''Bacillus thuringiensis'' subsp. ''kurstaki'' (Btk) is a group of bacteria used as biological control agents against

lepidoptera Lepidoptera ( ) is an order (biology), order of insects that includes butterfly, butterflies and moths (both are called lepidopterans). About 180,000 species of the Lepidoptera are described, in 126 Family (biology), families and 46 Taxonomic r ...

ns. Btk, along with other ''B. thuringiensis'' products, is one of the most widely used biological pesticides due to its high specificity; it is effective against lepidopterans, and it has little to no effect on nontarget species. During sporulation, Btk produces a crystal protein that is lethal to lepidopteran larvae. Once ingested by the insect, the dissolution of the crystal allows the protoxin to be released. The toxin is then activated by the insect gut juice, and it begins to break down the gut. Btk is available commercially and is commonly known as "Garden Dust" or "Caterpillar Killer", both of which are produced by Safer Brand. Other Btk-producing companies include Bonide and Monterey.

Effects on nontarget species

Btk is generally regarded as environmentally safe, as its toxicity is essentially limited to its target pest; humans, wildlife, and beneficial insects are regarded as unaffected by the pesticide. Even so, in 2012, a regulatory review of several strains of Bt by the European Food Safety Authority stated that although there was data supporting the claims of low toxicity, the data was insufficient to prove the claims conclusively.

Humans

In studies of the effects of Bt on humans, most subjects were unaffected when exposed to Bt. Some individuals reacted with

irritation Irritation, in biology and physiology, is a state of inflammation or painful reaction to allergy or cell-lining damage. A stimulus or agent which induces the state of irritation is an irritant. Irritants are typically thought of as chemical age ...

of the eyes and skin. Other subjects with

hay fever Allergic rhinitis, of which the seasonal type is called hay fever, is a type of inflammation in the nose that occurs when the immune system overreacts to allergens in the air. Signs and symptoms include a runny or stuffy nose, sneezing, red, i ...

reported more significant effects, including throat irritation, upset stomach, and difficulty sleeping.

''Trichogramma'' wasps

'' Trichogramma'' is a genus of parasitoid wasp whose females lay their eggs in the eggs of their hosts; after killing the host, an adult wasp emerges. For this reason, ''Trichogramma'' are often used as a biological control agent, and it can even be used in conjunction with pesticides like Btk. In November 2015, a study was conducted examining the effects of Btk on '' T. chilonis'' wasps. The study showed that high doses of strains of Btk containing δ-endotoxins were acutely toxic to the wasps, while Btk without these toxins had no adverse effects. It further showed that low doses of Btk, regardless of the strain, led to significantly greater longevity in the wasps.

Soil

In a 1998 study, Btk was added to different types of soil in order to determine how the type of soil affected the persistence and concentration of Btk. The results of the study showed that insecticidal activity started to decline after only a month in one soil, while in another toxicity was still high after six months. The authors of the study noted that even though Btk is considered non-toxic to nontarget species, the accumulation and persistence of the Btk toxins could eventually lead to environmental hazards or the selection of Btk-resistant lepidopterans.

References

External links

Btk fact sheetBt fact sheet
{{Taxonbar, from=Q24977208 thuringiensis kurstaki Biopesticides