1a. Objectives (from AD-416):
Evaluate the components of the systems approach for sweet cherry, including the use of larval distribution data, chemical controls, and fruit inspection.
1b. Approach (from AD-416):
1. The distribution of cherry fruit fly infestations in orchards will be examined by sampling cherry orchards. 2. Sprays will be made on trees before harvest to determine their effects on fly control. 3. The brown sugar flotation and hot water methods will be compared to determine their efficacy in detecting fly larvae. 4. Modifications of the crushing device and methods will be made with the aim of detecting higher numbers of larvae.
3. Progress Report:
In 2011, detection of cherry fruit fly larvae from crushed cherries using flotation in brown sugar and salt solutions were compared. Cherries were crushed and brown sugar or salt solution was poured over cherries. The solutions were inspected for larvae that were liberated from the fruit. Crushed cherries were preserved in alcohol so that they could be examined under a microscope for larvae that were missed during the initial inspections. The cherries were examined for larvae throughout fall, winter, and spring 2011-2012. Percentages of larvae that were detected were calculated using numbers of larvae initially recovered plus those found in cherries through examinations under the microscope. It was found that the salt method was slightly more effective at detecting larvae than the sugar method, but complete results are forthcoming. A similar test comparing brown sugar and salt flotation when heated and unheated will be conducted. Sweet cherries in three commercial or experimental cherry orchards in Oregon were sampled to document the distributions of infestations. Two hundred cherries were removed from trees along the periphery of orchards as well as trees in the middle and centers of orchards. In one of the orchards, infestations were found along the peripheral trees, suggesting that infestations occurred as a result of flies entering orchards from surrounding non-orchard trees. Studies were conducted on effects of pre-harvest insecticide bait treatments on larval infestations. Cherry trees at the USDA experimental research farm were sprayed with sugar baits containing the insecticide Actara and with the protein-sugar bait GF-120 over the 5-week season and infestations in the cherries evaluated. Actara reduced infestations significantly more than GF-120. In addition, the residual activities of Actara and GF-120 were determined. It was found that Actara in sugar bait had a longer residual activity, possibly explaining its greater effectiveness in controlling flies. A similar sugar bait test was conducted in June 2012. The work reported here addresses objective 5 in the parent project plan.