The globalization of fruit markets and recent expansion of susceptible fruit production likely resulted in the rapid spread of Drosophila suzukii and contributed to the rise in its economic impact. In 2009, up to 80% of the annual value ($421.5 million) of cherry, blueberry, caneberry and strawberry was estimated as the worst-case scenario loss in western US production regions.
Non-crop plants adjacent to cultivated commercial crops may exacerbate the economic impact of pests being a potential alternative as host source. Nearby "Himalaya" blackberry (HB), Rubus armeniacus and seedling cherry, Prunus spp., habitats may be possible shelter and source of D. suzukii infestation. Movement of D. suzukii from field margins to commercial crops is, however, largely unknown.
US scientists have studied the role of field margins containing HB and their effect on D. suzukii activity, density and distribution in an adjacent commercial red raspberry crop.
The overall goal of the work was to conduct mark–capture studies to determine the activity levels of D. suzukii within non-crop field margins and cultivated raspberry crop fields. The specific objectives were to determine: - whether D. suzukii utilizes HB containing field margins as a refuge, - whether crops adjacent to HB-containing field margins have higher population densities compared to crops near non-host (NH) field margins, - the distribution pattern of D. suzukii in cultivated raspberries adjacent to field margins containing HB in comparison with NH field margins. A 33.4-ha cultivated red raspberry study site with field margins containing either HB (Himalaya blackberry) or NH (non-host) was located near Jefferson, OR.
This study is the first to demonstrate that D. suzukii may utilize nearby habitat containing HB as a refuge and may migrate from this habitat and colonize a nearby crop.
Scientists conclude: "The study illustrates the potential risks associated with one such alternate host occurring in closely adjacent vegetation on pest pressure exerted by D. suzukii to cultivated fruit crops. Overall, the activity of D. suzukii in non-crop host areas may be dependent on plant architecture, age, competition, number of hosts, water availability and seasonal fruit selection. A landscape with a combination of plants that provide D. suzukii with a food source from spring to fall, overwintering refuge and satisfactory environmental conditions could increase potential risks of crop infestation by D. suzukii. Other effects of surrounding vegetation, such as D. suzukii insecticide resistance management, potential as D. suzukii trap crop and alternate resources for pollinators, and possible enhancement of biological control need to be considered when developing management strategies."
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