Technique to Screen Peanuts for Resistance to the Tobacco Armyworm, Spodoptera litura (Lepidoptera: Noctuidae) Under No-Choice Cage Conditions

Peanut is an important oilseed crop in the semi-arid tropics. It is damaged by several insect species, of which tobacco armyworm, Spodoptera litura F., is one of the most damaging pests in South and Southeast Asia. Because of uncertainty of S. litura infestations under field conditions, we standardized a no-choice cage technique to screen germplasm and breeding material for resistance to this insect. The test plants were infested with different densities of first- and third-instar larvae at 15 d after seedling emergence. Maximum differences in leaf damage rating and percentage loss in plant biomass at 7 d after infestation between JL 24 and ICGV 86031 were observed when the plants were infested with 10 first-instar larvae per plant. When the plants were infested with third-instar larvae, damage evaluation at 48 hr after infestation showed the maximum differences between JL 24 and ICGV 86031. Larval weight was significantly lower on ICGV 86031 as compared to JL 24 at 10,15, and 20 larvae per plant. At 10 larvae per plant, ICGV 86031, GP-NC 343, and TMV 2 suffered less damage than JL 24. Larval weights in general were lower on FDRS 10 (except at 20 larvae per plant) and ICGV 86031 than on JL 24. Leaf damage rating was significantly and positively correlated with larval weight and loss in plant biomass. Fifteen-d-old peanut seedlings infested with 10 first- or third-instar larvae can be used to evaluate peanut germplasm and segregating breeding material for resistance to leaf defoliators such as S. litura