Evaluation of Biorational Insecticides for Management of Euproctis chrysorrhoea (Lepidoptera: Erebidae).

The browntail moth (Euproctis chrysorrhoea L.) is an invasive species which over the past five years, has been undergoing outbreaks on a scale not seen in the northeastern U.S. in over 100 years. Browntail moth larvae feed on and defoliate a number of deciduous tree species, but the health issues caused by contact with the toxic urticating hairs of the overwintered larvae have resulted in very low tolerance for this pest amongst homeowners and land managers. Few recent studies have been conducted to assess management options for browntail moth, which is abundant in ecologically sensitive areas along coastal waters, and around people's homes. We investigated the potential to manage overwintered larvae with currently available biorational insecticides. Laboratory bioassays revealed susceptibility to Beauveria bassiana (Balsamo) Vuillemin (Hypocreales: Cordycipitaceae), Bacillus thuringiesis kurstaki (Berliner), azadirachtin, and spinosad products. A field trial was conducted to assess efficacy of B. bassiana, Btk, and azadirachtin. All treatments reduced the abundance of larvae compared with the control, but only two applications of Btk and single application of a tank mix of B. bassiana and Btk reduced pupal nest abundance. A laboratory experiment revealed that temperature did not affect the feeding and survival of larvae exposed to the field trial foliage from the Btk and the Btk/B. bassiana tank mix treatments, whereas slower feeding rates and increased time to death were observed with the control and B. bassiana alone treatment.

Factors Influencing the Population Fluctuations of Euproctis chrysorrhoea (Lepidoptera: Erebidae) in Maine.

The browntail moth (Euproctis chrysorrhoea (L.)) is a forest pest that was accidentally introduced in the late 1800's and spread throughout New England in the early part of the 20th Century. At its peak range expansion in 1915 it encompassed an area of 150,000 km2 after which populations declined. By the 1960s, its distribution had receded to relic populations on outer Cape Cod, MA, and islands in Casco Bay, ME. In 1989 browntail moth resurged in Maine, with periodic, moderate outbreaks before a dramatic increase of the population occurred in 2016. We examined the pattern of annual defoliation by browntail moth since its resurgence in the 1990s as well as variation in populations throughout infested areas in Maine during three years of the recent outbreak, 2016-2018, relative to differences in weather, parasitism and habitat characteristics. Levels of defoliation over 24 yr were predicted by the preceding spring precipitation (-, negative effect) and the year's previous late summer and early fall temperatures (+, positive effect) when first to third instar larvae feed and then construct winter hibernacula. Late summer temperatures predicted the abundance of hibernacula across outbreak areas (+). Early spring temperatures (+) and early and late spring precipitation (-) predicted early summer larval and pupal nest abundance. Warmer fall temperatures result in more mature populations coming out of winter hibernacula in the spring, whereas spring precipitation drives epizootic outbreaks of Entomophaga aulicae (Reichardt in Bail) Humber (Entomophthorales: Entomophthoraceae). with parasitoids playing a lesser role. Climate trends indicate continued increases in fall temperatures since browntail moth resurgence.