Forest & Shade Tree – Insect & Disease Conditions for Maine
July 31, 2024
“Pink striped oakworm- This insect became quite abundant last year along a hardwood ridge in the Passadumkeag area. The larvae are heavily patterned in a variety of stripes and spots and have pinkish stripes on their back and sides and a series of paired spines on their back. Reports of moth activity in eastern Maine along the Machias River indicate an infestation there. Food plants in addition to oak are varied and they were collected last year from many trees including poplar, maple, and birch.”
The June 2024 conditions report featured some dramatic photos of forest tent caterpillar defoliation in northern Aroostook County extending from Maine to neighboring New Brunswick across the Saint John River. Several weeks later, reports from our senior entomology technician up north indicate that the aspen is recovering quite well. Shortly after we flew over these areas, we received some tips about forest tent caterpillar activity in the Saint Pamphile area, as well as some adjacent areas across the border in Quebec. Unlike the areas in northern Aroostook County, where caterpillars fed almost exclusively on aspen, here the sugar maples in the area’s numerous sugar bushes that were under attack. As you can see in the included photos, visible damage was isolated to these maple sugar dominated stands and appeared as islands of discoloration amidst the otherwise healthy surrounding canopy. These areas will require follow-up to see how they are recovering, but this level of defoliation could affect next year’s sap production, and it may be wise for these maple syrup producers to give these trees a rest before tapping them at full capacity again.
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Image: Sugar maples defoliated by forest tent caterpillars along the Quebec border in Aroostook County, ME.
Keeping with the theme of sharing a forest boundary with Quebec and therefore sharing forest health issues along the border, spruce budworm (SBW) defoliation has also crossed into Maine in northern Aroostook County. As reported in the June 2024 conditions report, we were aware of heightened SBW activity in this area from the results of Maine’s pheromone trap network, overwintering larval (L2) surveys, as well as defoliation data from satellite imagery analysis in Quebec. Since we were unable to conduct aerial survey of these areas in 2023 due to inclement weather and wildfire smoke, we can’t comment on how these stands appeared from the air prior to 2024.
In addition to survey data, several ground reports from land owners and managers and field staff cued us into some specific damage areas, and we easily located the affected areas along the Quebec border using this information. Several blocks of forest in the same general area were treated by the landowner in accordance with the Early Intervention Strategy currently being implemented in Atlantic Canada. Without early intervention strategy insecticide treatments conducted in June, we expect the visible damage area would have been more extensive.
By survey time in mid-July, feeding damage from SBW larvae was completed, and partially eaten needles had time to become visibly reddened or brownish. Just under 3,000 acres of damage were mapped. The pilot was able to land in one location for the survey crew to assess the condition on the ground. They found that defoliation was lighter than expected based on first impressions from above the canopy, with feeding limited to current-year needles. There was little or no evidence of defoliation on needles from previous seasons, indicating a quick growth of the population in this location.
MFS plans additional ground surveys this season and more details will be shared in future reports.
Image: Discolored spruce-fir forest due to spruce budworm larval feeding in northern Aroostook County, ME. Note the Canadian border running through the center of the photo showing contiguous damage spanning into Quebec.
Image: Despite the severity of discoloration visible on fir from the air, when viewed from the ground at this location defoliation was less severe than anticipated and generally confined to current-year needles.
The Maine Climate Council wants to hear from you!
The Maine Climate Council seeks community feedback on the draft recommendations presented by the Working Groups for the update to the Maine Climate Plan through an online survey. To make it easier for respondents, the survey is divided into sections, allowing users to provide their full feedback on all strategies or just preferred key areas. Each smaller survey takes an average of five minutes or less to complete. The full survey is expected to take around 20 minutes.
Please consider reviewing the draft climate strategies and submitting your feedback.
Climate Update July 2024
Image: The average difference in temperature in June 2024 compared to average normal temperatures from 1991-2020 (left). Overall, the month of June 2024 was warmer than normal, with most of the state seeing a 3-5°F average increase in temperature. The percentage of normal precipitation compared to the normal precipitation from 1991-2020 (right). Overall, the month of June 2024 had near average rainfall for most the state. Source: Northeast Regional Climate Center.
