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Super-slurper cocktail helps rout weevils.

Super-slurper cocktail helps rout weevils

An estimated 80,000 acres of Florida citrus groves are currently infested with weevils. Among the more devastating is Diaprepes abbreviatus, also known as the sugar-cane root-stalk weevil. The mature insect attacks orange and grapefruit foliage; its soil-foraging larvae have a predilection for the roots of citrus trees. Within two years, an infested grove can suffer such extensive damage that costs of treating affected trees can equal or surpass the value of their fruit, according to William J. Schroeder, an entomologist at the U.S. Department of Agriculture (USDA) Horticultural Research Laboratory in Orlando, Fla. Without treatment, weevils will kill 20 to 30 percent of a grove and render the remaining trees unable to bear fruit.

What's a citrus grower to do? Mix his trees a watery cocktail laced with nematodes (soil roundworms that harbor bacteria lethal to weevil larvae) and microscopic flakes of the USDA-patented polymer known as "super slurper." In preliminary experiments, Schroeder has demonstrated that this very low-cost insecticide can rout 60 percent of infesting weevils.

Once a nematode enters a larva, its bacteria get right to work, killing the weevil within 24 hours. But Schroeder found that the dry, quick-draining sandy soils typical of most Florida groves can't sustain the moisture-loving host worms throughout dry spells. So Schroeder enhances the soil's water-holding ability with the biodegradable cornstarch-based super slurper; it can absorb up to 2,000 times its weight in water.

One liter of Schroder's weevil-killing cocktail contains water, 5 grams of the starch and about 5 million nematodes. It can be applied to the roots of a tree at planting, or sprayed directly onto the soil under a tree. Schroeder has applied for a patent on this super-slurper application and expects to pilot test it in groves this year. If all goes well, he says, the technology could be commercially introduced within two years. Other USDA labs are looking to adapt this cocktail to control corn and vegetable pests.
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Publication:Science News
Date:Apr 23, 1988
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