Gypsy Moth Egg Mass Survey Predicts More Defoliation in 2019

24 Jan

Forest Health staff from the Department of Conservation and Recreation have completed a survey counting gypsy moth egg masses. Results show that some areas may be in for severe defoliation in 2019. Due to the strong influence of natural conditions and controls, it is difficult to predict gypsy moth impact on a local level, but the egg mass survey gives a rough idea of potential damage we might expect for parts of the state in 2019.

The current outbreak began in 2015, with the population increasing through 2016 and leading to over 923,000 acres of defoliation in 2017. High caterpillar mortality in 2017 from the Entomophaga maimaiga fungus and the Nuclear Polyhedrosis Virus (NPV) led to reduced feeding pressure in 2018, which in turn caused a decreased impact, about 161,000 acres of defoliation statewide.

However, there was very little caterpillar mortality in 2018 and there was high moth reproductive success. In many areas across the state, foresters have documented high densities of egg masses. We are expecting the outbreak to continue in 2019 with regionalized pockets of defoliation present in Essex, Hampden, Hampshire, Middlesex, Norfolk, Plymouth, and Worcester Counties.

To find out more, go to the Gypsy Moth in Massachusetts guide at

In southern Worcester County and eastern Hampden and Hampshire counties, repeated defoliation of oaks has resulted in considerable mortality.  The Worcester Telegram ran an article featuring many MFA members about the problems for landowners in trying to salvage oaks.

To read the article, see