Lymantria moth monitoring in B.C.

To eradicate introduced Lymantria moth (formerly referred to as gypsy moth) populations, the B.C. Government needs to know the location and size of a population. Lymantria moth monitoring, using traps to find moths, is conducted each year in high-risk areas across southern B.C.

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Lymantria moths are monitored using pheromone traps that are effective in attracting males. Traps are placed in early summer, well before the expected flight period in late July through August. When adult male moths are caught, their location and the locations of all traps are plotted on maps. These data points are used to establish further monitoring and treatment efforts.

The exact number of traps and where they are placed is determined each year by the Lymantria Moth Technical Committee of the B.C. Plant Protection Advisory Council (BCPPAC). This monitoring program is conducted by the Canadian Food Inspection Agency (CFIA), which places traps throughout the province in cooperation with government.

Basic monitoring

For basic monitoring, typically no more than one trap is placed per square mile.

Monitoring after at least one male moth is trapped

If at least one male moth is trapped, the trapping density is increased the following year to 32 traps per square mile within a half-mile radius of the positive detections.

Monitoring after a Lymantria moth treatment

In the first year, the density of traps remains high at 32 to 64 traps per square mile within the treated area, and 16 traps per square mile within a half-mile radius.

In the second year, trap density is reduced to 16 per square mile.

In the third year, trap density returns to 1 per square mile.

After the area has been declared free of Lymantria moths, the trapping density returns to monitoring levels. A population is considered eradicated after two years have passed without any moths trapped.