2012 Annual Report
1a.Objectives (from AD-416):
1. Identify wild and ornamental hosts of spotted wing Drosophila (SWD) that serve as population reservoirs for infesting crop fields.
2. Test the effectiveness of predators for biological control of SWD.
3. Test the effectiveness of entomopathogenic nematodes for biological control of SWD.
1b.Approach (from AD-416):
Wild and ornamental fruit will be picked weekly from residential areas, roadsides, growers’ fields in the Mid-Willamette Valley. A subset will be exposed to SWD in 5 replicated lab cages under no-choice conditions to determine if SWD lays eggs and successfully develops on various fruits. SWD-infested potted fruit plants will be placed outdoors in sets of five and spaced at least 50 m apart among a larger agricultural field. Orius will be released at a zero (control), medium and high rate within potted plant sites, with ten replicate sites per treatment. After one week, the infested fruit will be dissected and reared out to determine survivorship of SWD. SWD larvae and pupae (loose within dirt or within fruit) will be exposed to nematodes to determine infection rates.
The invasive spotted wing drosophila (SWD) has attacked numerous small fruit crops in 2009-10 and led to crop loss. While increased insecticide application has reduced infestation levels in crops, outlying areas with non-commercial fruits serve as a constant reservoir of SWD. Knowledge about alternative fruits that may harbor SWD comes mainly from Japan during studies in the 1930s. Also, management primarily relies on chemical applications, and little is known about biological control of the fly.
Wild and ornamental fruit in residential and near crop fields were observed for ripening and collected for laboratory tests where fruit were exposed to SWD for 24 hours with no other host available. Fruits from gooseberry, Indian strawberry, salal, wild cherry, box huckleberry, cherry laurel, hardy kiwi, lingonberry, redtwig dogwood, Pacific Mountain ash, sarcococca, and snowberry were susceptible to SWD. Other fruits from Chinese and Japanese holly, cotoneaster, heavenly bamboo, grape tomatoes, acuba, rosehips, ginko, and hawthorne were not susceptible or were rarely attacked with limited development. The wild and ornamental hosts now known to be susceptible to SWD will identify critical areas in farm/home landscapes for further management and monitoring.
Various natural enemies have been observed among fruits infested with SWD, and their potential as biocontrol agents were examined in the lab and field cages. The release of minute pirate bugs, Orius insidiosus, into outdoor potted blueberry plants with SWD infestations appeared to reduce the number of surviving SWD by 49%, 17%, 27% and 1% during four trials, but results were not significant. The rove beetle, Atheta coriaria, is a ground dwelling predator, and reduced the number of surviving SWD within infested blueberries in the laboratory. Both predators are commercially available and may provide growers and homeowners with additional control options to suppress SWD populations, including reservoir sites. This research was conducted in support of objective 2B of the parent project.