Thursday, August 11, 2016
Georgia Ballroom (Sheraton Hotel Atlanta)
Sweetpotato, Ipomoea batatas (Olivier), is an important staple food crop in Hawaii and critical to food security in these geographically isolated islands. Production of this crop faces a new challenge from the rough sweetpotato weevil (RSW), Blosyrus asellus, (Coleoptera: Curculionidae). We investigated efficacy of five insecticidal treatments that included four compounds (including one organic bioinsecticide) that were approved already for use against weevils in sweetpotato, plus a control (no insecticide treatment for RSW). Cuttings of sweetpotato cultivar Okinawan were planted on 1 April 2015 at Pepeekeo, Hawaii Island in a field with a history of past RSW infestation. Each plot contained 30 cuttings spaced 0.3 m apart in planting beds spaced 1.5 m apart and 9.1 m long. The five treatments were Belay 16 WSG (Clothianidin; Valent U.S.A. Corp., Walnut Creek, CA), Sevin XLR Plus (Carbaryl; Bayer CropScience, Research Triangle Park, NC), Provado 1.6 flowable insecticide (Imidacloprid; Bayer Crop Science), Botanigard ES (Beauveria bassiana strain GHA; Laverlam International Corp., Butte, MT), and control. The five treatments were repeated four times in a randomized complete block design. Harvesting of Okinawan sweetpotatoes was conducted at 4.5 months before most storage roots were marketable in size due to concerns about the duration of treatment effectiveness. Insecticidal treatments showed statistically significant differences (P<0.01) in percent of all damaged tubers. Plots treated with Sevin or Belay had significantly lower percent of damaged tubers compared to the other three treatments. Each of these treatments appear to be effective in controlling RSW through 4.5 months after planting; however, the duration of the effectiveness of Belay is uncertain, since it was applied only once at planting. Perhaps, a combination of Belay application at planting followed by monthly applications of Sevin from 3 months after planting may be an effective method to control RSW. A second field trial has been installed to confirm these preliminary results.