Globally, June 2024 was Earth’s warmest June since 1850 (NOAA’s National Centers for Environmental Information, NCEI), and the fourth warmest June for Maine since 1895. Throughout Maine, June 2024 was significantly warmer than normal compared to recorded average temperatures from 1991-2020. Statewide temperatures averaged 64°F during the month of June, an average of 4.2°F higher temperatures than normal. Most areas of the state experienced an average temperature of 3°F to 5°F higher than normal, whereas some areas of the state only experienced slightly higher (1°F to 3°F) temperatures than normal. The town of Caribou had the hottest June on record with an average monthly temperature of 65.1°F, beating out the previous record of 64.9°F set in 2021. The three-month forecast projects temperatures to stay above normal through September.
Most of Maine experienced close to normal averages of rainfall in June with an average of 4.39 inches, with some northern parts of the state experiencing up to 200% more rainfall than normal averages and scattered areas experiencing less than 75% of normal rainfall. Statewide, the rainfall in June averaged 0.64 inches higher than normal averages according to data from NOAA. Last June, the state had one of the rainiest seasons on record, with an average of 6.43 inches of rain statewide. Above average rainfall is predicted through September.
Image: As of July 2nd, 2024, about 4% of the state is experiencing abnormally dry conditions. Sources: NDMC, NOAA, and USDA.
While much of the eastern U.S. is facing flash drought conditions, most of Maine had normal conditions during the month of June, with small areas in northern Piscataquis and Somerset counties and extreme southern York County experiencing abnormally dry conditions. In May, northern Maine had areas of moderate drought conditions, but due to above average rainfall in June, those areas are no longer experiencing any drought according to data from NOAA. The drought conditions in June 2024 are relatively similar to the drought conditions from this time last year, with 0% of the state experiencing any drought conditions. Normal soil moisture conditions are projected to persist throughout the summer (NOAA Climate Prediction Center).
Hurricane season in the Atlantic started on June 1; experts are predicting a greater risk for tropical cyclones and Category 3 or greater hurricanes for New England. There is about a 70% chance of La Nina conditions developing between August and October, which could create a more active hurricane season compared to normal. Last year, the most frequently predicted county to receive hurricane landfall in the U.S. was Maine’s Washington County. Although most of these hurricanes were “no-shows”, with their centers making landfall in Canada, Washington County did experience extensive wind damage from two storms last year.
Asian Longhorned Beetle (Anoplophora glabripennis)
The Asian longhorned beetle (ALB) is an invasive species that is NOT currently established in Maine. ALB is known to occur in Massachusetts, Southern New York, Ohio, and South Carolina based on surveillance from the USDA ALB Program. ALB can be introduced to new areas through the movement of firewood, so please leave your firewood at home and encourage those planning to visit Maine to do the same. To highlight the importance of community involvement in looking out for ALB, August is highlighted by USDA APHIS and cooperators as Tree-Check Month.
ALB larvae are grub-like and develop inside healthy hardwood trees; preferred hosts include maple, birch, horse-chestnut, popular, willow, elm, and ash trees. While inside, the larvae first feed just beneath the bark and create tunnels, which disrupts the tree’s ability to use water properly. This type of feeding can lead to dieback of the tree crown and eventually, death of the tree. More mature beetles feed deeper inside the tree causing structural damage. When adult beetles emerge in the late spring, they leave behind pencil-diameter holes in the bark of tree trunks and branches. The easiest time to find ALB is during their adult beetle life stage, predicted to start in July and last through October in this region.
In 2023 and to-date in 2024, we received several reports of ALB from the public, but upon further investigation, the reported beetles turned out to be native longhorned beetles. Most commonly, the white-spotted sawyer beetle (Monochamus scutellatus) is mistaken for ALB because of its similar large size and speckled appearance. White-spotted sawyer beetles are a common native woodboring insect that often attack weakened, dead, and dying trees and are not a significant threat to forest health.
