LAUSR

ABSTRACT Several genetically modified maize events expressing insecticidal proteins from Bacillus thuringiensis (Bt ) have been commercially available in Brazil, intended to control of fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae). The objective of this study was to evaluate the efficiency of transgenic ( and conventional (non- Bt ) Bt ) hybrids in the control of fall armyworm, treated or not with insecticides through-out three late growing seasons. To this end, trials were conducted at three locations in the state of Sao Paulo, in a randomized complete block design, in factorial arrangements with 5x4, 5x4 and 8x4 factors, respectively. The first factor consisted of the number of commercial hybrids of different companies. The second factor was represented by the different control managements of insect (non- Bt hybrid with and without insecticide; Bt hybrid with and without insecticide). The damage caused by fall armyworm was evaluated on a visual 1-9 scale, from score 0 (no damage) to 9 (totally destroyed whorl), and grain yield (kg ha