USING BAIT TO SUPPRESS THE SOUTHERN FIRE ANT ON AN ECOLOGICALLY SENSITIVE SITE (HYMENOPTERA, FORMICIDAE)

The southern fire ant, Solenopsis xyloni (McCook), attacks the ground nesting, endangered California least tern, Sterna antillarum browni (M earns). Baiting with selected baits suppressed ant populations, reduce d S. xyloni attacks, and was positively correlated with increased St. a. browni fledging success. Granular bait containing 0.9 % (wt/wt) hyd ramethylnon (Max Force) suppressed ant colonies up to 6 mo. Even thoug h the numbers of foraging ants were reduced, some colonies persisted. This suggests selective distribution or differential sensitivity to th e active ingredient within ant colonies. Area-wide baiting reduced los s of tern eggs and chicks attributed to S. xyloni 40.4% within 4 yr. S trategic baiting around bird nests reduced predaceous ants but was not as effective as area-wide + strategic baiting. Tern hatch success, ch ick survival, and percent fledging improved as the number of S. xyloni was reduced.