Drosophila suzukii Matsumara, also referred to as the spotted wing drosophila, has recently expanded its global range with significant consequences for its primary host crops: blueberries, blackberries, raspberries, cherries, and strawberries. D. suzukii populations can increase quickly, and their infestation is difficult to predict and prevent. The development of effective tools to detect D. suzukii presence in new areas, to time the beginning of activity within a crop, to track seasonal activity patterns, and to gauge the effectiveness of management efforts has been a key research goal. We compared the efficiency, selectivity, and relationship to fruit infestation of a range of commonly used homemade baits and a synthetic formulated lure across a wide range of environments in 10 locations throughout the United States. Several homemade baits were more efficient than apple cider vinegar, a commonly used standard, and a commercially formulated lure was, in some configurations and environments, comparable with the most effective homemade attractant as well as potentially more selective. All alternative attractants also captured flies between 1 and 2 wk earlier than apple cider vinegar, and detected the presence of D. suzukii prior to the development of fruit infestation. Over half the Drosophila spp. flies captured in traps baited with any of the attractants were not D. suzukii, which may complicate their adoption by nonexpert users. The alternative D. suzukii attractants tested are improvement on apple cider vinegar and may be useful in the development of future synthetic lures.

Drosophila suzukii (Matsumura; Diptera: Drosophilidae) is an invasive vinegar fly and pest of soft fruits in North America, including wild blueberries (Vaccinium angustifolium Aiton) in Maine. Despite its presence in the continental United States for 9 yr, little is known about its natural enemy complex. Here we report the results of a 3-yr study designed to identify naturally-occurring predators in Maine's wild blueberry fields. Experiments were conducted to determine pupation site and pupation depth to understand D. suzukii's predation vulnerability. Predation rates in the field of fully-exposed, caged, and buried pupae were measured. Pitfall traps were deployed to identify the potential predator assemblage, and laboratory experiments were conducted to determine how many pupae were consumed by commonly occurring ground beetle species (Carabidae) and field crickets (Gryllus pennsylvanicus Burmeister). The most commonly collected predators were ants, ground beetles, harvestmen, and field crickets. Significantly more pupae were found to occur in the soil compared to blueberry fruit, with most pupae in the top 0.5 cm layer of soil. Pupal predation rates in the field were high, with higher rates of predation on exposed pupae compared to buried pupae. Laboratory studies revealed that ground beetles and field crickets are likely predators of D. suzukii pupae.

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A long-term investigation of D. suzukii dynamics in wild blueberry fields from 2012–2018 demonstrates relative abundance is either still increasing or exhibiting periodicity seven years after the initial invasion. Relative abundance is determined by physiological date of first detection and air temperatures the previous winter. Date of first detection of flies does not determine date of fruit infestation. The level of fruit infestation is determined by year, fly pressure, and insecticide application frequency. Frequency of insecticide application is determined by production system. Non-crop wild fruit and predation influences fly pressure; increased wild fruit abundance results in increased fly pressure. Increased predation rate reduces fly pressure, but only at high abundance of flies, or when high levels of wild fruit are present along field edges. Male sex ratio might be declining over the seven years. Action thresholds were developed from samples of 92 fields from 2012–2017 that related cumulative adult male trap capture to the following week likelihood of fruit infestation. A two-parameter gamma density function describing this probability was used to develop a risk-based gradient action threshold system. The action thresholds were validated from 2016–2018 in 35 fields and were shown to work well in two of three years (2016 and 2017).