Asian Giant Hornet (Vespa mandarinia) – Nothing sells news more than an exaggerated, scary story and that is certainly the case when it comes to “murder hornets.” These “murder hornets” are not invading the U.S., and the people that should be aware of these hornets are residents in Washington state and southern British Columbia to make sure it doesn’t get established. The murder aspect of the hornet refers to the way it goes after European honeybee larvae, which also happen to be non-native. Like all hornets and social wasps the Asian giant hornets have no interest in humans unless you are disturbing their nest/larvae. We can assure you that there is nothing to worry about as far as Asian giant hornets are concerned. With warmer weather comes increased insect activity and there are a couple of large wasps that are found in Maine that may be confused for the Asian giant hornet.

A related wasp in the same genus is the European Hornet (Vespa crabro) which has been established in the U.S. since the 1800’s. European hornets are very large wasps that look very similar to Asian giant hornets. They typically nest in dark cavities, usually hollow logs deep in the woods. People usually come into contact with this species in the spring when new queens are beginning to make nests or in the fall as workers change from capturing other insects to a scavenging lifestyle.

The other look-alike is the aptly named eastern cicada killer (Sphecius speciosus), which is one of our largest native wasps. These large non-aggressive wasps build nests in the soil, often in lawns, and are commonly encountered during the summer months. The females provision their nest with a cicada they capture and paralyze, in which they lay an egg and bury. The males can be territorial and may fly in a seemingly aggressive manner ‘buzzing’ intruders, but due to a lack of a stinger, they are incapable of stinging. Images: (left and middle) Side-by-side comparison of Asian giant hornet and the closely related European hornet. Getty; (right) Female cicada killer and prey. S. Larcolt.

Browntail Moth (Euproctis chrysorrhoea) – Although most of the world is still in quarantine, browntail moth caterpillars have ended their self-imposed winter quarantine and will be found basking on the outside of their winter webs and feeding on newly emerging leaves. This year we will be monitoring weekly caterpillar development and monitoring for outbreaks of the fungus that attacks BTM, called Entomophaga aulicae. The Maine Forest Service would like your help in reporting cases of diseased caterpillars so we can track the progression of the outbreak. Infected caterpillars will have a puffy, swollen appearance and are covered in whitish/yellowish dust, which are spores of the fungi. As caterpillars succumb to the fungus, they will hold tight to the branches they die on which helps the spread of the browntail caterpillar-killing spores. Reports of diseased caterpillars can be made at https://www.surveymonkey.com/r/9VKYFLV.

The new risk map for 2020 is along with winter web survey data can be found on the MFS website, follow the link for browntail moth from www.maineforestservice.org. Web abundance increased in Waldo, Knox and Hancock counties. Fewer webs than in previous years were observed heading south along the coast, but populations in many of those areas are still heavy enough to cause impacts to people.  MFS and Maine CDC will again be collaborate with 211 to answer the call volume associated with BTM. Be sure to check out the FAQ page which has a lot of great information on this itchy tree- and human health pest. Images: Dead Browntail moth caterpillars infected with E. aulicae; Browntail moth risk map 2020. MFS

Eastern Tent Caterpillar vs Browntail Moth (Malacosoma americanum; Euproctis chrysorrhoea) – It’s a case of mistaken identity. Every season we receive calls from concerned citizens who mistake eastern tent caterpillar nests for browntail nests. Two key differences between the typical nests these species make are size and position on the tree.

The silken nests of native eastern tent caterpillars start small but can grow quite large, reaching around the size of a football and are attached to the tree where the branches meet the trunk.  Eastern tent caterpillars lack the two orange spots on the tail end of the caterpillar. 

Browntail winter webs are the size of your palm or smaller and are constructed in late summer/early fall on the tips of the branches and are comprised of silk that also incorporates the leaves on the branch tips.  As the caterpillars become active in the spring, they travel in and out of the web, and the web can become surrounded in gauzy silk similar in texture to that made by eastern tent caterpillar. Browntail moth caterpillars are dark brown and have two orange spots towards the rear of their bodies. As the caterpillars molt, they develop white stripes due to white tufts of hair on each segment.

