Bt Research 2025, Vol.16, No.5, 204-213 http://microbescipublisher.com/index.php/bt 206 Combining Bt with predatory natural enemies can complement each other's advantages and improve prevention and control benefits. On the one hand, Bt has a special and efficient toxic effect on Lepidoptera feeding pests, while natural enemies such as ladybugs and suckling pests can continuously suppress piercing and pest species that Bt has not been prevented and controlled. In fields where Bt cotton are planted, although bobworms and other borer pests are effectively controlled by Bt toxic proteins, the population of secondary pests such as aphids may increase. At this time, the rich ladybug and grass flies in the fields can play a role in controlling aphids, keeping the total pest volume at a low level. On the other hand, Bt administration is relatively safe for predatory natural enemies and will not cause direct death or abnormal behavior of natural enemies. Studies have shown that predatory ladybug larvae have not been significantly affected after feeding Bt-infected prey. This means that in the presence of Bt, predatory natural enemies can still perform their harm control function normally (Zhu et al., 2006). Therefore, the simultaneous release or protection of predatory natural enemies in the IPM strategy and the application of Bt preparations can achieve three-dimensional control of different pests. Figure 1 Protein profile and structural features of the parasporal body (PB) of Bacillus thuringiensis subsp. israelensis (Bti) (Adopted from Rudd et al., 2023) Image caption: (A) SDS-PAGE showing the major crystal proteins of the PB, i.e., Cry4Aa1 (135 kDa), Cry4Ba1 (128 kDa), Cry11Aa1 (65 kDa), and Cyt1Aa1 (27 kDa). (B,C) Representative transmission electron micrographs through two Bti parasporal bodies with the arrows pointing to the multilaminar fibrous matrix (MFM) that surrounds each individual crystal protein (white arrowheads indicates MFM inner layer). (D) Black arrowheads point to the tightly packed MFM surrounding the Bti PB after lysis of the cell at the end of sporulation. (E) Purified MFM after the insecticidal proteins have been dissolved in alkaline buffer. (F,G) Negatively stained MFM envelope after dissolution of the insecticidal proteins. Note the hexagonal pattern of the MFM (Adopted from Rudd et al., 2023) 3.2 The synergistic effect of parasitic bees in Bt application system Parasitic natural enemies (parasitic wasps, etc.) develop and reproduce by laying eggs into the body of pests, and ultimately killing the host. They are important natural nemesis of agricultural pests. When used in combination with Bt, parasitic wasps can attack pests at different developmental stages, thus forming a complementary cooperation with Bt. Red-eyed wasps parasitic pest eggs cut off their hatching source; while Bt mainly poisons the hatched larvae, and the two are connected in time, forming a continuous blow (Nascimento et al., 2018). For example, cocoon bees parasitize in the body of Lepidopteran larvae. When Bt is applied at the same time in the field, some larvae that have not been parasitized will be poisoned by Bt. Even if the parasitized larvae develop slowly, they can be consumed and killed by parasitized bees larvae. Bt is sprayed for a period of time after the parasite is released, which not only ensures that the parasite has the opportunity to complete parasitic development,
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