Formica aerata (Hymenoptera: Formicidae) in California vineyards-the biological framework for a hydrogel-based...

Formica aerata is a common ant found in grape vineyards in California's Central Valley and is widely recognized for disrupting the biological control of mealybugs in exchange for honeydew they produce. Research has shown that sugar-feeding ant species can be managed using liquid baits containing low concentrations of a toxicant that is delivered through bait stations or hydrogels. However, the design and effectiveness of baiting strategies depends on a knowledge of ant biology, which for F. aerata had not been determined. We identified cotton balls saturated with 25% sucrose solution to be an effective monitoring tool for F. aerata and determined that foragers are active year-round when ambient temperatures exceed 9 °C. Ant mounds are located close to the bases of vines, and ant foragers on the ground are most commonly found on the berm and near the trunk. Seasonally, peak foraging activity at sucrose-based baits occurred in March and April once ambient temperatures were adequate for foraging during the day and night, but prior to May when foragers bypassed baits to preferentially feed on insect honeydew in the vine canopy. The implications of this research on the development of an effective hydrogel-based baiting strategy for F. aerata in California vineyards are discussed.