Pupation Behavior and Predation on Drosophila suzukii (Diptera: Drosophilidae) Pupae in Maine Wild Blueberry Fields

Abstract

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.

Potential of the European earwig (Forficula auricularia) as a biocontrol agent of the soft and stone fruit pest Drosophila suzukii

“…Although previous work using DNA extraction techniques revealed that F. auricularia are active in predation of SWD, it is likely that they consume more eggs, larvae and pupa than adults . Additionally, high levels of larval predation have been observed in other earwig species and a variety of different prey insects . Limited levels of SWD adult predation contrasted with significant corresponding reductions in SWD larval and emerged adult densities imply that adult predation accounted for little of the population suppression even though SWD were caged with the earwigs within this assay.…”

“…35 Additionally, high levels of larval predation have been observed in other earwig species and a variety of different prey insects. 28,29,40,41 Limited levels of SWD adult predation contrasted with significant corresponding reductions in SWD larval and emerged adult densities imply that adult predation accounted for little of the population suppression even though SWD were caged with the earwigs within this assay. Hence, F. auricularia may more easily predate immature stages of SWD, which are not capable of flight and so are easier to target.…”

“…Considerable research has been undertaken in this area using a variety of species targeting SWD at larval, pupal and adult life‐stages. However, many studies utilize controlled laboratory conditions, where SWD are fed directly to predators . Although significant predation was observed, these conditions do not accurately represent the complex ecosystem structure of a fruit orchard, where such predators are often ineffective …”

“…However, many studies utilize controlled laboratory conditions, where SWD are fed directly to predators. [28][29][30] Although significant predation was observed, these conditions do not accurately represent the complex ecosystem structure of a fruit orchard, where such predators are often ineffective. 31 The role of earwigs, particularly the European earwig (Forficula auricularia Linnaeus), has largely been neglected when considering the potential of predators as biocontrol agents of SWD.…”

Mulching as a cultural control strategy for Drosophila suzukii in blueberry

“…Drosophila suzukii 3rd instar larvae usually leave the fruit to pupate under the soil, 38,39 which as shown above, increases their chances of survival. Impeding larvae from reaching protection underground may be a valuable strategy to reduce D. suzukii population pressure.…”