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

biological control Biological control or biocontrol is a method of controlling pests, such as insects, mites, weeds, and plant diseases, using other organisms. It relies on predation, parasitism, herbivory, or other natural mechanisms, but typically also i ...

agents against lepidopterans. 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 In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, ...

, Btk produces a crystal protein that is lethal to lepidopteran larvae. Once ingested by the insect, the dissolution of the crystal allows the

protoxin Toxication, toxification or toxicity exaltation is the conversion of a chemical compound into a more toxic form in living organisms or in substrates such as soil or water. The conversion can be caused by enzymatic metabolism in the organisms, as we ...

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;

human Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, cultu ...

s, 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 The European Food Safety Authority (EFSA) is the agency of the European Union (EU) that provides independent scientific advice and communicates on existing and emerging risks associated with the food chain. EFSA was established in February 2002, ...

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 of the eyes and skin. Other subjects with hay fever reported more significant effects, including throat irritation, upset stomach, and difficulty sleeping.

''Trichogramma'' wasps

Trichogramma ''Trichogramma'' is a genus of minute polyphagous wasps that are endoparasitoids of insect eggs. ''Trichogramma'' is one of around 80 genera from the family Trichogrammatidae, with over 200 species worldwide.Consoli FL, Parra JRP, Zucchi RA (201 ...

'' is a genus of

parasitoid wasp Parasitoid wasps are a large group of hymenopteran superfamilies, with all but the wood wasps (Orussoidea) being in the wasp-waisted Apocrita. As parasitoids, they lay their eggs on or in the bodies of other arthropods, sooner or later causin ...

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