Caterpillar resistance to Bt soybeans worries MS producers

In Mato Grosso do Sul, rural producers are concerned about the occurrence of the false caterpillar (Rachiplusia nu) in Bt soybeans, mainly the first generation in Brazil (Intacta RR2 Pro). According to researcher Crébio José Ávila, from Embrapa Agropecuária Oeste, the historical occurrence of this species is more common in the states of the southern region of Brazil and Argentina.

However, from the 2019/2020 harvest onwards, caterpillars Rachiplusia nu They have been found more frequently in other regions, such as in the north of Paraná, São Paulo, Minas Gerais, Goiás and Mato Grosso, both in conventional soybean cultivars and in first generation Bt soybeans.

“This fact has led to the suspicion that the caterpillars of R. naked are already resistant to this technology, that is, the process of evolving resistance to this pest is already occurring in the field”, analyzes Ávila. However, according to the researcher, the incidence of these caterpillars in soybean crops has been small, not causing levels of defoliation that justify control.

The researcher emphasizes that one of the necessary requirements to prevent or delay the resistance of these pests to Bt cultivars is the use of a structured refuge in 20% of the area cultivated with soybeans. “This is the main tool of Insect Resistance Management (MRI) to manage caterpillar resistance in Bt soybeans and extend the useful life of this technology”, says Ávila.

Questions about resistance involving Bt soybeans were addressed in several articles and articles in Cultivar Magazine. For example:

• Integrated management of the caterpillar in soybeans;

• Helicoverpa zea attacks soybean crop INTACTA 2 XTEND;

• Caterpillars in BT soybeans;

• Helicoverpa outbreaks put pressure on Intacta crops at the beginning of the 2022-23 harvest;

• Pest pressure in soybean crops;

• ​Advanced management;

• Caterpillars that resist.