Image: ALB are an invasive species that are glossy black, with antennae longer than their body and white spots on their elytra (wing covers) (left). White-spotted sawyer beetles are a bronze-black native beetle with antennae as long as their body and white spots on their elytra (right). White-spotted sawyers have a distinct white patch between their wing covers, whereas ALBs do not. Photos: Sarah Smith, USDA APHIS PPQ, bugwood.org.
Although both ALBs and white-spotted sawyers are black with white spots on their back, ALBs are glossy black, whereas white-spotted sawyers have a duller, bronze-black color. Importantly, white-spotted sawyers also have a white patch between their wing covers (right behind their “neck”), whereas ALBs do not. If you’re not sure which beetle you’re seeing, please send us a report (with photos!).
Browntail moth (Euproctis chrysorrhoea)
While most emergence happened earlier in the month, adult browntail moths are still active in late July. However, mass emergences did happen earlier in the month. It is therefore still a good idea to keep any unnecessary outdoor lights off now through the early part of August to make sure you aren’t attracting more moths to your yard. Many of the female moths have already mated and laid eggs on host foliage. These egg masses are covered in hairlike structures exuded from the abdomen as the eggs are laid. This covering prevents the eggs from drying out and serves as a barrier to would be predators, however they are not the same irritating hairs that the caterpillars possess.
Image: A female browntail moth laying eggs on host foliage, Turner, ME.
Elm sawfly (Cimbex americana)
This hefty elm sawfly larva was recently spotted on a street tree in midcoast Maine. Cimbex americana is a large insect native to North America whose larvae are identified by their pale coloration, black dorsal stripe, and black spiracles along the side of the abdomen. Though similar in appearance to caterpillars, sawfly larvae can be distinguished by six or more pairs of prolegs, compared to just two to five pairs on true caterpillars.
Image: Elm sawfly larvae will feed on the foliage of elms, willows, birch, boxelder, dogwood, and many other tree species.
In Maine, the 1-inch-long adult elm sawflies are common in alder thickets on warm sunny days in May-June. Despite loosely resembling hornets, they cannot sting (though they can bite). Eggs are laid on leaves via the female’s saw-like ovipositor and the larvae appear soon thereafter in July to feed on the foliage of their preferred hosts, elms and willows, as well as others including birch, boxelder, and dogwood. They’ll continue to feed until their maturity, at which they can reach nearly 2.5 inches in length! While their feeding can lead to some noticeable defoliation, control is not normally necessary or recommended.
Elm zigzag sawfly (Aproceros leucopoda)
Not to be confused with our native elm sawfly described above, the invasive elm zigzag sawfly isn’t known to occur in Maine but has now been reported from a number of eastern states, including New York, Vermont, Massachusetts, and the provinces of Quebec and New Brunswick. The larvae of this species are smaller, pale green, and create an unmistakable zigzag feeding pattern on elm leaves. Defoliation can become quite severe as the larvae grow and begin to devour whole leaves, in some cases affecting the entire crown of a tree once a population is large enough. While mortality hasn’t yet been observed in the U.S., defoliation can predispose elms to diseases and other stressors, so please report any sightings of this distinctive damage if observed on elms.
Image: Elm zigzag sawfly damage outside of Albany, NY.
Forest Tent Caterpillar (Malacosoma disstria)
Now that the wave of forest tent caterpillar feeding has concluded in the north, it is worth reflecting on the scale and range of the feeding which occurred. As of the latest aerial survey earlier this month, the defoliated area mapped totals 60,503 acres of damage. The vast majority of this occurred in the northeast portion of Aroostook County, between Presque Isle, Fort Kent, and Van Buren. Aspens were the most often affected tree species, and fortunately refoliation has now been observed across the affected area.
