Banks grass mite (BGM),Oligonychus pratensis(Banks), density was monitored on corn plants of various growth stages that were differentially irrigated. Treatments were designed to create different levels of plant stress by combining factors associated with leaf senescence with stress due to moisture deficits. Plants that showed severe stress symptoms and those without stress symptoms became infested with low BGM numbers. Plants with intermediate stress levels became infested with the most BGM. Plant-canopy temperature measurements indicated that higher temperatures were associated with more mature, water-stressed plants, and canopy temperatures were significantly correlated with BGM numbers. The combined effect of adequate host quality and high microenvironmental temperatures may account for rapid BGM density increases during plant stress episodes.