We compared the responses of dryland and irrigated cotton to damage caused by two spotted spider mites in a field experiment at Narrabri. Mites colonies developed at similar rates in irrigated and dryland crops. Despite the similar intensity of infestation, visual symptoms of mite injury were more marked on irrigated plants than on their dryland counterparts. Lint yield of unstressed controls (irrigated, no mites) was 7.8 bales per ha. Water deficit alone reduced yield by 30%. Mites reduced yield more in irrigated (92%) than in dryland crops (72%). Under our experimental conditions, mechanisms of adjustment to water deficit may have enhanced cotton resistance to mites