There have been some notable outliers, however. On the western border of the state in T7 R19 WELS, MFS staff observed forest tent caterpillar defoliation on sugar maples and yellow birches in addition to aspens. Overstory maples appeared to be up to 50% defoliated at the time, prompting concern from local sugarbush operators. Private forest management companies reported similar damage in the area, which appears to be related to a larger forest tent caterpillar outbreak occurring just across the border in St. Aurelie, QC. Whether this outbreak will further spread into Maine in the following seasons remains to be seen, but MFS will continue to monitor this area due to potential impacts on the maple products industry.
Image: In addition to the large aspen defoliation observed in northeast Aroostook County, forest tent caterpillar damage also occurred on maples and birches in western Maine.
Snipe Flies (Rhagio spp.)
Snipe flies are a common sight in the woods during the summer, particularly in wet areas with abundant understory vegetation. They get their name from their mouthparts which resemble the beak of a shorebird called a snipe. They are also sometimes called down-looker flies from their habit of resting on vegetation and tree trunks while facing the ground. This genus of snipe flies is the namesake of the family to which these flies belong, Rhagionidae, which contains 25 species in North America and 160 species worldwide. The species most common in Maine are sit-and-wait ambush predators that feed on other insects. Snipe fly larvae live in moist soil and leaf litter and are predators of other invertebrates.
There is a pathogenic fungus called Furia ithacensis, that is only found on flies in this family. Once infected, the fungus causes the flies to die clinging to the undersides of leaves, sometimes in large numbers. Specialized hyphae called rhizoids erupt from the flies and grab ahold of the leaf, as seen in the image below. It is thought that the leaf acts as an umbrella preventing the fungal spores from being washed away in the rain. Spore producing structures erupt from the softer membranes of the fly and discharge a circular halo-like pattern of spores.
Image: Snipe flies killed by Furia Ithacensis on the underside of a beech leaf.
Urocerus albicornis
While performing a survey in Auburn, field staff stumbled upon a species of primitive wasp belonging to a group of non-stinging wasps called horntails. The specimen was collected and identified as a male Urocerus albicornis, which has no common name. This species is native to North America and inhabits the southern boreal forest in Canada down to the southern United States. This species prefers dead and dying conifers, including fir, spruce, pine, hemlock, western redcedar, larch and Douglas fir. The females of this species are larger and have dark bodies with white cheeks, black and white striped legs as well as an egg-laying organ called an ovipositor on the underside of the body. Both males and females have a short projection on their abdomen which gives the group the common name of horntail. Larvae develop from eggs laid inside dead and dying trees and require a symbiotic fungus to digest the cellulose component of wood. Males emerge before the more abundant females to disperse and prevent inbreeding. Adults can be found flying on sunny days in areas where host species are abundant.
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Image: Male Urocerus albicornis under magnification, collected in Auburn, Maine.
Ash Rust (Puccinia sparganioides)
Recent reports of a severe disorder affecting many ash trees in Thomaston (Knox County) prompted a visit by MFS staff on July 25. Trees were described as wilting, appearing scorched and dropping their leaves. Upon entering the impacted area, which encompasses a large proportion of the town, the disorder impacting the trees was clear: a severe outbreak of ash rust.
Ash rust, like most rust fungi, requires two hosts to complete its life cycle: any of Maine’s three native ash species (Fraxinus americana, F. pennsylvanica, F. nigra) and grasses commonly found in coastal areas (genera Spartina and Distichlis). The fungus alternates between hosts, with the fungus producing spores on ash trees in summer that infect the marsh grasses, and the fungus on the marsh grasses in turn producing spores infecting newly emerging ash leaves in spring. Symptoms typically begin to appear mid-June as small yellow-orange spots on upper leaf surfaces. Bright orange clusters of fungal spore-producing structures (aecia) develop within two weeks and become apparent on leaf petioles and leaf undersurfaces, causing swelling and girdling of leaf petioles and necrotic (dead) areas of leaf tissues that expand over time. Affected leaves may wilt causing severely infected trees to appear scorched and leaves are shed from trees. Vigorous trees may flush new growth that will have smaller, lighter green leaves, causing crowns to appear thin and sickly. Severe infections occasionally result in the mortality of ash trees on poor sites or those already impacted by other disorders.
