The red imported fire ant (Solenopsis invicta) is usually considered a serious pest because of its painful sting and the high density of its mounds. Fire ants however, may be beneficial predators in agroecosystems. Recent studies in a variety of crop and orchard systems have shown that fire ants consume significant numbers of economically important pests. These studies also suggest that fire ants are serious intraguild predators that consume large numbers of beneficial arthropods. This study examined the direct effect (predation of caterpillars) and indirect effects (interference with parasitoids) of red imported fire ants on the Diamondback moth (Plutella xylostella) and its larval parasitoids Cotesia plutellae, and Diadegma insulare in collards. Caterpillar and parasitoid densities were both negatively correlated with fire ant density in the field. Percent parasitism was negatively correlated with ant density. Comparisons between a collard monocrop and an intercrop of collards and white clover were also made. Caterpillar densities were significantly lower in the intercrop than in the monocrop. Parasitism rate did not differ between the two cropping systems. Beneficial insect populations, including parasitoids, were much higher in the intercrop. This study suggests fire ants can have complex effects in agroecosystems because they consume both herbivores and beneficial arthropods. Future studies will determine if there is an optimum ratio of fire ants and parasitoids that maximizes biocontrol, or if biocontrol is maximized at extremely high fire ant densities, when intraguild predation is at its highest
Species 1: Hymenoptera Formicidae Solenopsis invicta (red imported fire ant, fire ants)
Species 2: Lepidoptera Plutellidae Plutella xylostella (diamondback moth)
Species 3: Hymenoptera Braconidae Cotesia plutellae
Keywords: intraguild predation, biological control
The ESA 2001 Annual Meeting - 2001: An Entomological Odyssey of ESA