St. Clair Township Crest
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Ministry of Northern Development, Mines, Natural Resources and Forestry

Ministere du Developpement du Nord, des Mines, des Richesses naturelles et des Forets

Office of the Minister

99 Wellesley Street West Room 6630, Whitney Block Toronto ON M7A 1W3 Tel: 416-314-2301

Bureau du ministre

99, rue Wellesley Quest Bureau 6630, Edifice Whitney Toronto ON M7A 1W3
Tel.: 416 314-2301

Ontario

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.

Landowners wishing to reduce impacts on their property can also have trees sprayed with Btk (Bacillus thuringiensis kurstaki) in the spring by a licensed insecticide application company. This is best carried out by coordinating efforts with other local landowners. Landowners can check their local listings for a reputable insect control provider in their area.

In the past, demand for aerial spraying of LDD has exceeded industry capacity. If landowners are considering having their property sprayed, it is best to engage a licensed insecticide application company as early as possible.

There are also natural controls on LDD moth populations in Ontario:
• Cool, wet conditions provide an ideal environment for a natural fungus (Entomophaga maimaiga) known to contribute to LDD moth population collapse.
• A viral infection (nuclear polyhedrosis virus or NPV) also kills LDD larvae.
• There are other natural enemies of LDD moth as well, including parasitic insects and predators such as birds and mammals.

I have attached a fact sheet and a roles and responsibilities document to help your office assist your constituents who may have questions about managing LDD moths during the outbreak period.

Sincerely,

The Honourable Greg Rickford
Minister of Northern Development, Mines, Natural Resources and Forestry Attachments