Integrated pest management approaches against Drosophila suzukii

The appearance of Drosophila suzukii in 2009 has strongly affected cherry fruit production. Prior to its invasion, Italian cherry orchards were treated with only two insecticide applications, the first against aphids (Myzus cerasi Sulz.) before flowering and the second against Rhagoletis cerasi, about 20-30 days before harvest. After D. suzukii invasion, an additional two-three pre-harvest (close to harvest) insecticide treatments are required, but the number of insecticide applications can increase to five-eight depending on pest abundance, crop susceptibility and other environmental factors. The intensive use of insecticides poses serious concerns about the presence of residues on fruits exceeding maximum residue limits (MRLs), the development of resistance, and negative impacts on the environment beyond beneficials. To obtain a good and sustainable control of D. suzukii the chemical strategies should be coupled with cultural management the use of nets and parasitoids. To achieve good control of the carpophagus larvae it is essential to monitor, both the adults with trap lured with blends of fruit juices and the oviposition on the ripening fruit, since the percentage of infestation is not related to the number of catches in the food traps. Considering the viability of D. suzukii eggs and larvae, it is lower under dry, warm conditions. Therefore, cool humid microhabitats should be avoided by pruning to open up the canopy to increase airflow in the trees and reduce shading. In addition, the use of mulches by reducing standing water in the orchard can further contribute to the reduction of humidity. Precision irrigation should also be incorporated to reduce pooling of water on the ground. Mass trapping, placing numerous traps around the perimeter outside fruit tree fields, is a suitable and cost-effective method only for cultivations where the pest pressure is considerably low, if necessary insecticides could be applied to the surface of the traps to function as an attract-and-kill strategy. Among the sustainable protection techniques for the control of D. suzukii, the use of insect-proof nets has proved effective, reducing or completely replacing the use of insecticides in some instances, and providing high levels of exclusion of D. suzukii from the crop. During the ripening season, sanitary measures such as removal of dropped, infested and over-ripe fruits is suggested. The collection and treatment of infested fruit through sun exposure, disposal in closed containers, crushing, low temperature treatments, bagging and burying, to destroy D. suzukii eggs and larvae are essential IPM procedures to limit the infestation of healthy fruit. The augmentative release of parasitoids and conservation biocontrol of generalist predators, potentially, could contribute to the integrated management of D. suzukii populations, especially in natural habitats close to commercial crops, however further work on the effectiveness of native parasitoids and generalist predators in Europe and the USA, in the field, is required. In this paper, the integration of different tools for D. suzukii control will be discussed, in order to develop effective, eco-friendly and practical strategies for the management of the pest on cherry.