Embrapa publishes technical note guiding the management of caterpillars in Bt soybeans

Studies carried out by Embrapa Soja have demonstrated that caterpillars Rachiplusia nu e Crocidosema aporema can develop in crops with first generation Bt soybean cultivars (Intacta RR2 Pro, which expresses the insecticidal protein Cry1Ac and helps in the management of some species of caterpillars), indicating resistance at the field level. The results of the study are available at Technical Note, prepared by researchers Adeney de Freitas Bueno and Daniel Ricardo Sosa-Gómez, from Embrapa Soja. Even though the issue of resistance indicates a warning, the researchers state that the identification of resistant populations of the two caterpillars should not impact the performance of Bt-soy technology for the management of other target species. Furthermore, preliminary studies with second-generation Bt soybeans (pyramided technology with the proteins Cry1Ac, Cry1A.105 and Cry2Ab2) reveal that the technology is efficient in controlling caterpillars. Rachiplusia nu  resistant to first generation Bt soybeans. 

According to the researchers, a fundamental aspect to avoid the selection of resistant caterpillar populations in crops with the Intacta RR2 PRO technology is the use of refuge areas. This is a preventive measure that consists of the coexistence of crops with Intacta RR2 PRO technology next to crops not equipped with this technology, at a distance of less than 800 meters.

“In addition to the importance of adopting structured refuge, it is recommended to use insecticides only when the level of pest action is reached in the field”, highlights Bueno. Regarding the level of action, the researcher explains that it is recommended to start control in the presence of more than 20 large caterpillars per meter of soybean row. And with regard to defoliation, the right time to start control is when there is 30% defoliation in the vegetative period or 15% if the crop is in the reproductive stage of development. Insect identification can be aided with the Manual for identifying insects and other invertebrates in soybean crops from Embrapa. 

See the full Technical Note here.