Treatment of soybean with methyl parathion and methomyl caused resurgence of populations ofPlathypena scabraF.,Heliothisspp.,Pseudoplusia includens(Walker),Anticarsia gemmatalisHübner, andEpilachna varivestisMulsant. Less resurgence occurred when monocrotophos was applied. Removal of the natural biotic agents by the insecticides was probably the major reason for the resurgence. Newly-established soybean fields in isolated situations were more susceptible to outbreaks of these pests than fields which were cultivated annually.