Mesh covers on sentinel parasitoid traps prevent Drosophila suzukii movement and impact parasitism by Ganaspis brasiliensis and Pachycrepoideus vindemiae

Abstract

Parasitoids such as Ganaspis brasiliensis and Pachycrepoideus vindemiae are currently researched for biological control of Drosophila suzukii, an important agricultural pest of small fruits. Parasitoids can be monitored in the field by collecting infested fruit samples. When this is not possible, sentinel traps can assess parasitoid presence. Sentinel traps may be covered with a selective barrier to allow movement of parasitoids and prevent nontarget infestation and developing D. suzukii from exiting. In this study, two types of fabric mesh (square 1.1 x 1.1 and oval 1.2 x 0.8 mm openings) were assessed for passage of D. suzukii, G. brasiliensis, and P. vindemiae, and parasitism rates. In addition, wire meshes (1.04, 1.08, 1.11, 1.13, 1.18, and 1.53 mm2) were tested as a more durable alternative to the fabric mesh for G. brasiliensis sentinel traps. Both fabric meshes and the 1.08 and 1.3 mm2 wire mesh prevented passage of D. suzukii. Passage was similar through fabric oval and square mesh for both parasitoids. For G. brasiliensis, parasitism was 3-fold higher in open control sentinel than square mesh covered sentinels in one trial, but parasitism was similar at ~40% in open and square mesh sentinels in another trial. The 1.04, 1.08 and 1.13 wire mm2 mesh lowered G. brasiliensis parasitism. For P. vindemiae, parasitism was 2-fold higher in oval mesh than open sentinels which may be due to the mesh encouraging this wasp to forage longer. If a selective mesh must be used, the square fabric mesh prevented D. suzukii passage, and resulted in the highest G. brasiliensis parasitism compared to wire meshes.