Abstract
A major challenge to the area-wide management of Drosophila suzukii is understanding the fly’s host use and temporal dynamics, which may dictate local movement patterns. We determined D. suzukii’s seasonal host use in California’s San Joaquin Valley by sampling common crop and non-crop fruits in a temporal sequence of fruit ripening. We then evaluated the suitability of selected fruits as hosts. Drosophila suzukii emerged from both intact and damaged cherries during the cooler, early season period. Fly density remained low through the hot spring–summer period and re-surged as temperatures lowered in fall when the fly did not cause damage to intact peach, nectarine, plum, pear, grape, pomegranate, apple, persimmon and citrus (in order of ripening) but did emerge from the damaged fruits of these crops. The fly also emerged from two ornamental fruits (loquats and cactus) but was not found on wild plum and two endemic wild fruits (buckthorn and bitter berry). Drosophila suzukii completed development (egg to adult) on cactus, mandarin carpel, pomegranate seed, wild plum and buckthorn at survival rates similar to cherry (51.2–68.8%), whereas it had a lower survival rate on bitter cherry (33.2%), table grape (31.5%), raisin grape (26.5%), and wine grape (4.5%). The high acidity levels of grapes negatively affected the fly’s fitness. Among 10 cherry cultivars, survival rate was not affected by sugar content, but it decreased with increasing egg density per gram of fruit. Results suggest that in California’s San Joaquin Valley, the early season crops are most vulnerable, summer fruits ripen during a period of low pest pressure, and late season fruits, when damaged, serve to sustain D. suzukii’s populations in this region.
Highlights
Native to East Asia, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) has been a major invasive pest of soft-and thin-skinned fruits since it was first detected in 2008 in North America and Europe [1,2,3] and has been found recently in South America [4,5]
This study aimed to illustrate the temporal dynamics of host use by D. suzukii in California’s San Joaquin Valley, one of the world’s major fruit growing regions
Cherries were most seriously infested by D. suzukii; for example, a mean of 1.2 ± 0.2 D. suzukii emerged per fruit (n = 723) during May and June in 2013, with a peak infestation on 25 May as high as 2.0 ± 0.2 flies per fruit (n = 50)
Summary
Native to East Asia, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) has been a major invasive pest of soft-and thin-skinned fruits since it was first detected in 2008 in North America and Europe [1,2,3] and has been found recently in South America [4,5]. Landscape composition surrounding cultivated crops, such as forests and shrub vegetation, could act as sinks, sources, shelters or overwinter sites for the fly populations [34,35] For this reason, the availability of alternative hosts could play an important role in sustaining fly populations and dictating their local movement patterns when favorable hosts are not available. The seasonal periods of host utilization and the importance of non-crop hosts within the agricultural landscape need to be understood to develop area-wide programs. In this framework, this study aimed to illustrate the temporal dynamics of host use by D. suzukii in California’s San Joaquin Valley, one of the world’s major fruit growing regions
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