N.C. State researchers say roach grooming could lead to new pest controls

relder@newsobserver.comFebruary 4, 2013 

Periplaneta grooming side

NCSU DEPARTMENT OF ENTOMOLOGY

— Cockroaches spend most of their time grooming, and some N.C. State University researchers think the insect’s meticulous nature could one day lead to its demise.

That would be no easy feat. Roaches are famously tough to kill. They shrug off radiation, thrive in natural disasters, even live for weeks after decapitation. No wonder they’ve been around 350 million years.

Yet scientists may have finally found an Achilles’ heel.

Their habit of incessantly cleaning themselves – particularly their antennae – keeps their senses keen but also offers opportunities for the development of pest control, said Coby Schal, an NCSU entomologist and co-author of a paper on insect grooming that appeared Monday in the online journal Proceedings of the National Academy of Sciences.

“It’s a beautiful sight, the way they bend their bodies and do all sorts of things in order to stay incredibly clean,” Schal said.

“But if we know this insect grooms all the time, we should take advantage of the behavior in ways such as how we deliver insecticides.”

Antennae are important to roaches because they allow the common household pest to smell and taste, detect humidity, feel gravity and perform a host of other sensory functions.

The constant grooming helps remove pollutants that can cling to antennae and interfere with the collection of sensory information the insect needs to behave normally.

“We found that if you prevent an insect from grooming antennae, its olfactory ability is impaired,” Schal said.

Schal also found that the grooming helps spread a type of waxy build up, known as cuticular lipids, from the antennae to the rest of the body. The wax is secreted by the insect to help protect its exposed exoskeleton.

“We hypothesized that the insect puts out the wax, and then through self-cleaning removes whatever is not needed,” Schal said. “What we found was a sort of funny trade-off: the insect has to put on waxes to protect the body from water, but not too much or it will interfere with olfaction or smell.”

Schal’s co-authors were Dale Batchelor of NCSU’s Analytical Instrumentation Facility and Marianna Zhukovskaya of the Russian Academy of Sciences.

To make their observations, the researchers restrained the insects to prevent them from grooming one of their two antennae. Then the insects were exposed to sex pheromones, food odorants and other forms of olfactory stimulation.

“When we looked at the physiological response using electrodes, it was clear that the normal antennae had much greater sensitivity than the restrained antennae,” he said.

The research findings suggest that blocking the grooming function could interfere with the insect’s ability to detect danger or find a mate, Schal said.

In addition, the grooming itself could be a way to kill the insects.

A cockroach cleans its delicate antennae by running them through its mouth. And whatever has adhered to the antennae is ingested, which is another factor with implications for pest control. If the right substance can be formulated – a dust or mist that would settle on the antennae, for example – the constant grooming may become an easy way to deliver a fast-acting insecticide.

Billy Tesh, owner of Pest Management Inc. and a member of the N.C. Department of Agriculture’s Structural Pest Control Committee, said similar research at NCSU and other places has moved the insecticide industry toward more targeted applications for various species.

“The idea is to isolate the insects’ biology and behavior to determine what will be most effective,” said Tesh. “Years ago, we just sprayed everything because we had to.”

He added that more customized insecticides reduce the amount needed.

The researchers also looked at the behavior of carpenter ants and houseflies. The insects’ sensory detection systems all were handicapped in varying ways by the inability to groom their antennae regularly, Schal said.

Elder: 919-829-4528

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