As with any tree stressor, impacted trees can become susceptible to secondary agents of decline. Fertilizing impacted trees in fall may replenish resources lost to defoliation. Chemical management of ash rust is seldom warranted but may be attempted on high-value trees. Applications of fungicides containing myclobutanil starting at bud break and repeated at two weeks and four weeks post-bud break may provide some control, but this approach has not been thoroughly tested under Maine conditions.
Whether ash rust will be a problem in the Thomaston area next year is unclear. Ash rust outbreaks of this magnitude are infrequent because an optimal combination of moisture, temperature and weather conditions are required for spore dispersal on both hosts at the two different times of year when this occurs. In the most recent outbreak in Columbia Falls (Washington County) in 2022, the disease was found at much lower levels in 2023, but reemerged causing damage in a significantly smaller area in 2024.
Images: (left) A road in Thomaston lines with defoliated ash leaves and roadside ash trees with wilting and scorch-like symptoms; (right) The general surveyed area containing ash tree impacted by ash rust.
Image: A close-up of ash rust pustules on leaf petioles (orange arrows) and on the upper and lower side of leaves (green arrows).
Beech Leaf Disease (Litylenchus crenatae mccannii)
Beech leaf disease (BLD) is consistently being found in new areas of Maine and is currently found in 15 of 16 of the state’s counties, with over 72 new town reports in 2024, and a total of over 169 towns since the disease was found in 2021. BLD is spreading at a very rapid rate in Maine and in other states where it is found.
One common misconception about BLD is that the symptoms seen on beech progress over the course of the summer. This is not true because the damage seen in the leaves visible in summer is a result of the causal nematode’s activities as it overwinters in beech buds. While the banding and thickening/crinkling symptoms of leaves tend to be more easily discerned as leaves expand and tissues mature, the number of bands does not increase and the general symptoms expressed in the leaf like thickening and leathery characteristics do not develop or progress.
On a slightly positive note regarding BLD, there is a new tool available for treatment of the disease that was recently approved by the Maine Board of Pesticides Control and the US Environmental Protection Agency via a Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) Section 24(c) Special Local Need Label. The product is the fungicide Arbotect 20-S containing the active ingredient Thiabenzadole. This product has been used for the prevention of Dutch elm disease in elms and to prevent sycamore anthracnose. How Thiabenzadole prevents BLD symptoms is not certain, but it seems to work very well when applied correctly via macroinjection, purportedly providing two years of protection. As described above, a summer application of Arbotect 20-S will not cure symptoms seen this year, but it will prevent symptom development for the following two years.
Image: A 17-inch DBH beech tree being injected with Arbotect mixed with approximately 5 gallons of water.
Image: Clear symptoms of BLD in the stand where the tree picture in the left image is growing.
The other tool used to support tree defenses against BLD is the soil drench fertilizer product Polyphosphite 30. How this product works to manage BLD in beech trees is also not fully understood, but it has shown good results in cooperative trials by Bartlett Tree Research Labs and Cleveland Metroparks in Ohio that started in 2015. Last year, the Maine Forest Service began the same kind of cooperative trial partnering with Viles Arboretum in Augusta and MFS Urban and Community Forestry in an area recently impacted by BLD. Polyphosphite 30 soil drench requires two applications: one in June and the second in July, about a month apart. The first and second applications occurred in June and July, respectively, in 2023 and the 2024 June application was recently administered, with the second application scheduled for late July.
A Call for ‘Clean Beech’: Do You Have Trees Resistant to Beech Bark Disease?
The Maine Forest Service would like to talk to public or private landowners who have beech trees that show a high degree of resistance to beech bark disease (BBD), a disease which has plagued beech trees in Maine for decades. Protecting these so-called ‘clean beech’ via Arbotect 20-S injection (See the article on beech leaf disease in this Conditions Report) would preserve BBD-resistant genetics and beech tree genetics in general. The MFS would like to select several sites with the following selection criteria: Larger beech trees (preferably over 15-inch DBH) with BBD-resistant characteristics (smooth bark, absence of cankers, absence of beech scale insects); sites with ease of access due to the need to transport larger volumes of water needed for the macroinjection process; forested sites where site disturbance and/or harvesting are not planned for the foreseeable future. This project has a similar design and aims as the emerald ash borer-related ash preservation project also underway by MFS and cooperators. If you have clean beech that meet the abovementioned criteria, contact the MFS at (207) 287-2431.
