A pre-flower infestation of cotton aphid (Aphis gossypii (Glover)) in cotton significantly reduced total lint yield in this large scale, replicated field study in NE Arkansas. The infestation time extended from squaring node 5 to first flower at which time population numbers crashed due to an endemic entomopathogenic fungus. Treatment plots receiving 2 applications of Provado 1.6F applied at 2 ounces/acre produced a mean yield of 940 lb lint/acre compared to production of 863 lb lint/acre in the untreated check. Although insecticide applications resulted in higher yields, when chemical and application costs were included in the analysis, differences in net profit between protected and unprotected plots were only marginally significant (P=0.08). Crop monitoring information derived using the COTMAN system was used to evaluate crop response to stress, monitor square retention, and examine treatment effects on crop earliness. Stress associated with the timing of aphid infestation was evident in crop development curves generated by COTMAN. Square retention data indicated that other important pests likely were not involved in treatment effects. Earliness measured as days to cutout (when NAWF=5) and counts of open bolls was not affected by treatments.