Resilient Bugs
3:23 pm
Mon March 10, 2014

Invasive Bugs in Connecticut May Be Adapting to Extreme Winters

A live hemlock woolly adelgid in the spring. This winter's extreme cold has reduced population numbers statewide, but there is evidence that bugs in the northwest corner of the state are becoming more cold-weather resistant.
A live hemlock woolly adelgid in the spring. This winter's extreme cold has reduced population numbers statewide, but there is evidence that bugs in the northwest corner of the state are becoming more cold-weather resistant.
Credit Carole Cheah / Connecticut Agricultural Experiment Station

Scientists say this winter's extreme cold is having a limited impact on the state's invasive bugs, and it may even be making one insect stronger. It's called the hemlock woolly adelgid, and it was first identified in Connecticut in 1985.

Infected Hemlock trees can die off within four to six years of the adelgid's arrival.

"In the period of less than ten years it was found throughout the whole state," said Carole Cheah from the Connecticut Agricultural Experiment Station. "It kind of settles on the twig, on the hemlock twig, and spins this wool around itself, which protects it from the cold and the rain. It doesn't move, so a lot of people will think it's a fungus."

Evidence of a hemlock woolly adelgid infestation. The bugs wrap themselves in a wool-like coating.
Evidence of a hemlock woolly adelgid infestation. The bugs wrap themselves in a wool-like coating.
Credit Carole Cheah / Connecticut Agricultural Experiment Station

But it's a bug -- and it's a dangerous one. Infected Hemlock trees can die off within four to six years of the adelgid's arrival. Each year,  entomologists collect data hoping that Connecticut's cold winter weather will knock those population numbers down. "This year's data was very interesting," Cheah said. "Because of all this interest around the polar vortex, I was able to go out and sample ten sites throughout the state ...to see what effect that brief period of cold temperatures had on the adelgid."

Hemlock trees that have been inspected by the Connecticut Agricultural Experiment Station. Fewer trees may require insecticide this coming spring.
Hemlock trees that have been inspected by the Connecticut Agricultural Experiment Station. Fewer trees may require insecticide this coming spring.
Credit Carole Cheah / Connecticut Agricultural Experiment Station

Cheah found that in really cold parts of the state, like the northwest corner, bugs aren't dying off at the rates they once did. "I'm seeing populations in that part of the state which, prior to this, had suffered high mortality," Cheah said. "They're suffering much less mortality, which suggests there's some sort of adaptation going on from the survivors of previous winters. Which is not really good news."

But there is some good news. While bugs in the northwest are proving themselves more resistant, overall, the temperatures this winter did kill off about 80 percent of the state's adelgids. That means fewer hemlocks needing insecticide this spring.