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"Bt"...nontoxic insecticide.

"Bt' . . . nontoxic insecticide

The nontoxic insecticide with the tongue-twister name, Bacillus thuringiensis has come a long way. Popularly known at Bt, it is more widely available than ever in nurseries and garden centers. One variety --B.t. kurstaki--is a more potent form.

A newer introduction--B.t. israelensis-- specifically attacks mosquitoes.

For two decades, many gardeners concerned with chemical toxicity sprayed the bacteria Bacillus thuringiensis to destroy certain caterpillars and worms. Because it's not a chemical, it harms only those with alkaline stomachs. This includes many leaf chewers.

The bacteria don't kill instantly, but they ruin the digestive processes of these pests, causing them to starve to death within a day or two.

While more Bacillus thuringiensis advances are coming (researchers are developing new strains, including one that kills beetle grubs), these three forms are sold under various brand names.

Bacillus thuringiensis. Long sold as Dipel or Thuricide, this basic kind kills cabbage looper, oak moth caterpillar, sod webworm, tent caterpillar, tomato hornworm, and related caterpillars and worms. It is sold as a liquid (about $5 for 8 ounces) or as a powder (about $6 for 3 1/2 ounces) to mix with water for spraying.

B.t. kurstaki. Often sold as a sod web-worm control, this more potent type of Bt knocks out the same pests. This power costs more initially (about $10 for 4 ounces), but you use less.

B.t. israelensis. This controls mosquitoes by attacking their larvae. Sold as a powder (about $10 for 4 ounces) to mix with water and spray on ponds or puddles where mosquitoes breed, it also comes in hard rings (about $10 for five) to toss into standing water.

Photo: Various forms of insecticide are Bacillus thuringiensis (liquid and white powder), newer B.t. kurstaki (tan powder), and B.t. israelensis (doughnut-shaped rings)
COPYRIGHT 1986 Sunset Publishing Corp.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1986 Gale, Cengage Learning. All rights reserved.

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Title Annotation:Bacillus thuringiensis
Publication:Sunset
Date:Jun 1, 1986
Words:301
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