Submitted to: Biological Control
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/23/2003
Publication Date: 3/1/2003
Citation: Yee, W.L., Lacey, L.A. 2003. Stage-specific mortality of Rhagoletis indifferens (Diptera:Tephritidae) exposed to three species of Steinernema nematodes. Biological Control. 27:349-356. Interpretive Summary: The western cherry fruit fly, Rhagoletis indifferens Curran, is the major pest of sweet cherries in the Pacific Northwest. Currently, the only method for controlling the fly is through use of insecticides. Personnel at the Yakima Agricultural Research Laboratory in Wapato, WA, conducted laboratory and field experiments to test the use of nematodes as a possible alternative to insecticides for fly control. Results indicated that nematodes were highly effective in killing larvae of flies (62-100% mortality), were not effective in killing pupae (transitional stage), and were moderately effective in killing adults. Effectiveness also depended on the species of nematode. These findings are helpful in developing methods to use nematodes for control of cherry fruit flies and ultimately may result in reduced insecticide use in cherry orchards.
Technical Abstract: Mortality of larval, pupal, and adult western cherry fruit fly, Rhagoletis indifferens Curran, exposed to the steinernematid nematodes Steinernema carpocapsae (Weiser), S. feltiae (Filipjev), and S. intermedium (Poinar) was determined in the laboratory and field. Larvae were the most susceptible stage, with mortality in the three nematode treatments ranging from 62 to 100%. Steinernema carpocapsae was generally more effective against larvae than S. feltiae, with 100 infective juveniles (IJs)/cm2 being more effective than 50 IJs/cm2. Mortalities of R. indifferens larvae at 0, 2, 4, and 6 days following their introduction into soil previously treated with S. carpocapsae and S. feltiae were 77-100 and 40-90%, respectively. There was no decline in mortality caused by S. carpocapsae as time progressed, whereas there was in one test with S. feltiae. Larval mortalities caused by the two species were the same in a 1:1:1 vermiculite:peat moss:sand soil mix and a more compact silt loam soil. In the field, S. carpocapsae was slightly less effective than S. feltiae against larvae. Pupae were not infected, but adult flies were infected by all three nematode species in the laboratory. Steinernema carpocapsae was the most effective species and at a concentration of 100 IJs/cm2 infected 11-53% of adults that emerged. The high pathogenicity of S. carpocapsae and S. feltiae against R. indifferens larvae and their persistence in soil as well as efficacy in different soil types indicate both nematodes hold promise as effective biological control agents of flies in isolated and abandoned lots or in yards of homeowners.