European Gypsy Moth

European Gypsy MothThe European Gypsy Moth is a non-native defoliating insect that feeds on a variety of tree species found in southern Ontario. In Brantford and surrounding areas, the European gypsy moth can be problematic in forested areas with oak dominant communities such as Mohawk Park.

Accidentally introduced in North America from Europe and Asia in the 1860s, the European gypsy moth has thrived with limited predators and can be destructive to local ecosystems. The moth is of concern because during the larva stage of the insect, the caterpillar eats the leaves of trees, defoliating them which in turn may make them more susceptible to disease and damage from other insects.

European Gypsy Moth - DeforestationAlthough the caterpillars feed on a wide range of hardwood and evergreen trees, they show a preference for certain species such as poplar, birch and oak trees. Every 8-12 years when conditions are suitable, significant increases in populations of gypsy moths occur. These outbreaks can cause large holes in the leaf surfaces or completely defoliate trees and shrubs in large areas. Continued defoliation of trees can lead to their decline and eventual death.

The last outbreak of European gypsy moth in Mohawk Park occurred in 2007. An increase in the population in 2020 has resulted in many trees in Mohawk Park losing their leaves.

Pest Management

European Gypsy Moth - TrapsGypsy moth outbreaks may appear suddenly and may continue for several years in any one location. Natural control factors such as disease, parasites and predators eventually combine to cause a collapse of these outbreaks. Consecutive years of gypsy moth infestation can cause severe defoliation which can lead to tree mortality. Intervention may be required to control continued outbreak levels of gypsy moth in areas with trees that are at risk of mortality if no action is taken. Eradication of gypsy moth is not a realistic management objective since it is well established throughout North America.

Several strategies to address the pest population may be necessary. Strategies that are the least harmful to the environment are initiated first. Although insecticides applied to foliage can be effective, at this time aerial spraying is not being considered. Other strategies include the installation of pheremone traps, removal of egg masses ( where possible) and in some cases biological controls.

A pheromone trap hanging in a tree. These traps release a chemical to attract male gypsy moths where they’re trapped before they can mate with the female moths (and produce the next generation of caterpillars). Look for these traps in Mohawk Park this year.

Lifecycle:

The gypsy moth’s lifecycle is important in managing its impact. There are four main stages of the gypsy moth lifecycle:

  1. Egg
    • Late August to early May
    • Stage lasts eight months
    • Dormant, over-wintering stage
    • Egg masses range in size from 2-8 cm long and can contain between 100-1000 eggs

      European Gypsy Moth - Eggs
  2. Caterpillar
    • Early May to mid-July
    • Stage lasts 40 days
    • Tree-damaging stage
    • A single caterpillar can eat an average of one square meter of foliage. They continue to feed, moult, and feed until they are about six to seven centimetres long. Once they’ve finished feeding, they seek shelter to cocoon

      European Gypsy Moth - Caterpillar
  3. Cocoon
    • Mid-July to early August
    • Stage lasts 10 to 14 days
    • Transformation stage
    • After the adult moth emerges, it leaves the empty cocoon behind. The female cocoon is larger than the male cocoon.

      European Gypsy Moth - Cocoon
  4. Moth
    • Late July to mid and late August
    • Stage lasts 10 days
    • Reproductive stage

      European Gypsy Moth - Moth

An adult gypsy moth’s only function is to reproduce. Unlike other species of butterflies and moths, adult gypsy moths do not eat anything. The female is larger than the male and is cream coloured. The female moths cannot fly. Instead, she uses pheromones to attract male moths. Male moths are smaller and brown in colour.

Resources: https://www.ontario.ca/page/gypsy-moth