Various lepidopteran insects are responsible for major crop losses worldwide. Although crop plant varieties developed to express Bacillus thuringiensis (Bt) proteins are effective at controlling damage from key lepidopteran pests, some insect populations have evolved to be insensitive to certain Bt proteins. Here, we report the discovery of a family of homologous proteins, two of which we have designated IPD083Aa and IPD083Cb, which are from Adiantum spp. Both proteins share no known peptide domains, sequence motifs, or signatures with other proteins. Transgenic soybean or corn plants expressing either IPD083Aa or IPD083Cb, respectively, show protection from feeding damage by several key pests under field conditions. The results from comparative studies with major Bt proteins currently deployed in transgenic crops indicate that the IPD083 proteins function by binding to different target sites. These results indicate that IPD083Aa and IPD083Cb can serve as alternatives to traditional Bt-based insect control traits with potential to counter insect resistance to Bt proteins.

The efficacy and non-target arthropod effects of transgenic DAS-21023-5 × DAS-24236-5 × SYN-IR102-7 Bt cotton, expressing proteins Cry1Ac, Cry1F and Vip3Aa19, was examined through field trials in Brazil. Fifteen field efficacy experiments were conducted from 2014 through the 2020 growing season across six different states in Brazil to evaluate performance against key lepidopteran pests through artificial infestations of Chrysodeixis includens (Walker), Spodoptera frugiperda (J.E. Smith,1797), Spodoptera cosmioides (Walker, 1858) and Chloridea virescens (F., 1781), and natural infestations of Alabama argillacea (Hübner) and S. frugiperda. The impact of this Bt cotton technology on the non-target arthropod community in Brazilian cotton production systems was also assessed in a multi-site experiment. DAS-21023-5 × DAS-24236-5 × SYN-IR102-7 cotton significantly reduced the feeding damage caused by S. frugiperda, S. cosmioides, C. includens, C. virescens and A. argillacea, causing high levels of mortality (greater than 99%) to all target lepidopteran pests evaluated during vegetative and/or reproductive stages of crop development. Non-target arthropod community-level analyses confirmed no unintended effects on the arthropod groups monitored. These results demonstrate the value of transgenic Bt cotton containing event DAS-21023-5 × DAS-24236-5 × SYN-IR102-7 for consideration as part of an integrated approach for managing key lepidopteran pests in Brazilian cotton production systems.

Chrysodeixis includens (Walker, 1858) and Rachiplusia nu (Guenée, 1852) are important defoliating pests belonging to the Plusiinae subfamily in the Western hemisphere. C. includens is a major lepidopteran pest of soybean in the Americas, whereas, until 2021, R. nu was more restricted to the temperate regions of South America. Recently, reports of R. nu feeding on Cry1Ac soybean and occurring in tropical regions of Brazil have raised questions regarding the distribution of this species. The morphological similarity of the larvae from the two species makes it difficult to correctly identify the species in the field, which may lead to an underestimation of R. nu in Brazilian territory. This study aimed to address these questions by using a molecular approach to identify Plusiinae caterpillars throughout three seasons in non-Bt, Cry1Ac, and Cry1Ac × Cry1F soybean fields. Here, we carried out a comprehensive spatial sampling of the primary soybean-producing regions in Brazil. The results showed that R. nu has been the main Plusiinae occurring in soybean over the last three years, and it was present in all sampled regions. For Cry1Ac and Cry1Ac × Cry1F soybeans, up to 99% of the samples collected in 2023/24 were identified as R. nu. Non-Bt soybeans had higher variations in the proportion of the two species among the regions and across seasons, indicating that populations of C. includens and R. nu are co-occurring throughout the country. This is, to our knowledge, the most robust report assessing the distribution of C. includens and R. nu in Brazil using a molecular tool. This study provides clarification of R. nu occurrence and highlights the importance of pest monitoring from an integrated pest management perspective.

The genetically modified cotton DAS-21023-5 × DAS-24236-5 × SYN-IR102-7 expressing Cry1Ac, Cry1F and Vip3Aa19 from Bacillus thuringiensis Berliner (Bt) has been cultivated in Brazil since the 2020/2021 season. Here, we assessed the performance of DAS-21023-5 × DAS-24236-5 × SYN-IR102-7 cotton expressing Cry1Ac, Cry1F and Vip3Aa19 against Helicoverpa armigera (Hübner), Helicoverpa zea (Boddie), and their hybrid progeny. We also carried out evaluations with DAS-21023-5 × DAS-24236-5 cotton containing Cry1Ac and Cry1F. In leaf-disk bioassays, DAS-21023-5 × DAS-24236-5 × SYN-IR102-7 was effective in controlling neonates from laboratory colonies of H. armigera, H. zea and the hybrid progeny (71.9%–100% mortality). On floral bud bioassays using L2 larvae, H. zea presented complete mortality, whereas H. armigera and the hybrid progeny showed <55% mortality. On DAS-21023-5 × DAS-24236-5 cotton, the mortality of H. armigera on leaf-disk and floral buds ranged from 60% to 73%, whereas mortality of hybrids was <46%. This Bt cotton caused complete mortality of H. zea larvae from a laboratory colony in the early growth stages, but mortalities were <55% on advanced growth stages and on floral buds. In field studies conducted from 2014 to 2019, DAS-21023-5 × DAS-24236-5 × SYN-IR102-7 cotton was also effective at protecting plants against H. armigera. In contrast, a population of H. zea collected in western Bahia in 2021/2022 on Bt cotton expressing Cry1 and Vip3Aa proteins, showed 63% mortality after 30 d, with insects developing into fifth and sixth instars, on DAS-21023-5 × DAS-24236-5 × SYN-IR102-7 cotton. We conclude that H. armigera, H. zea, and their hybrid progeny can be managed with DAS-21023-5 × DAS-24236-5 × SYN-IR102-7 cotton; however we found the first evidence in Brazil of a significant reduction in the susceptibility to DAS-21023-5 × DAS-24236-5 × SYN-IR102-7 cotton of a population of H. zea collected from Bt cotton in Bahia in 2021/2022.

Chrysodeixis includens and Rachiplusia nu are two species belonging to the Plusiinae subfamily within the Noctuidae family. Due to their morphological similarity, the identification of their larvae is difficult and time-consuming. A rapid and accurate identification of these two species is essential for their management as these species exhibit differential susceptibilities to insecticides and crops engineered to express Bacillus thuringiensis (Bt) proteins, and a molecular tool can easily provide this differentiation. Currently, molecular analysis can identify these species through genetic sequencing, an expensive and time-consuming process. In our study, after sequencing part of the mtDNA cytochrome c oxidase I (COI) gene and based on the differences found in the gene of each species, a set of species-specific primers was developed: one reverse primer common to both species and two forward primers, specific to each species, amplifying fragments of 199 base pairs (bp) for C. includens and 299 bp for R. nu. Our results indicate that the primers were specific for these species, enabling the identification of individuals directly through agarose gel. The new methodology proved to be accurate, rapid, and reliable for the correct identification of these two species of loopers.