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Image: (Left) The percentage of normal precipitation in August 2025 compared to the normal precipitation averages from climate records dated 1991-2020; (Right) Drought conditions for Maine as of September 9, 2025. Source: Northeast Regional Climate Center, U.S. Drought Monitor.
Globally, August 2025 is the third hottest on record with the hottest and second-hottest Augusts occurring in 2023 and 2024, respectively. In Maine, August temperatures ranged from normal to slightly above average, with an overall average temperature of 64.8°F – roughly 1.8°F warmer than normal historical temperatures. Mid-August brought record-breaking high temperatures in Caribou at 94°F, and Millinocket at 95°F, with a heat wave that carried through much of the state. Temperatures are expected to return to normal through September and are likely be above average from October through January (National Weather Service).
Total rainfall statewide was below normal in August with an average total of only 1.93 inches, which is approximately 1.58 inches less than historic averages for the state in August. As the pattern of reduced rainfall this summer continues into September, we are continuing to see consistent drought conditions for much of the state. At the end of August, an estimated 86% of Maine was experiencing some level of drought, and approximately 53% of those areas affected were under severe drought conditions. With a continued rainfall deficit, drought in the southern two-thirds of Maine will persist into September, but may decline over the coming months as rain totals are expected to be close to normal in October and November (National Weather Service). Soil moisture is forecasted to be below 70% percentile for much of the state through October (U.S. Drought Monitor).
Severe drought conditions may lead to yellowing foliage, premature leaf drop, dry soil, low water levels in streams, reservoirs, and wells, and, at times, can lead to increased fire danger. Maine Forest Service (MFS) Rangers continue to recommend checking the daily Wildfire Danger Report and consult with local fire officials before conducting any open burning.
Black Giant Ichneumonid Wasp (Megarhyssa atrata)
The black giant ichneumonid wasp, Megarhyssa atrata, is a visually striking wasp native to Maine, notable for its large size and exceptionally long ovipositor. Like the species released for biological control of emerald ash borer, this wasp is a parasitoid. However, this native species is significantly larger and targets the larvae of wood-boring horntail wasps, another family of wasps known for their large size.
Though this specimen was found motionless on the side of the road in midcoast Maine, observing the oviposition process can be something to behold. This involves a complex series of movements by which the two long sheaths on either side of the central stylus are drawn up under the female’s perched body and wood dissolving secretions are produced to aid oviposition. From there, the female uses her thread-like ovipositor to carefully reach deep into tree trunks where the target host resides.
The unique and extraordinary ovipositors of M. atrata make them one of the more remarkable insects found in Maine’s forests. Observing this species provides a glimpse into the complex interactions that maintain forest health. As natural regulators of wood-boring insect populations, they play an important role in preserving the balance of woodland ecosystems.
Image: The black giant ichneumonid wasp is one of the larger wasp species found in the state.
Browntail Moth (Euproctis chrysorrhoea)
In late summer, browntail moth caterpillars have one main task: craft their winter webs. By spinning strong silk around a few leaves, these caterpillars create a water-tight shelter for themselves that they rest inside during the winter. Their meticulous work can be difficult to see this time of year while the majority of the leaves remain on the trees. Browntail caterpillars will continue to build their winter webs until shorter sunlight days and colder temperatures encourage them to hide inside their webs to survive the cold season. These winter webs are best detected on sunny days in the winter; with no other leaves to block your view, the sunlight helps to reflect the white silk of the browntail webs.
Image: (Left) Young browntail moth caterpillars in September beginning to create their overwintering webs for the winter season; (Right) A completed browntail moth winter web. Note the silk tying the web firmly to the branch.
Around this time of year, we often get reports of large, conspicuous looking webs in deciduous trees. Although these webs can look alarming, they are not from browntail moth, but created by a native insect, fall webworm (Hyphantria cunea). Fall webworm caterpillars are generally not a forest health concern, nor do they have toxic hairs. Learn more about the difference between browntail moth webs and fall webworm webs in our browntail moth bulletin from August: “Webs in Late Summer: From a Friend or Foe?”
It is unclear how the current ongoing drought conditions may influence declining browntail moth populations. Typically, periods without rain can limit the spread of browntail moth pathogens such as Entomophaga aulicae, a fungus that is specific to lepidopteran hosts. However, it will be difficult to determine the extent of the impact from extended drought conditions until we begin conducting our winter web survey.
