Spatial distribution of spotted-wing drosophila (Diptera: Drosophilidae) and other insects in fruit of a sweet cherry (Rosaceae) orchard

Citation

Chamberlain, A.C., Lalonde, R., Thistlewood, H.M.A. (2020). Spatial distribution of spotted-wing drosophila (Diptera: Drosophilidae) and other insects in fruit of a sweet cherry (Rosaceae) orchard. The Canadian Entomologist, [online] 152(4), 450-473. http://dx.doi.org/10.4039/tce.2020.41

Plain language summary

Spotted-wing drosophila, Drosophila suzukii, is a vinegar fly, similar to those found in homes and garden around ripe fruits and tomatoes. It recently invaded Canada from Asia and attacks many small and soft fruits. Although in Canada since 2009, there are still important parts of its life that are not known. As it is a very important pest of cherries, we studied where the fly lays eggs within trees in a sweet cherry orchard. We looked into which insects came out of five different kinds of sweet cherries that ripened over seven weeks one summer. The trees were from the most central and edge rows, and we studied four places within each tree (top or bottom cherry bunches and north or south face of the tree). We also measured the ripeness of the cherries from each place (sugar concentration, ºBrix). Single cherries were placed in containers in a warm box and followed for more than two weeks each. We saw that 1,328 insects, spiders, or mites, came out of 887 cherries in June, and 10,426 came out of 1,071 cherries in July. When the Spotted-wing drososphila fly was low in numbers, more of the eggs were laid in the most northern orchard rows and in the part of the tree most to the north. Later, as the fly increased in numbers, the eggs were found more or less evenly across all rows, heights, and faces of the trees. The numbers of eggs laid in each cherry increased as the cherries ripened later in the season, and in the last variety the fly was not found everywhere in the same numbers. More Spotted-wing drosophila were in laid in the centre rows than in southern orchard rows, and in the lower part of the trees, and the southern side of the trees, than elsewhere. In the early season, groups of single eggs were arranged randomly in the trees. As their numbers increased, the eggs became more grouped together. Interestingly, Spotted-wing drosophila was not found in the same cherries with other types of vinegar flies (Drosophila species), and nor was it found in the same cherries as western cherry fruit fly (Rhagoletis indifferens).

Abstract

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.

Publication date

2020-01-01