Role of Bt. Gene In Control of Insect Pest With Special Reference to Diamondback Moths |

ABSTRACT:

These studies have documented that Bt-resistant insectscan survive on Bt plants and that different management strategies willinfluence the durability of resistance. Although these studies provided someinsight into variables that could be manipulated to delay the onset of resistance,the present field study was performed to provide further data to help identifyvariables that may influence resistance management in the field. fieldexperiment examined the effect of refuge size and refuge placement (mixed vs.separate refuges) on the distribution of the larvae within the plots as well asthe level of resistance in diamondback moths at the end of the season. Ourresults demonstrated that the cumulative number of larvae per plant on refugeplants through the season in the 20% mixed refuge was significantly lower (6.4vs. 14.6) than the 20% separate refuge (Table 1). This finding indicates that,as in our previous greenhouse experiments, a separate refuge is more effectiveat conserving the number of susceptible alleles because larvae on these refugeplants will be more likely to survive to adults (either SS or RS) that can matewith RR individuals and thereby reduce the number of RR offspring. This findingprovides evidence to support the use of a separate refuge for Bt-transgenic cropsthat are attacked by insects that can move between plants as larvae. On theBt-expressing plants over the season, an average of £0.3 larva was found in anyof the treatments, indicating that the diamondback moth population was beingcontrolled by the Btexpressing plants (Table 1). This was also confirmed by theabsence of any larvae on the Bt-expressing plants at the end of the season