Control of spotted wing drosophila (Drosophila suzukii) in sweet cherry and raspberry using bait sprays

Abstract

Spotted wing drosophila (Drosophila suzukii Matsumura) is a major pest of fruit crops with global significance. Effective control is reliant on uniformly spraying insecticides on all crop foliage. To encourage pest attraction and ingestion of insecticides, phagostimulant baits can be employed in ‘attract and kill’ strategies. In semi-field trials, we compared (1) full-field foliar sprays of two insecticides spinosad and cyantraniliprole, with (2) reduced [40%] and (3) low [4%] rates of the insecticides to control D. suzukii and reduce insecticide residues in fruit in sweet cherry and raspberry. The low rates of the insecticides were also combined with baits, (4) Combi-protec, a proprietary mixture of plant extracts, proteins and sugars and (5) molasses; treatment (6) was an untreated control. In both crops, when combined with baits, low rates of insecticides gave comparable control of D. suzukii in fruits compared with the full-rate sprays in most cases, and D. suzukii was significantly lower in these treatments compared with the untreated controls. Crop spray coverage was eight and thirty times higher in the full-rate applications compared with the bait and low-rate sprays, in raspberry and cherry, respectively. The reduction in applied insecticide was achieved by lower concentrations and volumes and a narrower band spray applied across the middle of the crop canopy. Spinosad and cyantraniliprole residues were detected in cherries taken from trees sprayed with full-rate applications but not in fruit from trees given the low rates of insecticides with bait. This study demonstrates that bait sprays can be effectively employed on crops with complex canopies for D. suzukii control.