Location: Horticultural Crops Research2013 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. Documents SCA with Oregon State University.
3. Progress Report:
This research was conducted in support of NP304 objective 2B of the parent project. The invasive spotted wing drosophila (SWD) has attacked numerous small fruit crops 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 collected for laboratory no-choice tests. Fruits that were susceptible were further tested in choice tests with a currently ripening cultivated crop. In choice cages where an equal weight of two hosts were provided more SWD developed on ‘Totem’ strawberry than Indian stawberry. Hardy kiwi, redtwig dogwood, cherry laurel, huckleberry and lingonberry were more susceptible than ‘Pinot noir’ or ‘Pinot gris’ wine grapes. More eggs were laid and subsequently more flies developed in hardy kiwi, cherry laurel, and huckleberry. This indicates that files showed a preference for these hosts as ovipositional substrates. In contrast, a similar proportion of eggs were laid among dogwood and lingonberry, but significantly more developed from these hosts than the wine grapes. In this case, SWD may not prefer either host as ovipositional substrates but experience differential survival on the hosts. The wild and ornamental hosts now known to be susceptible to SWD will pinpoint critical areas in farm/home landscapes for further management and monitoring. Natural enemies have been observed among fruits infested with SWD, and their potential as biocontrol agents were examined in the laboratory studies. The rove beetle, Atheta coriaria, is a ground dwelling predator and commercially available. It reduced the number of surviving SWD within infested blueberries 4-7 days post infestation. Entompathogenic nematodes are also commercially available. Direct application of nematodes Steinernema carpocapsae, S. feltiae, and Heterhabditis bacteriophora resulted in no or a single infected larva. Field applications of these nematode species will be unsuccessful given that infection rates were very low in a small and moist arena in the laboratory.