the Quarantine section of this Insect and Disease Conditions Report.  Ribes species act as a required alternate host for the white pine blister rust disease, the one of the most destructive diseases of white pines in North America.  Ribes plants found growing within the quarantine zone are subject to confiscation and destruction by state authority.

Protecting white pines by conducting Ribes eradication efforts have been ongoing for over eighty years in the quarantine zone.  Where eradication efforts have managed the Ribes population, incidence of the disease in white pine has been shown to be reduced by at least fifty percent.  Early spring is the optimum time to survey white pine stands to find native currant and gooseberry plants.  The disease is most damaging in young regeneration and in sapling to pole-sized timber.  By uprooting or treating the Ribes with herbicides, subsequent infection of white pine can be prevented.   Most common species of Ribes in Maine are among the very first woody plants to break bud and “green up” in the spring, (by mid- to late April in southern Maine), making them easily visible in woods and brush thickets where they grow.

Control need not be done this early in the season, but identification of individual Ribes plants, or concentrations of plants, is much easier now than later in the season, when all other plants are in full leaf.    For specifics of the white pine blister rust disease, and of the current quarantine regulations affecting Ribes species, please call or write the Insect and Disease Lab, or check the MFS, Forest Health and Monitoring Website.

Common Foliage and Needle Diseases – The early spring is when initial infections by several foliage and needle diseases occur.  The common anthracnose diseases of hardwoods, including maple anthracnose (image) and ash anthracnose, sometimes cause leaf browning by mid-summer, and premature leaf fall in autumn.  Spring seasons with unusually long or frequent wet periods can initiate a high level of needle disease such as spruce needlecast of white and Colorado blue spruce, and tip blight of pines.  Both of these needle diseases have been quite severe in recent past years.

Applications of fungicide are usually not necessary in most years; normal spring weather, with good drying days between rain showers is most often the rule.  However, if trees were severely infected last spring, and forecast conditions indicate an especially wet season in your area, fungicide applications may be prudent. Fungicides that control these diseases are protectants, and must be applied before leaf or needle infection takes place.  This requires applications of the fungicide at the time of budbreak (usually about the first week in May for hardwoods, and two or three weeks later for pines and spruces).  As leaf and needle tissue continues to grow and expand, an additional one or two applications of fungicide is required to cover the new tissues.  Management programs should remain flexible; if extended periods of wet weather persist, the number of applications can be increased, or timing between applications can be shortened.  If early spring conditions are dry, reduce the number of recommended applications or lengthen the time interval between recommended applications.  Always refer to the product label, and never apply more frequently or in higher doses than stated on the label.  Refer to the Early Season Guide to Pest Management for more specifics on products and timing of applications.

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Conditions Report No. 1, 2009
Maine Forest Service
Forest Health and Monitoring Division