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Image: A beautiful, straight beech showing a high degree of resistance to beech bark disease, an excellent candidate for preservation.
Image: A close-up of the bole of a beech bark disease-resistant beech.
Finally, recent updates have been made to the Beech Leaf Disease FAQ on the Maine Forest Service website. These cover commonly asked questions communicated to us via the hundreds of BLD reports that MFS has received so far this year such as: The trees in my yard/woodlot are infested with BLD, should I cut them down? If I cut down trees infested with BLD, what should I do with the leaves, branches and wood? Answers to these questions and more can be found on the website.
White Pine Needle Damage
Impacts of the white pine needle damage complex (WPND) were mapped throughout the eastern white pine resource in Maine during Maine Forest Service aerial survey flights in June. In fact, the damage was so common and prevalent that aerial surveyors were not sure how to map it since seemingly every white pine stand they flew over showed symptoms of WPND. The WPND complex consists of at least four different native pine needle pathogens with quite similar life cycles and symptoms. Now that most of the discolored needles associated with the disease have been shed and the current-year needles have continued to emerge and elongate, trees are again looking green instead of orange. This has been a great relief to many, and some have even reached out to the MFS to enthusiastically report this return to greenness. However, despite the recent improved aesthetics, it should be remembered that conditions for disease development occurring this year in late May and June will dictate disease severity within this same timeframe next year – this is the nature of the lifecycles of the fungi that cause WPND. Judging by the large amount of infected orange needles that have fallen this year, heavy WPND symptoms are expected next year. This is because as the infected needles were discoloring and dropping, the WPND fungi within them were releasing numerous spores during wet weather. These spores have already infected the newly emerging needles of this year’s growth. These needles will remain green until next late May or early June when they will discolor, produce spores for infection and drop, thus repeating the WPND life cycle.
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Image: Roadside white pine trees pictured in late June still showing discoloration. These trees no longer appear orange after dropping their WPND-infected needles.
Image: A close-up of white pine branches showing WPND-infected needles and the green tips of expanding new growth.
Dutch elm disease (Ophiostoma ulmi, O. novo-ulmi)
Dutch elm disease (DED) symptoms have been noticeable since mid-June but have become increasingly apparent in July where elms grow in Maine – which is a lot more places than people generally realize. American elm continues to be found throughout Maine in road and field edges, in farm and forests settings, and some large elms still persist in urban areas and elsewhere. DED symptoms include yellowing of foliage followed by wilting and defoliation of leaves on infected branches. This is typically followed by reddening and drying of foliage and symptom progression from the point of infection toward interior portions of the tree. While pruning out infected limbs can be attempted, this rarely stops the disease from killing the tree. Mortality typically happens within three years of initial infection – although trees can die the same year they are infected. DED is present throughout Maine and infection centers seem to show up in areas, kill local elms and then the disease and its beetle vectors move on to new areas. There are two different elm bark beetle species known to transmit DED in Maine (Scolytus multistriatus and Hylurgopinus rufipes). A third, S. schevyrewi, has been found in many states including Connecticut, New York, New Jersey and Pennsylvania, but has not yet been found in Maine.
Current management recommendations include immediate removal of the infected tree, with the wood either debarked, burned, or buried to prevent insects from using the wood as breeding material. It is in this wood that elm bark beetles mate, mature, overwinter and are exposed to the spores of the DED fungus (spore-producing structures of the Ophiostoma spp. form in the beetles’ tunnels). When the beetles emerge in spring, covered with spores of the fungus that causes DED, they feed on the branches of healthy elm trees, transmitting the disease. Unfortunately, the best efforts of homeowners and municipalities to stop the spread of DED are often minimally effective. The best way to preserve elm trees is to have them treated with a fungicide injection to prevent DED infection. These injections offer multiple years of protection, but they are expensive and only practical for high-value elm trees.
