The Q&A Archives: How often do I use BT?

Question: I have heard from many sources to use BT for cabbage loopers, but no one had referred to the frequency of using this product. I have purchased this product, but no where on the bottle does it give how often to spray either.

Can you give me an idea on how fast I will see results, or how often I should use BT?

Thank You,

Answer: Bacillus thuringiensis (commonly called "B.t.") is bacterial pesticide. Different strains of the bacteria control different pests. B.t. var kurstaki and B.t. var berliner infect lepidopterous (caterpillars) pests and beetle larvae; B.t. var san diego infects beetle larvae; B.t. var israelensis infects fly larvae, including mosquitos. B. popillae and B. lentimorbus infect Japanese beetle grubs in the soil. Bacterial pesticides are most effective against early instar larvae. Older caterpillars, beetle larvae, etc., are more tolerant of the bacteria. B.t. must be ingested by the insect in order to infect, therefore apply only when pests are feeding actively. Once applied, B.t. products do not last long in the environment; reapplication may be necessary.

Since it's a stomach poison and must be consumed, you can reapply when new pests are found. (Usually in 5-7 days when a new generation hatches.) You should see results within 24 hours. Hope this answers all your questions!

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