synonymBacillus thuringiensis(Bacillus thuringiensis) generally refers to Bacillus thuringiensis (including a class of crystal producing Bacillus of many varieties)
Bacillus thuringiensis (Bt) has been discovered for 100 yearspestIt has played a huge role in prevention and control, and is the most in-depth research, fastest development and most widely used in recent yearsMicrobial insecticide。The insect prevention principle of Bacillus thuringiensis is that its strain can produceendotoxin（Companion crystal）AndExotoxinTwo kinds of toxins, which make the pests stop feeding, and the pests die of hunger, blood destruction and neurotoxicity[1]。
Bacillus thuringiensis in NA medium（Nutrient agarNutrientAgar)colony of bacteriaIt is round or oval, light yellow, with irregular edges,OpaqueSlightly uplifted in wax dripping shape.Under the microscope, the Bacillus thuringiensis cell is in the shape of purple oval rod, with the size of (1.2 ～ 1.8) μ m × (3.0 ～ 5.0) μ mShort chainOr long chain arrangement,SporeIt is oval, grows near the middle, and the spore sac is slightly expanded[1]。
Action mechanism
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Bacillus thuringiensis can be used as low toxic insecticide of microbial origin toGastrotoxic effectMainly.The bacterium can produce two kinds of toxins, namelyendotoxin（Companion crystal）AndExotoxin, so that the pests stop feeding, and finally the pestscell wallDeath due to rupture, blood deterioration and neurotoxicity;However, the exotoxin has a slow effect, which is obvious during molting and metamorphosis. These two periods are RNA synthesisfastigium, exotoxin can inhibitDNAOfRNA polymerase。The drug has a slow effect. It takes about 2 days for pests to take it and lasts for about 1 day. Therefore, it should be used more frequently than conventional medicineChemicals2~3 days in advance, and the effect is better in the early stage of pests.yesfishBees are safe, butsilkwormHigh toxicity.
Bacillus thuringiensis preparation mainly has good control effect on some lepidopteran insect larvae, and can be used to control cabbage caterpillars and rice bracts,Inchworm, pine caterpillar, tobacco budworm, corn borerbollworm, rice leaf rollerCoir moth、GeotigerEtc.The insecticidal principle is that Bacillus thuringiensis parasitizes in the midgut of the host after being ingested by pestsAlkaline environmentThe crystal toxin is hydrolyzed by protease in the intestinal tract of the worm, forming less toxic effectSubunit, they act on the midgut of the wormepithelial cells, causing intestinal paralysis, perforation, insect paralysis, and stop eating.Then Bacillus thuringiensis enteredHemocoelomReproductionsepticemia, leading to insect death[2]。
1. Bacillus thuringiensis can play a full role only when the temperature is high (above 20 ℃), so the application effect is the best from July to September;The suitable period of application is generally better than that of applicationChemical pesticide2-3 days in advance[3]。
2. It is effective for rice leaf roller, corn borer, bridge worm, pine caterpillar and tea caterpillar, but it is effective forBig BorerPoor effect[3]。
3. Low toxicity to bees, butsilkwormandCastor silkwormIt is highly toxic and should be strictly controlled. It cannot be used in areas where silkworms are raised.If mulberry leaves are stainedMushroom powder0.2%bleaching powderSterilization, washing and drying before feeding[3]。
4. Do not mix with bactericide[3]。
5. It should be sealed, shaded, stored in a cool, dry place, and protected from rat bites[3]。
