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UC IPM Home > Home,
Gardens, Landscapes, and Turf > Pesticides > Bacillus
Thuringiensis
How to Manage Pests
Pesticide Information
Bacillus thuringiensis kurstaki
Type
Microbial insecticide.
Plant uses
Ornamentals, fruit trees, vegetables.
Pests controlled
Leaf- or bud-feeding caterpillars (the larvae of moths
and butterflies). Smaller larvae are more susceptible; caterpillars
must eat treated plant surfaces to be killed.
 Hazards to people
Low. May cause skin or eye irritation.
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Hazards to wildlife
None to low. Larvae of desirable butterflies will not be injured if their food sources are
not sprayed. Few desirable butterflies feed on vegetables or fruit trees or the most common cultivated ornamentals.
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Hazards to beneficials
Low.
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Potential period of activity after treatment
Breaks down rapidly: 24 to 48 hours after application.
Precautions and safety equipment
Minimize your exposure to pesticides. Wear long pants, and a long-sleeved shirt. Keep dust out
of eyes with
goggles or glasses.
Active ingredient
Bacillus thuringiensis, kurstaki strain, is a naturally occurring bacteria that causes disease
only in the larvae of moths and butterflies. A toxic protein crystal produced by the bacteria is responsible for
the insecticidal effect.
Application tips
Surfaces where caterpillars feed must be well covered
because caterpillars must ingest the bacteria to be affected. Careful
timing is essential for success. Apply just after caterpillars begin
hatching out of eggs. Small caterpillars are more susceptible than older
larvae. Treatment is not effective on eggs, pupae, and adults. The material
breaks down rapidly in the environment. Try to avoid making applications
when the sun is on the plant. Affected caterpillars will stop feeding
within hours, but may not die for 2 to 3 days. Wettable powders that
you mix up yourself just prior to application will be most effective.
Make up a fresh solution each time you treat. Reapplication will be
necessary to kill caterpillars hatching one or more days after an application
is made.
Always check the label before purchasing or applying a pesticide product for a specific pest on a specific plant
to be sure it can be applied. Follow label directions precisely.
WARNING ON THE USE OF CHEMICALS
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