Induced resistance to the common cutworm, Spodoptera litura (Lepidoptera: Noctuidae) in three soybean cultivars

We investigated induced resistance to the common cutworm, Spodoptera litura, in three soybean cultivars, 'Bay', 'Fukuyutaka', and 'Himeshirazu'. Levels of induced resistance caused by S. litura herbivory varied among the cultivars. High induced resistance was found in 'Bay', with less food consumption by larvae (78.2%), less larval weight gain (67.3%), longer larval duration (114.2%), and lighter pupal weight (79.7%) than on uninjured plants (100%). The same trends were observed in larvae feeding on leaves of previously damaged plants of 'Fukuyutaka', which is susceptible to S. litura, but only larval duration was significantly prolonged (107.3%). No apparent effect of previous herbivory on plants was found in 'Himeshirazu', which is constitutively resistant to S. litura. Prior mechanical injury to leaves of 'Bay' also decreased subsequent food consumption by larvae (82.9%), but had little effect on larval growth.