Mealybug, Planococcus ficus, reduction through pavement ant, Tetramorium immigrans, management using polyacrylamide hydrogel baits in vineyards

Abstract

The mealybug Planococcus ficus Signoret is an important vineyard pest, causing direct damage from feeding as well as vectoring important viral pathogens. Several species of ants tend P. ficus in California, including the pavement ant, Tetramorium immigrans Santschi. We tested the impact of polyacrylamide hydrogels loaded with a 25% sucrose solution and a variety of individual insecticide active ingredients (abamectin, boric acid, pyriproxyfen, spinosad, and thiamethoxam) on T. immigrans populations in vineyards. Additionally, we measured how a reduction of T. immigrans impacts densities of both P. ficus and its natural enemies. All insecticides tested reduced ant counts to some extent. Thiamethoxam was the most effective insecticide tested in both years. Boric acid was the least effective overall with pyriproxyfen and spinosad causing intermediate reductions in ant counts. In a separate trial, thiamethoxam loaded hydrogels reduced ant counts and significantly reduced P. ficus infested grape clusters, but did not reduce P. ficus vine trunk populations, nor increase parasitism rates. This is the first trial of hydrogel bait used for T. immigrans management and demonstrates the effectiveness of polyacrylamide hydrogels as ant baits and that T. immigrans reduction also lowers P. ficus abundance.