Tuesday, August 10, 2010

RESEARCH ON INSECT HIBERNATION MAY LEAD TO NEW CONTROL MEASURES



To beat summer heat, winter cold and other harsh environmental conditions, many insects temporarily drop into a state similar to hibernation to conserve energy and reduce stress, and University of Florida researchers say this phenomenon could lead to new pest control methods.

A UF study published in the current issue of the Proceedings of the National Academy of Sciences shows that different organisms use different mechanisms to reach that resting state, known as diapause.

Scientists are exploring the biochemical processes behind diapause as a first step toward manipulating when and how diapause occurs in pest insect species, said Dan Hahn, an assistant professor with UF’s Institute of Food and Agricultural Sciences.

“If you can disrupt diapause, you can change the chances an insect population survives,” Hahn said.

Hahn and postdoctoral associate Greg Ragland have set their sights on two notorious pests: the apple maggot fly, which attacks apples, cherries and blueberries, and the corn earworm, which attacks more than 100 crops, including sweet corn.

Florida is the nation’s No. 1 producer of fresh sweet corn and accounts for about 20 percent of national sweet corn sales. Sweet corn ranks among the state’s top four most valuable vegetable crops, and the corn earworm is one of its most damaging pests.

Diapause helps insects stay synchronized with natural cycles such as temperature, rainfall and food availability, to increase their chances of survival, Hahn said. Pest control applications would involve starting or stopping diapause at times not beneficial to pests. For example, by exposing insects to a chemical that stops diapause, it may be possible to “wake them up” when no is food available, dooming entire populations to starvation.

In the study, Hahn, Ragland and colleague David Denlinger of The Ohio State University studied genes and biochemical pathways involved in diapause for an insect called the flesh fly, which typically feeds on carrion, dung or decaying material.

The flesh fly has little economic impact, but it’s widely used in scientific studies and is one of the few invertebrates that has been investigated for its diapause traits.

The UF team also studied two other commonly researched species whose diapause traits are known: a fruit fly and a nematode. When the team compared the biochemical pathways controlling diapause in those two organisms with those in the flesh fly, they were surprised to find each pathway was different.

Diapause is apparently such a useful trait that it evolved independently in numerous species, Ragland said.

“So, you end up with multiple routes to the same end point,” he said.

One common factor: all three organisms experienced a slowdown in metabolism, presumably to conserve energy.

Eventually, detailed knowledge about the biochemical pathways could enable scientists to design highly specific pesticides that affect only one species, and also broad-spectrum pesticides that affect many species, Hahn said.

The UF study is significant because it’s one of the first comparisons of diapause among different invertebrate species, said Peter Armbruster, a biology associate professor at Georgetown University in Washington, D.C.

As a result, the study provides a more comprehensive picture of the processes involved in diapause and will be useful to researchers in the future, said Armbruster, who studies diapause in mosquitoes.

(Photo: Tyler Jones, University of Florida/IFAS)

University of Florida

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