MORTALITY OF HELICOVERPA-ZEA (LEPIDOPTERA, NOCTUIDAE) EGGS IN COTTON AS A FUNCTION OF OVIPOSITION SITES, PREDATOR SPECIES, AND DESICCATION

Predation rates of Helicoverpa zea (Boddie) eggs on cotton plants were determined by placing 32P-labeled moth eggs on different types of pla nt structures throughout the vertical strata of cotton plants. There w as a slight trend for predation rates to be greater toward the top of the plants. Egg predation rates were higher on mainstem and fruiting b ranch terminals, and on blooms than on other plant parts. Similar pred ation rates (=75%) were observed on abaxial and adaxial leaf surfaces. Seasonal predation rates averaged 81.7 and 81.4 in 1982 and 1983, res pectively. Rates began high each year (81.8-100%) and slowly decreased toward the end of the growing season when rates ranged from 55 to 80% . Predation by sucking predators ranged from 14.2-37.0%; Orius tristic olor (White), O. insidiosus (Say), Geocoris punctipes (Say), and Pseud atomoscelis seriatus (Reuter) were the most important. Chewing predato rs accounted for 0.8-22.9% of the predation. Solenopsis invicta (Buren ) was observed removing more eggs from plants than any other predator species. Ground based predators added significantly to egg predation. Mortality rates of eggs dislodged to the soil surface were also invest igated. Nearly 90% of eggs placed on the soil surface were predated in <48h. Eggs that escaped predation but that were exposed to high midda y soil temperatures (e.g., 45.5-degrees-C) died of exposure. Larvae sa fely eclosed from eggs placed in shaded locations near the plant bases .