Browntail Moth (Euproctis chrysorrhoea) – 

Beware! 

Browntail moth caterpillars are feeding voraciously in coastal Maine and inland. The infestation is centered in the Bath/Brunswick (Sagadahoc/Cumberland Counties) but infested trees can be found from Kittery (York County) to Warren (Knox County) and inland to Turner (Androscoggin County) and Waterville (Kennebec County). The caterpillars are already stripping the trees of leaves in heavily infested areas and crawling across lawns, houses and cars to get to more food.

Photo: Browntail Moth (Euproctis chrysorrhoea) Note two orange spots on rear end. (Maine Forest Service)

The hairs from this caterpillar can cause a rash or respiratory distress in sensitive individuals. The hairs break off from the skins shed by the caterpillars. The hairs then blow in the wind or are stirred up by mowing, weedwacking, raking etc. Use caution when working outdoors in infested areas. 

Canadian Pine Scale (Matsucoccus macrocicatrices) – Samples of eastern white pine collected in T4 R11 WELS and T5 R11 WELS (Piscataquis County) for examination of pine leaf adelgid damage (see entry below) were found to also have what appear to be the overwintering cysts of Canadian pine scale.  Scales were found most commonly at branch nodes, but were also found on internodes.  One emerged adult was found on the samples.  This insect is generally thought to be of little significance from a tree-health perspective; although work is currently being done to understand more about its role in white pine dieback in southern states (for a recent MS thesis on the topic see:  https://getd.libs.uga.edu/pdfs/schulz_ashley_n_201508_ms.pdf).

Photo: Overwintering cyst (left) and emerged adult (right) believed to be species Matsucoccus macrocicatrices on eastern white pine.  (Maine Forest Service)

Eastern Tent Caterpillar (Malacosoma americana) – The webs of eastern tent caterpillar are quite abundant this year, with many cherries and apples supporting numerous webs.  These webs usually originate in branch junctions.  They’ll be full of the frass of well-fed caterpillars and often the caterpillars themselves. If the webs are an aesthetic problem, the best way to manage them is to wind them around a forked stick in the cool hours of the morning or evening, thereby ensnaring the occupants.  You can relocate the webs to another host tree out of sight (they do feed generalist predators and other beneficial insects), soak them in a bucket of soapy water or dispose of them in a sealed plastic bag.  Be cautious in browntail territory not to confuse the webs of the two species and also because you will sometimes find browntail moth caterpillars snuggled in with their cousins in the safe haven of the eastern tent webs.  

Photo: Eastern tent caterpillar webs are often found in cherry and apple trees.  (Maine Forest Service)

This time of year the native six-spotted tiger beetle adult has made its first appearance across the state. These blocky, long-legged, metallic green beetles are often mistaken for EAB. Adult EAB have not emerged yet in this region. EAB adults emerge at 550 GDD or when the black locust bloom.  The Northeast Regional Climate Center includes Concord, NH on their webpage Growing Degree Day Accumulations to support the tracking of emerald ash borer emergence.  

Photo: The native, beneficial six-spotted tiger beetle, Cicindela sexguttata.  (Wikimedia commons)

Forest Tent Caterpillar (Malacosoma disstria) – Although a close relative of the eastern tent caterpillar the forest tent caterpillar does not make tents. It feeds on the buds and leaves of oak, poplar, maple, birch and other hardwoods in the spring. The number of moths in light traps were up from the usual level from South Berwick (York County) and Hope (Knox County) to Crystal (Aroostook County) and Topsfield (Washington County). Maine has not had an outbreak of forest tent in decades so this is one to watch. Caterpillars feed on the leaves and then mass together on the trunks of trees when they mature and are starting to look for places to pupate.

Photo: Forest Tent Caterpillar, Malacosoma disstria, on a maple leaf (Maine Forest Service)

Pine Leaf Adelgid (Adelges pinifoliae) – Pine leaf adelgid damage visible during aerial survey was mapped on over 262, 000 acres in Piscataquis County last year.  Less severe damage extended beyond the area mapped.  2015 shoot growth was scant and significantly reduced compared to 2014 growth on samples collected in the Telos area this week. 2014 growth seemed to be most heavily colonized by the nymphs, which would indicate we should expect cone-like galls on current-year spruce growth (red and black) this year.  This is counter to what is in the literature, which reports galls in odd numbered years, so will be interesting to monitor.  Maine Forest Service Forest Inventory crews will help monitor the progression of this pest in the North Maine Woods this year during the course of their regular work in the area.  Others working in the affected area are encouraged to send reports of damage either to spruce or pine.  Bear in mind, samples may be needed to identify the causal agent.

Photo: Abnormally swollen shoots on spruce caused by pine leaf adelgid would be visible as the buds expand.  When the galls mature they resemble pine cones.  Unlike some other adelgid galls on spruce, these are not persistent on the branches, and most drop within the year they are formed. (W. Cranshaw, CSU, bugwood.org)

White Pine Needle Diseases – One-year-old needles of white pines infected with any one of the several needle diseases prevalent during the past several years will begin to appear yellowish-brown to tan and start to be shed from affected trees within the next two weeks or so. The great majority of infections are caused by the brown spot fungus, Lecanosticta acicola (= Mycosphaerella dearnessii), but several other fungal pathogens may also be present.  Needle shedding is expected to be heaviest throughout the month of June, and should be largely completed by the first week in July.  Affected trees will appear thin in the crowns, as the current-season needles will not yet be fully expanded.

In white pine stands that have a known history of several consecutive years of needle loss, manage carefully, and avoid thinning or other disturbance-related activities that could further weaken trees.  Current-season needles of ornamental white pines may be protected from infection with a foliar fungicide application of copper or chlorothalonil.  Applications should be made shortly after budbreak and again two weeks later, to protect the fully-elongated needles.

White pine needle disease infection levels appear to be highly regulated by wet weather; long periods of damp weather and high rainfall increase the probability of infection.  Although much of the growing season in 2015 was drier than in recent past, the month of June was wetter than normal.  2015 infection levels may remain similar to what has been seen in recent years or slightly abated.

Photo: Young white pine regeneration heavily infected with brown spot needle disease, Bethel, Maine on June 14, 2011.  (Maine Forest Service)

Winter Drying Injury – Damage attributed to winter drying injury was reported in Old Town (Penobscot County).  The landowner reported scattered balsam fir with reddened 2015 growth.  Weather conditions were consistent with those reported to predispose trees to this type of damage, specifically winter thaws cause tissues to lose hardiness and become vulnerable to injury from subsequent freezing temperatures. 

Photo: Damaged balsam fir tips, Old Town, ME (Photo: L. Beauregard).