SYSTEMIC INDUCTION OF FEEDING DETERRENTS IN COTTON PLANTS BY FEEDING OF SPODOPTERA SPP LARVAE

Cotton, Gossypium hirsutum L., has been shown to exhibit systemic indu ced resistance to arthropods under certain conditions. We conducted ex periments to determine the effects of previous feeding of Spodoptera e xigua Hubner and Spodoptera littoralis (Boisd.) larvae on feeding beha vior, growth, and survival of larvae subsequently feeding on cotton. I n one feeding choice test, S. exigua larvae preferred young leaves fro m undamaged control plants to undamaged young leaves from a previously damaged plant. Feeding deterrence was noticeable after only 6 hr of i nitial feeding damage by larvae, and there was almost complete deterre nce after 30 and 54 hr of continuous feeding. In a second feeding choi ce test, S. littoralis larvae fed more on mature leaves from undamaged control plants than on undamaged mature leaves from previously damage d plants. In no-choice tests, third instars of S. littoralis fed undam aged young leaves from damaged plants did not gain weight and died by the seventh day, whereas larvae fed young leaves from undamaged contro l plants gained weight and pupated within 11 days. Sixth instars of S. littoralis fed either old damaged leaves, old undamaged leaves, or yo ung undamaged leaves all from previously damaged plants gained weight slowly and took more than 12 days to pupate, whereas larvae fed young leaves from undamaged plants gained weight rapidly and pupated within five days of the beginning of the experiment.