FORAGING PREFERENCE OF RED IMPORTED FIRE ANTS (HYMENOPTERA, FORMICIDAE) AMONG 3 SPECIES OF SUMMER COVER CROPS AND THEIR EXTRACTS

Foraging preference of red imported fire ant, Solenopsis invicta Buren, among three species of summer cover crops, sesbania, Sesbania exaltata (Rafinesque-Schmaltz) Cory; hairy indigo, Indigofera hirsuta L.; and cowpea, Vigna unguiculata (L.) Walpers, was evaluated in the greenhouse using choice and no-choice tests. Ants derived a large part of their nutrients from aphid honeydew, and ant workers differed in their response to plant species in the presence or absence of cowpea aphid. Ants preferred cowpea > indigo > sesbania when these plants were infested with cowpea aphids, where ants showed no preference between cowpea and indigo when plants were kept free of cowpea aphids. Sesbania showed almost 100% repellency to ants for 8 d, whether these plants were infested or kept free of aphids. In a pickup bioassay for detecting any discrimination among plants by ants, leaf disks from noninfested leaves of cowpea and hairy indigo were picked up more readily than those from sesbania. Response of ants to extracts differed significantly among plants. Sesbania extract repelled and caused mortality in the red imported fire ant. Ethanol extract of sesbania caused higher ant mortality than the water extract.