Populations of predaceous natural enemies developing on insect-resistant and susceptible tomato in North Carolina

Naturally occurring populations of immature and adult Geocoris punctipes, adult Cobomegilla maculata and immature coccinellids were monitored on field-grown tomato lines susceptible and resistant to Manduca sexta and Helicoverpa zea. Helicoverpa tea and Heliothis virescens eggs and small larvae that serve as prey for these predators also were monitored. More H. zea and H. virescens eggs and small larvae were found on resistant than on susceptible plant lines. However, similar populations of large H. tea and H. virescens larvae were found on resistant and susceptible plants. The number of adult Geocoris punctipes, adult Coleomegilla maculata and immature coccinellids on resistant plants was always as high or higher than the number on susceptible plants. The data demonstrate no incompatibility of host-plant resistance with biological control provided by these predaceous insects, but indicate that the number of G. punctipes and coccinellids required to provide effective biological control may develop too late in the season to be of practical value. Large populations of stilt bugs (Jalysus wickhami, Hemiptera: Berytidae) and spiders were observed to occur earlier in the growing season than either G. punctipes or coccinellids and may be a significant source of mortality for H. tea eggs and small larvae. (C) 1997 Academic Press.