INFLUENCE OF BACILLUS-THURINGIENSIS-TRANSGENIC AND NECTARILESS COTTONON INSECT POPULATIONS WITH EMPHASIS ON THE TARNISHED PLANT BUG (HETEROPTERA, MIRIDAE)

Comparison of Bacillus thuringiensis transgenic and nectariless cotton s with non-B. thuringiensis commercial varieties >2-yr showed no signi ficant differences in number of beneficials, bollworm [Helicoverpa zea (Boddie)], and tobacco budworm [Heliothis virescens (F.)] eggs, fruit ing sites per plant, and percentage square set. Significantly more tar nished plant bugs, Lygus lineolaris (Palisot de Beauvois), and percent age of crazy cotton were observed in B. thuringiensis 757 (Coker 312 b ackground in 1994) and in Coker 312 variety in 1995 compared with othe r varieties, suggesting no effect of B. thuringiensis gene insertion i n cotton on the number of tarnished plant bugs. Transgenic cotton had significantly fewer bollworms and budworms, cabbage loopers [Trichoplu sia ni (Hubner)], and percentage of damaged squares than the other var ieties, 75% as many beet armyworms [Spodoptera exigua (Hubner)], and h ad no effect on fall armyworm [Spodoptera frugiperda (J. E. Smith)]. T he transgenic character itself did not cause an increase of any insect population, but consultants and producers are encouraged to monitor o ther insect pests, especially boil weevil, Anthonomus grandis grandis Boheman, and tarnished plant bug. These pests may cause economic damag e when fewer or no sprays are used for bollworm and budworm in cotton. Nectariless MD51 had fewer plant bugs than other varieties both years , but also lower yield. These results suggest transgenic cotton is a u seful tool in the management of certain lepidopterous pests.