Along Came A Spider...and "Sat Down" Some Crop Pests

By Hank Becker
August 3, 1998

Few tiny creatures are as hugely feared as spiders. But scientists at the Agricultural Research Service believe native spiders deserve more respect--instead of neglect--as natural pest controls. The scientists' new biochemical tests can tell what the spider--or other tiny predator--ate for lunch.

They used one of the tests to discover that winter spiders (Chiracanthium innclusum) may be helping cotton growers. It revealed that eggs of two cotton pests had been on the menus of about one-fourth of the winter spiders collected in a Georgia cotton field.

ARS entomologist Matthew H. Greenstone in Stillwater, Okla., other ARS researchers and their colleagues have been pioneering the new tests, which follow an approach called serological analysis. This means using monoclonal antibodies--custom-designed molecules--to identify a prey's remains in a predator's gut. The researchers say this is the most direct way to gather long-term data on predation.

One of the new tests can distinguish the cotton bollworm from its cotton-infesting cousin, the tobacco budworm, in the guts of spiders.

In Colorado, the scientists conducted the first North American survey for spiders that kill cereal aphids and other wheat pests. Then they began devising monoclonals to learn which spiders--and other predators--eat greenbugs, Russian wheat aphids and corn leaf aphids. All three are major pests of cereal crops. The scientists are also collaborating on other monoclonals that will help in gauging how well predators suppress cereal aphids around the world.

A story about the new tests appears in the August issue of Agricultural Research magazine.