- Drosophila suzukii (Diptera: Drosophilidae), is a serious pest in soft and stone fruit industries worldwide. The unique serrated ovipositor of female Drosophila suzukii allowed the species to reproduce in intact, ripening fruit before the harvest. Current control methods rely heavily on insecticide application, only becoming less profitable due to the high cost of insecticide, labor, and increase in pest pressure. To manage the damage caused by the pest, multiple control methods are being utilized and developed.
Research was conducted to understand the overwintering behavior and possible alternative nutrient sources available for the flies in winter. Distribution of the flies was monitored for two consecutive years in a blueberry farm located in Salem, OR, by using traps containing sugar and yeast water. Active traps were placed in two locations, canopy and ground, within the crop and wild vegetation. Soil and organic material samples were collected from the two environments to analyze for possible simple saccharides. The data and analysis suggest that D. suzukii distribution was affected by temperature. Higher temperature resulted in higher number of fly counts in crop canopy whereas low temperature resulted in higher flies in ground
traps. Passive traps collected a higher number of flies in colder periods. The soil samples and organic materials consistently contained simple saccharides throughout the year in collections from surrounding vegetation, suggesting the decomposition of organic materials could leach simple saccharides to soil, thereby providing important nutrients to D. suzukii during winter bottleneck periods.
The mechanism of aggregation of D. suzukii was investigated through observing conspecific attraction between flies. Research on conspecific attraction of D. suzukii was conducted in ventilated behavioral arenas where each sex was exposed to conspecifics of the same or opposite sex within the arenas. For no-choice assays, each arena contained either a control or a treatment cup trap containing 50 D. suzukii of a sex at a time. In stimuli and no-stimuli choice assays, each arena contained a control (no flies) and a treatment. Sex choice assays were conducted to directly compare male and female D. suzukii attractancy towards a single sex of flies. Attraction of different body sections of female flies were used as an attractancy source to females. In no-choice assays, females were attracted to both males and females. Males were however not attracted to males. From the stimuli and no-stimuli assays, there was no significant difference of attraction between males and females on female flies, but males were attracted to females at a higher rate than to males. There were no significant differences among the treatments for the different body sections but showed a numerically higher attraction between control and abdomen. Increased rates of male aggregation resulted in increased female attractancy.
The effects of abiotic components, temperature and photoperiod, were studied with a focus on pupation behavior of D. suzukii larvae. The number of larvae pupating in, on, and out of blueberries under 5 temperatures (14, 18, 22, 25, and 26) and 4 photoperiods (8;16, 10:14, 12:12, and 14:10 L:D) were measured. The temperature did not affect the location of pupation but photoperiod had a significant impact on the location. With shorter the daylength, more larvae pupated out of the host. Temperature affected the development duration of D. suzukii whereas photoperiod did not. Developmental period was longer under colder temperature regimes. The survival rate from egg to adult was not affected by photoperiod but by temperature.
The results from this research on D. suzukii biology and ecology can be incorporated into management methods. Overwintering behavior of D. suzukii can be incorporated in optimizing the timing of mass trapping in winter. The pupation behavior dependent on photoperiod can contribute towards manipulating the behavior of larvae under field condition to maximize larval mortality. The results from the observations of conspecific attraction behavior can be used as a guide to improvements on current lures for trapping D. suzukii.