Ministry of Natural Resources: LDD Moth

February 18, 2022

Dear Colleague:

Ontario is currently experiencing an outbreak of LDD moth (previously referred to as gypsy moth), particularly in southern Ontario and some areas of the northeast region of the province. Severe LDD moth infestations are cyclical, occurring every seven to 10 years, and usually last three to five years.

In the spring and early summer, LDD moth larvae consume leaves, defoliating trees and leaving them looking nearly dead. LDD prefers oak trees, but during severe outbreaks other hardwoods and, in some cases, conifer will be defoliated. Hardwood trees can produce a second crop of leaves during the growing season allowing them to continue growing and storing nutrients into the fall and winter months. Since conifers can’t produce a second crop of foliage, they may be impacted by severe defoliation. Healthy growing trees can withstand a few seasons of severe defoliation before branch and twig dieback start to occur.

In 2021, the Ministry of Northern Development, Mines, Natural Resources and Forestry (NDMNRF) conducted aerial and ground surveys to map damaged areas and forecast defoliation for 2022. The results suggest 2022 will be another year with high populations of LDD moth causing moderate to severe defoliation in some areas. Lighter defoliation is forecasted in some areas that have been impacted in previous years. NDMNRF will continue to monitor LDD moth throughout the current outbreak cycle.

Although the ministry conducts pest management programs on Crown land to protect foliage of high-value stands (e.g., jack pine and spruce budworm programs), management of LDD moth on private land is the responsibility of the landowner or municipality. The ministry supports these efforts by providing information on forest pests and options for reducing defoliation by LDD moth. Ontario’s Invasive Species Centre also offers resources and information to help people prevent LDD moth from damaging their trees.

In the spring, landowners can put bands of burlap around their trees. This gives the larvae a place to congregate during warm days and they can be physically removed and killed. In the fall, landowners can remove and destroy egg masses.