Spatial distribution of spotted-wing drosophila (Diptera: Drosophilidae) and other insects in fruit of a sweet cherry (Rosaceae) orchard.
Spotted-wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), is an invasive pest of many small and soft fruits. We present the first results concerning its oviposition in the canopy of a sweet cherry (Prunus avium Linnaeus; Rosaceae) orchard. We examined the distribution of arthropods emerging from fruits of five cultivars ripening successively over seven weeks, in interior and border rows, within four regions of the tree canopy (top/bottom height × north/south aspect), and measured the associated fruit ripeness (°Brix). Single fruits were reared for more than two weeks: 1328 arthropods emerged from 887 cherries in June, and 10 426 emerged from 1071 cherries in July. When populations were low, significantly more D. suzukii were present in the northernmost row and northern canopy aspect. Later, its distribution with respect to cherry row, height, and aspect was homogenous. Drosophila suzukii density per sweet cherry was highest in the latest ripening cultivar, when its distribution was not homogeneous; significantly more D. suzukii were in the centre than the southernmost row, in the lower canopy, and the southern aspect, than elsewhere. In the early season, single egg clutches were found without aggregation. As population density increased, so did intraspecific aggregation, but D. suzukii did not co-exist with other Drosophila Fallén species, nor with Rhagoletis indifferens Curran (Diptera: Tephritidae) when present.