Studies to examine the relationship between Banks grass mite densities and physiological changes of maturing sorghum plants were conducted. Cytoplasmic male-sterile and male-sterile-producing sorghum lines were used to create different levels of leaf nitrogen, phosphorus, and carbohydrates by manipulating seed set. Higher nitrogen and carbohydrate concentrations were present in sterile plants, whereas phosphorous levels were influenced more by sorghum variety. Only soluble sugar concentration was significantly related to mite densities throughout the grain filling period, with carbohydrates having a negative influence on the mites. Spider mite response to nitrogen and phosphorus concentrations were dependent upon plant phenology.