The photo shows an eastern tent caterpillar nest (upper) next to a browntail moth winter web (lower) (note, the eastern tent caterpillar nest is less dense and will continue to enlarge as it develops through the spring and summer). Image: BTM winter web next to Eastern tent caterpillar web. MFS

Winter moth (Operophtera brumata) – Last September an emergence cage was set out in Boothbay Harbor that contained 500 cocoons of the biocontrol for winter moth, Cyzenis albicans. Boothbay Harbor was selected as the release site for this very important fly due to the high population of winter moth which caused a great deal of defoliation there in the spring of 2019.  On April 29, we released the Cyzenis flies from their holding cage. This year we had great fly emergence and counted over 100 that came out early; the rest of the flies will emerge throughout May. After mating, the flies will feed on nectar from spring flowers, including maple trees. After the females fully mature, they will seek out leaves damaged by winter moth caterpillars and lay their eggs, which will then be ingested by the caterpillars. The fly eggs will hatch inside the wintermoth larvae, leading to mortality. Image: Forest entomologist Mike Parisio counts emerging Cyzenis albicans. MFS

Red Pine Scale (Matsucoccus matsumarae) - Since first detected in Maine on Mount Desert Island in 2014, red pine scale continues to spread slowly but surely. The last time we reported on red pine scale was in our October 2019 conditions report following a new detection in Kittery, ME. Since then, new locations with red pine scale populations have been identified both on Hancock Point and in Gouldsboro, in addition to being highly-suspected on the nearby Sorrento peninsula.

Our current knowledge of the whereabouts of red pine scale in Maine remains limited, but what we do know so far supports wind driven dispersal in a favorable coastal microclimate. Our ability to detect this pest efficiently remains hampered by its cryptic nature and masking of symptoms by other prevalent red pine issues, primarily shoot blights that cause similar discoloration of foliage. We will continue to survey for red pine scale simultaneously in conjunction with current red pine pathogen monitoring activities, in addition to survey work around the core known areas and further down east into Washington Co.

This insect is incredibly hard to see and usually cannot be confirmed without the aid of a microscope. However, in a time where we’re all doing more yard work than we’d usually have time for, you might be lucky enough to glimpse the white wool-like covering produced by the insect on the twigs of red pines. If you do happen to see anything resembling the photo below while pruning or raking this spring, please contact the MFS Insect & Disease lab. Image: Small amounts of white flocculation produced on the twigs of red pines harboring red pine scale populations. Karen Coluzzi, Maine DACF.

Algae and lichen growing on trees – Trees provide a habitat for a variety or organisms, including lichens and even algae. The insect and disease lab received several requests for assistance in past months directed at the organisms pictured here: The reddish filamentous algae, Trentepohlia spp., and the sunburst lichen, Xanthoria elegans. Although these brightly colored colonizers of trees look alarming, neither of these organisms pose a health risk to trees. In fact, lichens are very sensitive to air pollution and their presence indicates good air quality. Image: Trentepohlia spp. exist on many tree species but are often noticed on trees with lighter colored bark, like this birch also hosting a few species of lichen; a tree heavily colonized with sunburst lichen in Thomaston Maine. MFS

Red Pine Survey Preliminary Results – In response to questions by industry and the general public about the health of red pine, a survey of planted red pine stands was initiated in 2019, with 22 sites and roughly 550 trees evaluated. Diplodia tip blight was recorded at all but one site, while Sirococcus shoot blight was present at 7 of 22 sites.  Each time Sirococcus was found on site, Diplodia was also found and together they represented serious negative impacts to stand health. Heavy infection levels were observed in red pine plantings in Androscoggin, Aroostook, Cumberland, Kennebec, Lincoln, Oxford, Penobscot, Sagadahoc, Somerset, and York counties. The survey is planned to continue in 2020 to better understand the distribution and severity of disease impacting red pine resources. Image: Small and thin red pine crowns in a dieases-impacted stand viewed from the ground. MFS.