Emerald Ash Borer (Agrilus planipennis)
Since 2019, MFS has been releasing parasitoid wasps for the long-term management of emerald ash borer (EAB) in the forests of Maine. These are tiny, non-stinging members of the order Hymenoptera, and they specialize in EAB. In most cases, they will not keep the mature trees already in the forest alive, but there is evidence from other states that have had EAB longer than we have that these wasps provide protection to the seedlings and saplings as they grow. We are attempting to release them in as many areas with EAB as possible so that they can eventually spread throughout the state, allowing ash to remain in Maine’s forests.
Image: From left to right, emerald ash borer parasitoids: Spathius galinae, Tetrastichus planipennisi, and Oobius agrili.
As of 2025, we have released these parasitoids in 20 sites throughout the range of EAB. Of the ten sites that are at the stage where we can start monitoring for their establishment, we have recovered one or both of Spathius or Tetrastichus at five of them: four in York County and one in northern Aroostook. We are still years away from actual control of EAB, but it is encouraging to start recovering parasitoids.
Image: Emerald ash borer biological control release sites from 2019-2025.
With the many new detections of EAB in Maine in recent years, we would like to establish new biological control release sites. The ash-dominated forests that serve as release sites can be public or privately owned. Many of our cooperators are private woodlot owners. Ideally, we would like to ship biological control directly to a local landowner or manager and have them conduct releases after training by MFS. The releases take 5-15 minutes, 4-6 times a summer for two summers. We are looking for new release sites in areas where EAB has recently become established. Specifically, we would like to find sites in or near Bar Harbor, Solon, Belfast, the Bath/Brunswick area, coastal Maine south of Portland, and western Maine west of Lewiston. If you have forested land in one of these areas and are potentially interested in having it become a biological release site, please review the guidelines and information about EAB biocontrol available on-line, and email [email protected] with the town in which your ash stand is, the approximate acreage of ash, and the coordinates (approximate is fine) of the stand. If it looks like your land would be suitable for a biological control site, we will reach out to you.
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Image: Areas of interest for establishing emerald ash borer biological control.
Ash Preservation Project – Year Two Update
The MFS expanded its Ash Preservation Project this year to protect more of Maine’s ash trees from the emerald ash borer (EAB). In 2025, a total of 108 ash trees were injected with systemic insecticide at nine new sites across the state, tripling the number of locations treated in 2024. These locations include a mix of private properties, town forests, state lands, land trust holdings, and college campuses.
The same product and application method used in the first year were applied again this season. Emamectin benzoate can provide protection for up to three years, so trees treated this year will be revisited in 2028 for their next round of injections. So far, landowners have reported encouraging results from the first year’s work, noting fuller canopies and improved tree health in treated ash.
Image: An ash tree at Gilsland Farm Audubon Center before and one year after insecticide treatment.
MFS’s growing network of treated ash trees is designed to act as a living refugium for Maine’s ash population. By maintaining healthy trees across different landscapes, the project aims to preserve an ash seed source, ash’s genetic diversity, cultural value, and environmental benefits while EAB continues to spread. Monitoring will continue and additional sites will be added as new partners are added.
Readers interested in pursuing treatment of their own ash trees by private applicators are encouraged to read more about insecticide treatment options. The ideal seasonal treatment window has passed; we encourage those near EAB infestations considering treatment to prepare for the coming spring, when treatments have been shown to be the most effective.
Spotted Lanternfly (Lycorma delicatula)
Typically, a handful of spotted lanternflies (SLF) are intercepted in Maine each year. You might even remember the news headline about SLF coming in on cruise ships visiting ports along the New England and Atlantic Canada coast from a few years ago. While 2024 happened to be a quiet year with no known reports or interceptions, SLF showed up in Maine again right around Labor Day weekend 2025. Sightings spanned the distance from Gray to Lewiston. One of the locations happens to be the parking lot of a rest area on I-95, the other a busy parking lot again within spitting distance of I-95, and a third was spotted outside of a warehouse receiving product from more southern states. Coincidence? While Maine does not have any known established populations of SLF, they are certainly doing well in southern New England, New York, and beyond. An undesirable creature to begin with, one of their challenging traits is the ability to hitchhike on motor vehicles and be carried great distances along transportation corridors. Many have had the experience of watching a live insect clinging to the glass windshield of a vehicle at highway speeds without falling off and wondering how on earth that can be possible. Regardless, it certainly is possible, so this is a reminder for neighbors visiting Maine and Mainers visiting our neighbors: check your vehicles before you hit the road and make sure you are not giving SLF a free lift into Maine. Keep your eyes peeled for this pest and its favorite plant, tree-of-heaven. Learn more on the CAPS spotted lanternfly website.
