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Pest Control with Bacillus thuringiensis

By Eric Vinje, Planet Natural

Bacillus thuringiensis (Bt) is one of the oldest bacteria used for natural insect control. It consists of a spore, which gives it persistence, and a protein crystal within the spore, which is toxic. That toxic protein differs, depending on the subspecies of Bt producing it, yielding a variance of Bt toxic to different insect species. The toxic crystal, when ingested by the appropriate insect pest, blocks the system which protects the pests stomach from its own digestive juices. The stomach is penetrated, and the insect dies by poisoning from the stomach contents and the spores themselves.

Bt kurstaki (Bt-k) - Bacillus thuringiensis var kurstaki
Bt-k is a naturally occurring soil bacteria ideal for controlling tent caterpillars, gypsy moth, cabbage looper, tomato hornworm and other leaf eating caterpillars on trees, shrubs, tomatoes and other vegetables. Bt-k is most effective when applied to caterpillars during their 1st and 2nd instars, when they are still small. It must be ingested by the insect, as it is a stomach toxin. Harmless to humans, animals and beneficial insects. Bt-k biodegrades quickly in sunlight and may require reapplication under heavy insect pressure. To maximize effectiveness apply in the late afternoon.

Bt israelensis (Bt-i) - Bacillus thuringiensis var israelensis
Bt-i is a highly specific biological pesticide for use against mosquito, black fly and fungus gnat larvae. It may be applied safely to irrigation and roadside ditches, pastures, marshes and ponds, water gardens, flower pots, bird baths, rain gutters...any place there is standing water! Once ingested, Bt-i kills 95-100% of mosquito larvae within 24 hours. Highly effective because it kills these pests before they become biting adults. Will not harm people, pets, wildlife or fish. Mosquito Dunks are a commercial form of Bt-i.

Bt san diego (Bt-sd) - Bacillus thuringiensis var san diego and Bt tenebrionis (Bt-t) - Bacillus thuringiensis var tenebrionis
The Colorado potato beetle has developed unprecedented resistance to multiple applications of chemical insecticides. Bt-sd and Bt-t are toxic to a limited range of leaf-eating beetle species and are now considered to be the most effective control for this destructive insect pest. Can also be used to control the elm leaf beetle and may be used on potatoes, egg plant, tomatoes and elms. These biological pesticides should be applied to the young larval stages, as they have no effect on adult beetles. Safe for people, pets, wildlife or fish.

Bacillus popilliae
The milky spore disease of the Japanese beetle was the first microbial control to be developed commercially. Milky spore is the name of the disease to which Japanese beetle larvae succumb when attacked by Bacillus popilliae. The bacteria spreads naturally as each infected beetle larvae dies, decomposes and releases billions of new spores into the soil. Time must be allowed for this process to completely saturate a treated area, but only one application is required and the spores continue to multiply on their own, as long as larvae are present. When there is no longer a grub infestation, the spore remains dormant, waiting for subsequent populations.