Gypsy Moth Monitoring in B.C.

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

Gypsy 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 Gypsy 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 male moths are trapped, the trap density in the following year is increased to 32 to 64 traps per square mile – a method called “delimiting trapping”. Increasing the density of traps provides a better idea of the boundaries of the area covered by the infestation.

Monitoring After a Gypsy 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 gypsy moths, the trapping density returns to monitoring levels. A population is considered eradicated after two years have passed without any moths trapped.