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Images: (Left) Adult spotted lanternfly observed in the parking area of a rest stop on I-95 in Gray, ME over Labor Day weekend; (Right) Adult spotted lanternfly observed in the parking lot of a business bordering I-95 in Gray, ME over Labor Day weekend.
Spruce Budworm (Choristoneura fumiferana)
MFS adopted a new approach to our spruce budworm pheromone trapping program in 2025 to help address some standing issues with the old program. Traps were removed earlier than usual this season to provide data to landowners sooner, except for three traps that remain to be collected this week due to a road closure. In total, 116 traps were operated in 2025, compared to the typical 350+. Call it a test run; we did this to try a new combination of lures and trap styles prior to considering another increase in the overall scale of the program. The University of Maine at Fort Kent is also performing a field study this season that takes an even closer look at what the best combinations of lure brand and trap style might be.
In previous seasons, many of the highest average moth counts came from sites in northwestern Aroostook County along the Quebec border. As many are aware, there was a large-scale treatment program in this area in 2025. As expected, these sites no longer represent the highest average moth captures in the state. Instead, and perhaps not surprisingly, the highest average moth captures have now shifted towards places like north central Aroostook County (areas surrounding Fort Kent) and northeastern Aroostook County along the New Brunswick border. Although preliminary data reveal these areas may now have higher trap captures than treated areas further west, it is important to note that overall moth captures are still down statewide. For example, the highest average moth capture anywhere in Maine in 2024 was 329.7, whereas the highest average moth capture anywhere in 2025 is just 153.5. The pheromone traps provide an early look at populations, and can sample moths that developed far from the trap site (as far as Ontario!). L2 sampling will help hone in on local populations and narrow down areas eligible for treatment in 2026.
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Images: (Left) Map of Maine Forest Service spruce budworm pheromone trap sites operated during the 2025 survey season; (Right) Contents of a spruce budworm pheromone trap showing moths captured in 2025.
The Maine Forest Service is seeking information from Maine landowners who may be interested in participating in an SBW EIS program in the future. The program would involve subsidized insecticide treatments of spruce-fir forestlands with building SBW populations. For those interested in this upcoming cost-share program, please fill out this interest form and stay tuned for details.
In late summer we typically receive numerous identification requests for caterpillars that people encounter as they are outdoors.
Gallium/Bedstraw Sphinx (Hyles gallii)
A common sight in late summer, particularly August, are large, fast-moving gallium sphinx moth caterpillars crossing the road. These caterpillars can be brown, black, or green, with whitish spots on the side of the body and a black or red horn towards the rear end. Larvae feed on bedstraw (Galium spp.), fireweed (Epilobium spp.), and other plants in the evening primrose family (Onagraceae). These caterpillars can be found in May through August and have a broad distribution in the northern U.S. and southern Canada.
Image: Brown color morph bedstraw sphinx caterpillar.
Isabella Tiger Moth (Pyrrharctia Isabella)
One of the most recognizable native caterpillars in North America has made its seasonal appearance in Maine. The Isabella tiger moth caterpillar is colloquially known as the “woolly bear”, and the number of rusty-brown colored segments is said to predict the intensity of the upcoming winter season. Woolly bears don’t feel very woolly – instead, they have bristled hairs on their body that can be irritating to sensitive individuals. Because woolly bear caterpillars are a native species, they are generally not a forest health concern, although they can defoliate birch, elm, and maple in addition to a variety of grasses. These caterpillars can often be seen on the roadways during Autumn. If you’ve ever wondered, “Why did the woolly bear caterpillar cross the road?” it’s because it's in search of a safe spot to overwinter as a pupa.
Image: An Isabella tiger moth, “woolly bear” caterpillar wandering on a host leaf in early September.
