Oviposition acceptance and larval development of C hilo partellus stemborers in drought‐stressed wild and cultivated grasses of E ast A frica

Maternal host choices during oviposition by herbivorous insects determine the fitness of their offspring and may be influenced by environmental changes that can alter host‐plant quality. This is of particular relevance to ‘push‐pull’ cropping systems where host preferences are exploited to manage insect pest populations. We tested how drought stress in maize and companion plants that are used in these systems affect oviposition preference, larval feeding, and development of the spotted stemborer, C hilo partellus   S winhoe ( L epidoptera: C rambidae). Five host species were tested (all P oaceae): maize ( Z ea mays   L .), N apier grass ( P ennisetum purpureum   S chumach), signal grass [ B rachiaria brizantha ( A . R ich) S tapf], B rachiaria cv. ‘ M ulato’, and molasses grass [ M elinis minutiflora ( B eauv.)]. Under drought stress, maize experienced as much oviposition as control unstressed maize in choice and no‐choice experiments. Similarly, larval leaf damage was not significantly different in drought‐stressed vs. unstressed maize. In contrast, oviposition occurred less on drought‐stressed than on unstressed N apier and signal grass. Oviposition acceptance and leaf damage remained low in both drought‐stressed and unstressed molasses grass and M ulato. Larval survival and development remained high in drought‐stressed maize, but not in N apier, signal, and molasses grass and M ulato, where survival and development were low in both drought‐stressed and unstressed plants. Our results indicate that herbivore responses to drought‐stressed plants depend on the plant species and that drought stress can change host preference and acceptance rankings. In particular, trap‐crops such as Napier grass may not divert oviposition from the main maize crop under drought stress conditions.