SOARES, Misael Mendes.; VASCONCELOS, Eduardo Domingos.; BRAZ, Luana Camilla Cordeiro.; RAMOS, Jean Pierre.; SILVA, Carliane Rebeca Coelho da.; SOFIATTI, Valdinei.; SANTOS, Roseane Cavalcanti dos.
Résumé:
Corn Bt is widely used in crops on Southeast- Mid West belt for control of
several Lepidoptera, among them fall armyworm (Spodoptera frugiperda). This
technology has been adopted worldwide for more than 20 years, however, with
continuous use reports of resistance breakdown have been recorded as a function of
insect selection pressure. Monitoring and pursuing strategies to delay this process
ensure the sustainability of this technology. In order to evaluate the toxicity of Corn Bt
(2B655PW) in a semi-arid environment, mortality of fall armyworm larvae was estimated
using leaves collected in four growth stages. Seeds of Bt and conventional were
cultivated in the field during final of rainy season. Leaves were collected at 40, 55, 70
and 85 days after emergence and used to feeding assays, using larvae in cage (24-well
plates) and subsequently maintained in BOD (25 ± 2 ° C) for 5 days. The rate of mortality
was 100% in larvae fed on 40 dae-leaves. With the course of the crop cycle, there was
a low reduction reaching a value of 92.8% at 85 dae. This indicates that this technology
is promising in controlling S. frugiperda under semi-arid conditions. However,
considering the infestation of insects in extensive areas, it is necessary constant
monitoring in the field in order to detect possible emergence of resistant insects that
could accelerate the fall in efficiency of the cultivar.