Red-lined Panopoda (Panopoda rufimargo)
Sometimes identification requests are prompted by leaf damage in the area where the caterpillars are found. A recent submission included the photo below of a red-lined panopoda caterpillar which is a widespread species occurring east of the Rockies from southern Canada down to the Gulf Coast. The larvae of this species uses members of the beech family as hosts including American beech, red oak and white oak. The adult moths are a greyish brown with two red lines that cross the fore and hind wings, giving this species its common name.
This genus is more diverse in tropical Central and South America, with only four species occurring north of Mexico. The larvae in this group have large suction cup-like prolegs, which are leg-like extensions of the exoskeleton towards the rear of the caterpillar that help it grip leaves and twigs. This genus belongs to the same family (Erebidae) as the dreaded browntail moth (Euproctis chrysorrhoea), although they belong to a different subfamily and lack irritating hairs.
Image: Lateral view of a red-lined panopoda caterpillar in Kennebunkport, ME.
Beech Leaf Disease (Litylenchus crenatae mccannii)
Image: Current distribution of beech leaf disease in Maine by year.
Beech leaf disease (BLD) has been confirmed in 381 towns in Maine, with 165 confirmations in 2025 (43% of all confirmations since 2021). Reports from the public and surveyors continue to be received with the newest reports coming from along the border of northern Penobscot and southern Aroostook County.
This time of year (late summer/fall) is thought to be the primary dispersal period for the nematode that causes BLD. In late summer, populations of BLD nematodes in beech leaves are at their highest (see image below). During rain events, BLD nematodes (mostly thought to be juvenile females) exit the leaf and swim in thin films of water in search of a bud where they will overwinter (water is critical to the BLD nematode’s ability to move). In between exiting the leaf and finding a bud the nematodes can be picked up in a gust of wind or water droplet (they are only 0.8 millimeters long, weighing 0.12 micrograms) and transported potentially long distances. There are also other likely modes of BLD nematode dispersal that have not been fully clarified or proven through scientific study.
Once nematodes become established in a bud, they begin to feed, altering plant cells and their functions. The type and severity of damage will be seen as symptoms when leaves emerge in spring – unless the bud is so severely damaged that it does not survive. Frustratingly, there is nothing that can be done to prevent the natural spread of BLD and focus should instead be on protecting trees with the few management tools available. Descriptions of current BLD management processes can be found on the Maine Forest Service BLD website where you can also find the latest information on BLD in Maine.
Image: (Left) A single BLD nematode under high magnification; (Right) A 2-mm section of beech leaf under magnification, orange arrow pointing to a plant cell wall; all the white, stringy masses throughout the cells in the image are thousands or BLD nematodes.
Late-Season Leaf Spots and Blotches
If the leaves of trees look a bit ragged at this time of year, that’s because they have made it through an entire growing season of biotic attacks from insects and disease and potentially adverse abiotic conditions (non-living conditions related to weather, mechanical damage). The good news is the leaves have made it this far and they have achieved a large proportion of the work (photosynthesis) they were intended to do. Thus, even unsightly late-season leaf spots and blotches are of minor concern. Thankfully, we can begin the process of minimizing leaf damage next year by our actions in the coming months. In addition to late-season leaf spots and blotches, many more damaging fungal leaf pathogens can be present on leaves this time of year that never expanded or spread due to host defenses or dry weather conditions. So, cleaning up and removing dead and shed plant material in fall is a good way to limit sources of infection for next year. This is of course not practical in forest settings. In such cases it is worth remembering that native fungal pathogens are an ever-present, natural part of Maine’s forest ecosystem that only represent a problem when host susceptibility and environmental conditions combine in such a way to cause disease.
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Images: (Left) Linden leaf blotch; (Right) giant tar spot of Norway maple are late-season leaf diseases that look serious aesthetically but typically harm trees very little.
Natural Fall Needle Drop
Conifers drop their oldest needles/leaves in fall in favor of prioritizing resources for growth, defense and maintenance to newer, more productive photosynthesizing leaves/needles. This is seen as yellowing of needles further back on the branch with green needles remaining closer to branch tips. This color change in conifers can be alarming, and the extent of this phenomenon can be related to summer growing conditions – a more stressful growing season may lead to earlier and heavier needle drop. Fall needle drop is not to be confused with similar symptoms of leaf/needle drop during the growing season that could be a sign of a serious tree health stressor like spruce needle casts, white pine needle damage, or blights or insect damage of white cedar. This serves as a good reminder to scout your trees and forest often and to know what is normal. When you see something that doesn’t seem right for a tree species, forest type or location, or time of year, do not hesitate to take pictures and report it via the Maine Forest Service Tree Ailment Form or by calling (207) 287-2431.
