It’s about to begin. In a couple of weeks here in southern New England, (late November), we’ll start to notice clouds of dull gray brown moths fluttering about at night, attracted to the glow of porch and street lights. Mating season for the Winter Moth, Operophtera brumata, is about to begin as both male and female moths emerge from their pupae. They will procreate into December, or as long as mild enough temperatures prevail.
In our recent research for the best methods to combat this destructive pest (Winter Moth caterpillars devour new plant growth on many of our most highly desirable ornamental trees and shrubs), we came across great news! University of Massachusetts Entomologist Joe Elkinton and his team have solid evidence that a parasitic fly, Cyzenis albicans, is an impressive natural control for Winter Moth. At four test sites where the parasite has been released throughout southeastern MA (Seekonk, Hingham, Falmouth and Wellesley) populations of winter moth have dramatically decreased. Here is a link to an article.
Isn’t that fantastic to read? However, while we are waiting for this helpful parasitic fly to move into our neighborhoods, we must begin preventive measures. It is necessary to understand the Winter Moth lifescycle to plan and time your defense. The first meaure is to apply sticky tree bands around treasured specimens, which trap the females as they adhere and climb up tree trunks, emitting their sex pheromone to attract the males. After the mating scene has occurred, female moths continue to climb to the top of trees and shrubs and then lay their eggs in the bark and crevices near branches. Adult moths die at this stage.
Other types of botanical controls can be applied over the winter and early spring. In late winter, dormant oil spray can be applied to branches to suffocate the eggs. In early spring, Bacillus thuringiensis a.k.a. BT, a beneficial bacteria, can be used to effectively control the caterpillars as they emerge from their egg sacs and seek nourishment from the young unfurling foliage. Spinosad is another bio insecticide, and is available to homes owner under product labels Monterey Garden Insect Spray and to licensed pesticide applicators as the product Conserve. Care should be taken to avoid applying Spinosad when bees are active.