Field Biology of Mexican Corn Rootworm, Diabrotica virgifera zeae (Coleoptera: Chrysomelidae), in Central Mexico

Before the rainy season, eggs of Diabrotica virgifera zeae Krysan and Smith were found to be dormant in nonirrigated fields in Jalisco, Mexico. At this time, soil moisture was about 11.5%. Embryo development began in June, when the soil moisture was about 20%. Initial egg hatch occurred during the first week of July. There appeared to be no difference in the rate of development between D. v. zeae in central Mexico and D. v. virgifera leConte in the U.S. corn belt, but all events in the development of D. v. zeae in nonirrigated fields occurred ca. 1 month later than the same events in the development of D. v. virgifera in the corn belt. The population of D. v. zeae appeared to be adapted to several different cropping practices: in May, before the rainy season began, we found eggs in diapause, larvae, or adults in different fields depending upon the availability of soil moisture and the time of planting. Diseasesand predatorsappearedto have a greater influenceon the populationdynamics of D. virgifera in Mexico than in the corn belt.