ABSTRACT

The effects of the Red Imported Fire Ant, Solenopsis invicta (Buren) (IFA hereafter), on common predators, cotton aphid populations, and its predation on eggs of bollworm (Helicoverpa zea Boddie) and beet armyworm (Spodoptera exigua Hubner) were evaluated under field conditions in central Texas. Fire ants were excluded from large field plots using selective insecticidal baits while adjacent plots were left untreated. Cotton aphid populations were ca. 5.5 times higher in plots with ants versus plots without ants, but did not reach the economic threshold. Densities of convergent lady beetles were greater in the presence of IFA because they respond to the greater density of cotton aphids, which were tended by IFA. Densities of minute pirate bugs, spiders and lacewing were less in the presence of IFA. Predation of sentinel bollworm eggs, indicated by their absence after 24 h, was two times higher in plots with ants versus plots without ants. Most predation of sentinel beet armyworm egg masses, measured via direct nocturnal observations, was due to IFA (68%) and cotton fleahoppers [Pseudatomoscelis seriatus (Reuter)] (21%) in plots with ants, and by the mite Abrolophus sp. (52%), spiders (13%) and minute pirate bug (Orius sp.) in plots without ants. The results of this study show that while IFA promote aphid populations early in the growing season, fire ants significantly increase the predation of bollworm and beet armyworm eggs by the total predator complex.