Gypsy Moths Beware

Study shows the enemy pathogens of destructive gypsy moths follow the insects’ migration closely, helping keep populations in check.


| June 18, 2010



Adult gypsy moths, with the male on the left and the female on the right.

Adult gypsy moths, with the male on the left and the female on the right.

USDA APHIS PPQ Archive/Bugwood.org

Ithaca, New York – If you live in a section of the country where gypsy moths are a relatively new menace, have no fear, help is not far behind.

Cornell University entomologist Ann Hajek told participants at a recent national conference that when the gypsy moth – whose caterpillars have defoliated entire forests – started spreading westward more than 100 years ago from New England to Wisconsin, its fungal and viral pathogens followed close behind.

“We were pretty surprised,” Hajek says. “No one knew how long it took the pathogens to chase their hosts.”

The findings are important because gypsy moth populations can develop unpredictably and erratically, with lots of caterpillars eating all the leaves off of most of the trees, Hajek says. She was speaking at the Cornell-hosted Eighth Annual Ecology and Evolution of Infectious Disease workshop and conference in early June in Ithaca. Land managers, she says, can rest assured that pathogens will follow the migrating moths, providing natural controls.

Gypsy moths are slowly moving west across the United States after being introduced to Massachusetts from Europe in 1869. They migrate slowly because the females do not fly. By tracking the edges of the migration, where population densities are low, researchers have an opportunity to investigate how long it takes their viral and fungal pathogens to catch up, Hajek says.

The fungal pathogen, entomophaga maimaiga, was first reported in 1989 and attacks the caterpillars. The virus, lymantria dispar nucleopolyhedrovirus, which was accidentally introduced near Boston in 1906, also infects gypsy moth caterpillars.





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