Location: Fruit and Vegetable Insect Research
2013 Annual Report
The project goal is to evaluate methods to reduce the chances of cherries being infested by larvae of cherry fruit fly, without the use of methyl bromide. Cherry fruit fly is a major quarantine pest of sweet cherries in the Pacific Northwest of the United States and methyl bromide is a fumigant that is used to kill its larvae inside cherries. However, methyl bromide is being phased out due to its harmful environmental effects. In addition, it reduces the shelf life of cherries. Technical objectives are to evaluate (1) the use of larval distribution data, (2) chemical controls, and (3) fruit inspection for showing the absence or unlikelihood of cherries being infested with cherry fruit fly larvae. We determined fly larval distribution patterns in two chemically managed sweet cherry orchards in Hood River, Oregon. Forty trees were trapped and sampled for fruit from each orchard. Larvae were reared from fruit. We identified the border trees of orchards as being more infested with adult and larval cherry fruit flies than interior trees. We determined the chemical control methods that are most effective for killing adult flies and preventing them from laying eggs into fruit that lead to larval infestations. We also determined the best insecticides to use on unpicked cherries in orchards after cherry harvest to kill any larvae inside fruit. Finally, we completed evaluation of 4 postharvest detection methods for detecting cherry fruit fly larvae using cherries obtained from 10 cherry trees. Cherries were crushed and placed in brown sugar or salt solution, causing larvae in cherries to float to the surface of the solutions. We showed that salt and sugar solutions were equally efficacious, resulting in larval detection rates of >90%. Salt also had the benefit of being much less expensive. We met all the technical objectives, and showed that sampling borders of cherry orchards may be the best way to detect larval infestations or to concentrate chemical sprays; that chemical methods are available to control flies; and that inspecting cherries using brown sugar or salt solutions is highly effective at detecting fly larvae. This addresses the overall project goal by providing data implying that methyl bromide may not need to be used on cherries when this information is utilized. Our results suggest that these detection methods may be used to determine the absence of the insects in cherries, and negate the need for a fumigant such as methyl bromide.