Cry1Ab toxicity against four species of the Diatraea sugarcane borer complex in Colombia

The multiple Diatraea (Lepidoptera: Crambidae) species comprising the stem borer complex are among the most damaging pests of sugarcane in the Americas, with D. saccharalis, D. indigenella, D. busckella, and D. tabernella considered as the most widespread species in Colombia. Entomological research in Colombia has focused on the use of egg and larval parasitoids to control populations and minimize their negative economic impacts. However, the declining effectiveness of these parasitoids on certain species has encouraged the exploration of complementary management strategies, including alternatives such as insecticidal proteins derived from Bacillus thuringiensis (Bt). This study evaluated the toxicity of the Cry1Ab protein from Bt against the four most widespread species of the Diatraea complex in Colombia using a bioassay protocol with fresh corn tissue. The mortality rate of Cry1Ab protein followed a concentration response in three of the four species tested, enabling the estimation of toxicity parameters [Lethal Concentration (LC) LC₅₀ and LC₉₅]. Growth inhibition (GI) and growth index (GInd - RGI) were higher than 90% and lower than 0.1, respectively, for all species tested. These results demonstrate that the toxicity of Cry1Ab is similar in all four Diatraea species tested in this study, supporting the potential use of this Bt protein as an alternative management for these pest species.