Activity and infestation risk of spotted-wing drosophila (Drosophila suzukii) on Indiana blueberries

Spotted-wing Drosophila (SWD), Drosophila suzukii (Matsumura), is an economically-important pest of small fruits worldwide, and was first detected in Indiana in 2012. Currently, there is limited knowledge of seasonal SWD activity and corresponding risk of infestation for blueberry varieties grown in Indiana. Thus, growers must base their management decisions on information gained from neighboring regions, where environmental conditions and crop phenology may differ, affecting local success of SWD management.

We used the published SWD developmental thresholds of 7.2 °C (lower) and 31.5 °C (upper) and the single-sine method to calculate accumulated degree days starting at May 14^th. To better predict SWD activity and infestation risk in Indiana blueberries, we tracked cumulative degree days and number of SWD adults detected in commercial Scentry traps at two highbush blueberry orchards in North Judson (NJ, 1x/week) and West Lafayette (WL, 2x/week) growing ‘Bluecrop’, ‘Blueray’, and ‘Elliot’ blueberry varieties from May to August 2021. Predictive models for SWD activity at both locations exhibited an S-shaped curve. SWD was first detected at the WL site at 610 CDD on June 25^th, with 25% and 50% of adults detected at ~1113 and ~1286 CDD, respectively. SWD was first detected at the NJ site at 355 CDD on June 11^th, with 25% and 50% of adults detected at ~971 and ~1148 CDD, respectively. Our preliminary models have the potential to help Indiana blueberry growers better predict seasonal SWD activity and thereby improve the timing of management practices against SWD.