Commercial fields of processing tomatoes located in the Sacramento Valley of California were monitored for eggs of the tomato fruitworm,Helicoverpa zea(Boddie), over a 5-yr period. In general, egg density remained low until near mid-August. During a narrow window of time, egg density increased rapidly across all fields. The first treatable levels ofH. zeaeggs were recorded during this period, or later, for all years. These results better define when to begin sampling processing tomatoes for eggs ofH. zea. Eggs ofH. zeawere found to have an aggregated spatial pattern in tomato fields. A dynamic sequential sampling plan was developed which adjusts the economic threshold according to the level of egg parasitism. When compared with the currently recommended sampling plan, sequential sampling required approximately 60% fewer leaves to reach a management decision.