When agrochemical spray solutions are prepared, unforeseen circumstances can prevent spray solution application, resulting in agrochemical remaining in the spray tank for 1 or more days. Information about the impact of delayed applications on agrochemical performance is limited. Experiments were conducted in 2009 and 2010 to determine the effect of delayed spray applications on efficacy of defoliants, insecticides, and plant growth regulators commonly applied to cotton. Each agrochemical was mixed individually on the day of application and 3, 6, and 9 d prior to application using the same water source, and all applications were made on the same day. Defoliation by ethephon and thidiazuron was affected when products were left in solution for extended periods of time. Efficacy of ethephon, indoxacarb, methomyl, spinosad, and thidiazuron was influenced when spray solution application was delayed, whereas efficacy of acephate, carfentrazone, diuron plus thidiazuron, ethephon plus cyclanalide, indoxacarb, lambda-cyhalothrin, lambda-cyhalothrin plus thiamethoxam, methomyl, thiadiazuron, and thiodicarb was not affected by mixing interval. When changes in efficacy occurred, the magnitude of the effect was relatively minor and most likely would be of little biological significance.