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ARS Home » Southeast Area » Tifton, Georgia » Crop Protection and Management Research » Research » Publications at this Location » Publication #79151
Title: DEVELOPMENT AND BEHAVIOR OF SPODOPTERA EXIGUA (LEPIDOPTERA: NOCTUIDAE) LARVAE IN CHOICE TESTS WITH FOOD SUBSTRATES CONTAINING TOXINS OF BACILLUS THURINGIENSIS

Author
item STAPEL, J. - UNIVERSITY OF GEORGIA
item WATERS, D. - UNIVERSITY OF GEORGIA
item RUBERSON, J. - UNIVERSITY OF GEORGIA
item Lewis, Wallace

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/27/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Plant feeding insects are costly pests of agricultural crops. Resistance and residue problems with conventional pesticides have caused scientists to seek better ways to control pest insects and to delay their resistance to biological control agents. ARS scientists in Tifton, GA and their University of Georgia colleaques are seeking to better understand factors that influence resistance to Bacillus thuringiensis (Bt). This study shows that not only physiological resistance, but also behavioral avoidance by beet armyworm caterpillars may contribute to the decreasing effectiveness of Bt-formulations in the field. These caterpillars are able to avoid feeding on Bt-treated artificial diets and cotton leaves and move to untreated diets when available. This information has important implications for the effectiveness of Bt in biological control programs.

Technical Abstract: The development and behavior of beet armyworm larvae, and their pupal weight were investigated in dual choice tests with artificial diet and cotton leaves containing Bt toxins. In both diet and leaf choice tests with Bt formulation MVP, the proportion of larvae on Bt-free diets was higher than on Bt-containing diet. Artificial diet tests further showed that larvae were more often found on diets where MVP was applied on the diet surface rather than on diet where MVP was mixed in the diet. In leaf tests with the Bt-cotton line C 1076 and the non-Bt C 312, more larvae were found on non-Bt leaves. In the MVP and C 1076 leaf tests, feeding damage also occurred more on Bt free than on Bt-treated leaves. Leaf choice tests with Dipel ES and Xentari and the Bt line C 531 showed different patterns of larval behavior and feeding damage. Survival of larvae was comparable in MVP-choice tests and controls. However, lower pupal weight and longer development were observed. Experiments with neonate S. exigua on MVP treated cotton plants showed that the number of remaining larvae was negatively correlated with Bt concentration and exposure time. The consequences and opportunities for behavior adaptation to Bt in pest management are discussed.