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Images: (Left to right) Seasonal needle drop in Maine in red pine, white pine, and white cedar.
While we are certainly sad to see her go, we are pleased to report our senior entomology technician out of the Old Town office, Zoe Albion, has decided to go back to school and was recently accepted into a graduate program at University of Maine – Orono. Zoe spent two productive years with Forest Health and Monitoring and was a huge help to our division during her time with us. For her graduate studies, Zoe will continue to work on forest health and her research project will focus on the collaborative emerald ash borer study currently underway with USDA-APHIS in Maine. She will be advised by Dr. John Daigle, head of the APCAW lab (Ash Protection Collaboration Across Waponahkik) that many of you may be familiar with already from our ongoing partnership with the APCAW group. Zoe, we wish you the best of luck, and are glad you are not far away!
“Elongate Hemlock Scale (Fiorinia externa) – Homeowners in Kennebunkport noticed the hemlocks they had planted about eight years ago were looking ragged. They initially attributed it to the excess moisture we’ve had this summer; however close inspection revealed strange things covering the undersides of the needles. A sample was submitted to Cooperative Extension, and the problem was subsequently determined to be elongate hemlock scale. It most likely was on the central tree in the planting when the trees were initially planted. Since the initial detection a second infestation has been reported on native and planted hemlock and balsam fir in Kennebunk.
These are the first records of established elongate hemlock scale in Maine and containment measures are underway for hosts within approximately 750 feet of the plantings. Primary hosts include hemlock and true firs (including balsam and Fraser); second tier hosts include spruces and other conifers, with the exception of pine. The detection of this insect in close proximity to hemlock woolly adelgid is troubling because the two together cause rapid decline of hemlock hosts. In addition, this pest can be a severe problem in Christmas tree plantations.”
September 19, 2025, 1:00 PM, Common Ground Fair, Unity, ME: Maine Forest Pest and Disease 2025 Update
Maine Woodland Owners hosts Brittany Schappach, an Entomologist with the Maine Forest Service to present Maine Forest Pest and Disease 2025 Update in the Low-Impact-Forestry Tent at the Common Ground Fair.
September 20, 2025, 10:00 AM - 11:00 AM, Common Ground Fair, Unity, ME: APCAW Presentation
Members of the APCAW lab and representatives from Maine Forest Service will present at the Common Ground fair in the Low-Impact Forestry Tent (Unity, ME).
September 24, 2025, 10:30 AM to 1:30 PM, Career Fest, Orono, ME
Join Maine Forest Service Entomologist Brittany Schappach at this year’s Career Fest hosted by the University of Maine in Orono. Career Fest is a career exploration and networking event designed to broaden students’ interest in a variety of career fields. This event will be held on the University Mall in Orono and feature food trucks, treats, and other outdoor activities. Email Eric McPherson with any questions at [email protected].
September 27, 2025, 10:00 AM - 4:00 PM, Preserving Ash, Protecting Traditions
Presented by Great Pond Mountain Conservation Trust and the Ash Protection Collaboration Across Waponahkik, this event is focused on learning effective strategies to preserve ash and its unique cultural and ecological value, featuring expert talks including from FHM Director Allison Kanoti, and live Wabanaki basketmaking demos.
Registration and more info at greatpondtrust.org
Presented in partnership with Downeast Audubon and Native Gardens of Blue Hill.
October 23, 2025, 1:30 PM, Corinna, ME: Jumping Worms in Maine
Hosted by the Sebasticook Garden Club, join Maine Forest Service Entomologist Brittany Schappach to learn more about invasive jumping worms (Amynthas spp.) in Maine. Topics include biology, how to distinguish jumping worms from other earthworms, forest impacts, and current management and prevention strategies. This free event will be held at the American Legion in Corinna. Email [email protected] with any questions.
Conditions Report No. 5, 2025
On-line
Department of Agriculture Conservation & Forestry, Maine Forest Service – Forest Health and Monitoring
Contributors: Aaron Bergdahl, Amy Emery, Gabe LeMay, Mike Parisio, Brittany Schappach, Colleen Teerling, and Andy Whitman.
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