Neotropical Brown Stink Bug Euschistus heros (Fabr., 1798) Attack On Bt-Cotton Bolls Cultivated in Brazilian Savannah

The brown stink bug Euschistus heros (Fabr., 1798) is one of the boll-feeding bugs that would acquire higher relative importance in the Brazilian Bt-cotton production system once it seems to be more adapted to the environmental conditions of the production regions. This work had as objective to evaluate the injury and damage capacity of E. heros adults on bolls of Bt and non-Bt cotton plants cultivated in the Brazilian Savannah conditions (22º11’ S and 54^o56’ W). Bolls of transgenic and non-transgenic cotton with approximately 25 mm of diameter were individually infested with E. heros adults. For each cotton genotype the experimental design adopted was the completely randomized being the treatments constituted by the confinement or not of one adult stink bug with the bolls in a five days period. After the confinement period the internal and external locks bolls injury symptoms were evaluated as well the capsules seed cotton weight. The data were submitted to an analysis of variance with a posterior Student’s t-test for means comparison and to a Pearson’s correlation, with p<0.05. In both genotypes infested bolls the mean numbers of locks with internal punctures, warts and immature and mature lint stains signs were significantly higher as well as the capsules seed cotton weight were significantly lower. The non-Bt and Bt-cotton capsules seed weight were significantly reduced at 24 and 13% respectively. Negative significant correlation was detected between external locks symptoms injury and capsules seed cotton weight both on Bt and non-Bt cotton bolls. Internal signs of punctures and warts presented moderate significant correlation with external punctures signs. These results contribute to stink bugs treatment threshold determination on Bt and non-Bt cotton.