Impact of red imported fire ant on foliar herbivores and natural enemies

The impact of red imported fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae), on foliar herbivores was examined in a commercial 'Cheyenne' pecan orchard for two seasons by establishing amethoprene bait treatment, a chlorpyrifos hunk treatment and an untreated control. Ants were monitored by periodic mound counts. Herbivores and their natural enemies were monitored by inspecting foliage and deployment and recovery of corrugated cardboard refuge strips. Methoprene bait treatment significantly reduced red imported fire ant mounds compared to the other treatments. Blackmargined pecan aphid, Monellia caryella (Fitch) (Homoptera: Aphididae), was the primary herbivore present during both seasons, with peak densities occurring in June, but not exceeding economic thresholds. Natural enemies, particularly lacewings, lady beetles and spiders, fluctuated in density in concert with aphids. The red imported fire ant was not shown to affect aphid densities, but lacewing larvae and pupae and lady beetle adults were significantly greater on some sampling dates in treatments where fire ants were reduced. Fire ants may have a limited impact on natural enemies. The pecan IPM program for managing herbivores in the canopy does not require adjustment to accommodate red imported fire ant at this location. Generalization to remaining sites in Texas awaits completion of other studies underway.