Auburn research finds kudzu bugs affected by persistent cold

By James Langcuster, Auburn University Communications

If Old Man Winter deserves credit this year for reducing kudzu bugs, it is not so much due to his bite as to his persistence.

For the past few years, Dr. Xing Ping Hu, an Alabama Extension entomologist and Auburn University professor of entomology, and a team of researchers have been monitoring overwintering kudzu bug populations.

Fewer Kudzu Bugs in the Spring

She has concluded that there will be fewer of these malodorous pests to see and smell this spring.  Hu attributes the cause of these reduced numbers to this winter’s endurance rather than to its severity.

Until early last month, Hu and her researchers noted little difference in the mortality rates in overwintering kudzu bugs compared with 2013.

“We noted in 2013 that some of the bugs emerged out of the dormant status of hibernation too early, used their energy and died when the temperatures dropped again in early February,” Hu recalls. “But then warmer temperatures set in and the insects rebounded.”

Hu initially expected the bugs to exhibit similar levels of resilience this year.   More of the kudzu bugs remained in their dormant status, with the ones hibernating underneath thick bark, vines and trees afforded the best protection against the cold.

Marked Changed after Early February

But things began to change markedly after early February.  Old Man Winter proved especially dogged and the chilling temperatures persisted.

That was the big difference between February, 2013, and last month.  As freezing weather persisted, more of the hibernating bugs began dying.

“Our last survey on March 7 revealed that more than 90 percent of overwintering bugs had died, compared to 70 percent in 2013,” Hu says, adding that males have suffered higher mortality rates than females.

Hu and the others have noted another telltale sign: Fewer of the bugs are flying out and mating as spring approaches.

“We’re noticing that most of the survivors are still in dormancy — a significant change from 2012 and 2013, when significantly larger numbers were observed emerging from their long slumber and flying out to mate as mid-March approached.”

Persistently cold temperatures are the reason, Hu contends.

While there was a couple of freezing cold days in February, 2013, namely February 22 and 23, there were long stretches of warm days too.

This year’s winter has been unusually and, most important from the standpoint of kudzu bugs, persistently cold.  Equally significant, there were fewer days that reached into the 70s.

The end result will be fewer kudzu bugs this spring, Hu says. Even so, despite the havoc this prolonged winter has played on spring kudzu bug numbers, Hu says the populations may increase quickly in the summer and fall, thanks to the pest’s immense reproductive capacity.

Other Insights into Kudzu Bug Behavior

In the course of investigating these overwintering bugs, she and her team have uncovered a few other insights into the pest’s behavior.

For example, both male and female adults overwinter in dormant states of hibernation.

“Our field observations reveal that the bugs feed on all kinds of plants to store food reserves later in the fall and then begin searching for protective places to overwinter — typically under tree bark and in and under tree litter.

She and other investigators also have observed that overwintering populations may come out flying during the hibernation period when warmer days exceeding 70 degrees arrive. But they pay a heavy price for giving in to this false sense of spring.

“The cost of this behavior is a reduction in energy reserves and survival because there is no food available, even though they will have to go back to hibernating when the temperatures drop again.”

This research was funded by a Southern IPM Center IPM Enhancement Grant.

Other Insects Not Affected

Hu and her researchers have uncovered no evidence that other pesky insects such as fire ants, termites and carpenter bees have been similarly affected by the prolonged cold.

“We’ve observed new fire ant mounds popping up in fields and yards and a few kicks to mounds arouse hundreds of ants,” Hu says.

Termites have also been observed thriving in fallen logs and under tree bark.

And what about those industrious and persistent carpenter bees?  Hu and her team have observed them emerging from their galleries to begin their unrelenting search for flower pollens.

Homeowners should expect their peak foraging period to begin later this month, she says.

Read the original release, with photos.

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