Water Deficit Enhanced Cotton Resistance to Spider Mite Herbivory

We investigated the responses of cotton (Gossypium hirsutumL.) to the combined effects of soil water deficit and two-spotted spider mite (Tetranychus urticaeKoch) infestation. Two mite treatments (-M: uninfested, +M: artificially infested 83 d after sowing), and two water regimes (+W: well watered, -W: water stressed) were combined factorially in four treatments. Mite colonies developed at similar rates in well-watered and water-stressed crops. Despite the similar intensity of infestation, visual symptoms of mite injury were more marked in well-watered host plants (+M+W) than in their water-stressed counterparts (+M-W). Lint yield of unstressed controls (-M+W) was 175 g m-2. In uninfested crops, water deficit reduced yield by 30%, mites reduced the yield of well-watered crops by 92%, and the combination of mite infestation and water deficit reduced yield by 72% (water effect:P