Soil application of Popillia japonica control agents with a new injector

The Japanese beetle, Popillia japonica Newman (Coleoptera: Scarabaeidae), is a major pest of turfgrasses, pastures and hay meadows in the invaded areas of North America and Europe. This study evaluated the efficacy of two biocontrol agents (the fungus Metarhizium anisopliae (Metschn.) Sorokin and the nematode Heterorhabditis bacteriophora Poinar) and the insecticide chlorantraniliprole against P. japonica larvae using a soil seeder modified for soil injection with minimum grass disturbance (“Eco Defender 25”). In 2021, trials were carried out at two hay meadows in the Lombardy region of Italy, using water and undisturbed plots as controls. Both biological agents and the insecticide reduced larval densities at one or the other site, but not at both sites, compared to the control. In the following spring, drone surveys conducted over the hay meadows did not show differences in grass quality between treatments, including the undisturbed plots. Overall, the soil injector demonstrated efficacy under distinct conditions, highlighting the need for further optimization according to soil properties.