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Image: Orange arrows showing points of Dutch elm disease infection, vectored by elm bark beetles, and associated symptoms. This tree died the following year.
Lesser Celandine (Ficaria verna)
The Maine Natural Areas Program (MNAP) is asking the public to keep a look out for invasive lesser celandine (Ficaria verna), also known as fig-root buttercup or Ranunculus ficaria. This plant has recently been spotted in several locations throughout southern and central Maine and can become a threat to Maine’s forest ecosystems. It is considered very invasive and challenging to manage once established. Lesser celandine has become most problematic in floodplain forests of other northeastern states.
Image: An example of Lesser celandine during flower.
Image: Lesser celandine taking over a floodplain forest in the United States.
Lesser celandine is native to Europe, Asia, and northern Africa, and came to the U.S. as an ornamental plant. It is perennial and low-growing, capable of forming large mats on the forest floor that prevent other plants from growing. Small bulbils may be present above ground later in the season and are easily spread by flowing water. The yellow flowers are in bloom from April-May, and by summer the plant dies back and becomes dormant. This creates areas of exposed bare ground, which leads to soil erosion and further spreads lesser celandine’s bulbils and tubers. These bare areas left in early summer are also colonized more easily by other invasive plants. Lesser celandine has been found invading riparian areas and then spreading to upland habitats where it continues to threaten native plant diversity, especially other flowering spring ephemerals.
Images: Lesser celandine’s unique tuberous roots and aboveground bulbils, which are the primary source of reproduction.
The leaves of lesser celandine are kidney-shaped and roundly toothed. Roots are tuberous and may break off in the soil, further spreading the plant. It is important to accurately identify lesser celandine from its native lookalike marsh marigold (Caltha palustris). Marsh marigold flowers have 6 petals while lesser celandine have 8-11 petals. Marsh marigolds also have larger leaves and do not have tuberous roots. If you believe you have found lesser celandine, or you would like to learn more, please contact invasives.mnap@maine.gov with the location and photos of your sighting. It’s encouraged to submit your sightings to iMapinvasives to further our understanding of where it has spread. If lesser celandine is manually removed, it is important to ensure all bulbils and tubers are also removed from the soil. Please visit the Maine Natural Areas Program’s website under the Invasive Species tab to learn more about other invasive species in Maine.
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Images: (left) The yellow flowers of Lesser celandine that bloom from April-May, usually with 8-11 petals; (center) 3 sepals attached to a long stem; (right) a leaf of lesser celandine.
August 6, 2024, Maine Public Radio: The Maine Calling episode on Maine Public Radio will focus discussion on beneficial insects; live at 11 am, rebroadcast at 7 pm and available on-line.
October 8-9, 2024, Wells Conference Center, Orono, ME and Virtually: The Future of Brown Ash: Weaving Indigenous Knowledge and Western Science to promote resilience amidst Emerald Ash Borer Invasion
A two-day gathering at University of Maine, Orono, will take place to inform people about current research about brown ash forests and reconvene the community of people who care for brown ash. We will have discussions, talks, meals, and posters. This meeting is hosted by APCAW.
Register or More Information
August 26, 2024 10:30AM-Noon, Virtual meeting: Emerald Ash Borer and Other Tree Health Concerns: DACF Update for Cities and Towns
Our next periodic update for municipalities will happen in late August or early September over Microsoft Teams. Oak wilt disease will be the focus. Rob Cole, oak wilt lead in New York State, will be our guest. We will also cover updates on other issues with the emerald ash borer in Maine.
Conditions Report No. 3, 2024
On-line
Department of Agriculture Conservation & Forestry, Maine Forest Service – Forest Health and Monitoring
Contributors: Aaron Bergdahl, Amy Emery, Chad Hammer (with intern Karen Karter), Gabe LeMay, Mike Parisio, Brittany Schappach, Thomas Schmeelk, and Andy Whitman
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