Utah Pest News Summer 2010


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Invasive Vinegar Fly Threatens Western Fruit Crops

Drosophila suzukii raspberry fly trap


Trap captures of the invasive vinegar fly, spotted wing drosophila (SWD, shown at left) (Drosophila suzukii), are on the increase in California and Oregon in 2010.  This insect caused substantial fruit crop losses in these two states in 2009, and there is concern that infestations are spreading this year.  Dr. Cory Vorel, USU Cooperative Agricultural Pest Survey Coordinator, has placed monitoring traps (shown at right) in 10 orchards in northern Utah, encompassing key fruit production areas of Box Elder, Davis, Weber, and Utah counties.  No SWD have been caught in Utah to date.  Traps contain either apple cider vinegar or a yeast-sugar water solution.  All tree and small fruits, and vegetable fruits, such as tomato and pepper, are hosts for SWD.  SWD is of particular concern as a fruit pest because the female inserts eggs into fruit as they ripen on the plant.

Oregon State University is recommending that sweet cherry growers reduce SWD populations in the early season with insecticides.  Utah fruit producers applying insecticides for other insect pests, such as cherry fruit fly, raspberry horntail, or peach twig borer, should consider using insecticides with activity against SWD in case the insect is present.  Cherry fruits become susceptible to SWD beginning at light straw color; slightly less mature than when they become susceptible to cherry fruit fly.  Insecticides with documented efficacy to SWD include acetamiprid (Assail), spinetoram (Delegate), spinosad (Entrust, Success), imidacloprid (Provado), carbaryl (Sevin), malathion (Malathion), azinphosmethyl (Guthion), and most synthetic pyrethroids.  Avoid overuse of pyrethroids, malathion, and carbaryl as they can flare spider mites.  Rotate chemical types and be mindful of re-entry intervals (REIs), pre-harvest intervals (PHIs), and maximum residue limits (MRLs) when selecting products to use.

-Diane Alston, Entomologist