Moth News

To the Editor:

The trees in Mattapoisett and neighboring towns were pummeled this year by both winter moth and gypsy moth caterpillars.

We were somewhat lucky with the gypsy moths because their nemesis, Entomophaga maimaiga (an insect-attacking fungus), had just the right amount of moisture to become active and fatally infect large numbers of the adult caterpillars. If you saw the dead fuzzy caterpillars hanging by one end from the trunks of your trees, then it is likely that the fungal spores got to them and will be around in leaf litter for next year to keep the gypsy moths in check. Let’s hope so. Odds improve if you leave fallen leaves undisturbed around trees.

As for the winter moths, we haven’t been lucky at all, at least not yet. But there is cause for hope and there are things that you can do to protect your trees. Unintentionally introduced in Massachusetts from Europe and first identified here in 2003, the defoliating winter moth caterpillar has no local predators or parasites. The adult moths emerge from the ground and mate from late fall until freezing temperatures kill the adult population. Females, which cannot fly, climb and deposit their eggs on the bark and branches of trees. The eggs overwinter and emerge as tiny caterpillars in springtime just as trees and other plant material are breaking bud in late March to mid-April. Caterpillars feed on the buds and developing leaves resulting in defoliation and stress to trees and neighboring plants. As they feed and grow, they “balloon” on long silken strands from tree to tree in search of food. Most damage is done by late May into early June when trees struggle to refoliate or simply give up and succumb after successive years of caterpillar attacks. Damaged trees need extra water to aid in making new leaves but they should not be fertilized at that stressful time.

The winter moth does have a predator that naturally keeps it in check in Europe, and UMass entymologist Dr. Joseph Elkinton has been breeding and releasing the Cyzenis albicans fly in winter-moth affected areas of Massachusetts. The fly parasitizes winter moth eggs and they make a near-perfect pairing. Previous successful fly introductions in winter-moth affected areas including Nova Scotia and Wellesley took about six years to colonize and control winter moth infestation. Around a thousand of these flies were released in Mattapoisett’s Nasketucket Bay State Reservation in 2013. The Elkinton lab checks release sites yearly looking for established populations by collecting winter moth larvae for signs of the flies. The flies haven’t taken hold yet in Mattapoisett but, if colonization occurs, it will take a few more years for them to spread to surrounding areas.

Don’t give up on your trees in the meantime. You have options that include spraying and banding but neither method is perfect. Spraying is effective but is best left to professionals and that can be expensive. Application must be correctly timed to target the appropriate stages of the moth’s development. Unintentional harm to bees and other pollinators can result if spraying of lethal agents is done at the wrong time. Tree banding, which is a physical sticky barrier that acts like fly paper, is another option that can at least put a dent in the moth population without chemicals as we wait in hope for the Nasketucket flies to find their way to the rest of the town’s trees. The Mattapoisett Tree Committee, in consultation with Tree Warden Roland Cote and in partnership with the Mattapoisett Land Trust, will present a tree-banding workshop in October to demonstrate a technique to trap winter moths after they emerge from the ground this fall but before they can climb trees and lay eggs for a new generation of caterpillars. The workshop will take place on Saturday, October 17 at the Land Trust’s property at Dunseith Gardens at 1:00 pm. Rain date is October 18.

If you would like to attend this free workshop, then contact the Mattapoisett Tree Committee at MattapoisesttTreeCom@gmail.com or like us on Facebook at MattapoisettTreeCommittee for updates on our work to protect and encourage trees in Mattapoisett.

Deborah Smiley, Mattapoisett Tree Committee

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