Resistance in Vegetative and Reproductive Stages of a Soybean Breeding Line to Three Defoliating Pests (Lepidoptera: Noctuidae)

J. Econ. Entomol. 85(4): 1507-1515 (1992) ABSTRACT Resistance in certain genotypes of soybean, Glycine max (L.) Merr., has been shown to adversely affect insect behavior and development in laboratory feeding experiments involving excised leaf material. This study investigated effects of resistance in various developmental stages of intact soybean plants on feeding behavior and physiology of corn earworm, Helicoverpa zea (Boddie); soybean looper, Pseudoplusia includens Walker; and velvetbean caterpillar, Anticarsia gemmatalis Hiibner. Soybean genotypes 'Cobb' (susceptible) and 'GatIR81-296' (resistant) were grown in the greenhouse and used in choice and no-choice experiments. Choice tests showed the presence of resistance in 'GatIR81-296\ and sequential observations of behavior indicated that the insects were inhibited by constitutive factors and components associated with damaged plants. Nochoice tests indicated that resistance occurred in vegetative and reproductive stages of 'GatIR81-296' and resulted in reduced feeding and number of larvae on plants, smaller larvae and pupae, and slower larval development compared with the insects on 'Cobb'. Resistance in 'GatIR81-296' was attenuated in intact reproductive stage plants (R2-R3) compared with vegetative stage (V3-V4) ones.