Using food-grade surfactants, Agricultural Research Service (ARS) researchers in Wapato, Wash., are testing a new method of ridding packed sweet cherries of mites, thrips and other surface-feeding pests.

As per ARS entomologist Jim Hansen, such pests pose more of a consumer-marketing problem than a field-production one, since they can occur on sweet cherries that have been packed for domestic sale or export. In addition to culling and sorting measures, Hansen is experimenting with dips, baths and sprays containing polydimethyl silicone emulsions and other food-grade surfactants, which, in effect, wash the pests off the cherries' surface.

Surfactants are typically used as wetting or dispersing agents in products ranging from soaps and shampoos to paints and insecticides. But recent studies by Hansen and others have shown that some silicone-based surfactants will remove spider mites, thrips and mealy bugs from apples and pears.

Hansen's surfactant studies at ARS' Fruit and Vegetable Insect Research Unit in Wapato kicked into high gear in 2005 when ARS entered into a research agreement with the California Cherry Advisory Board (CCAB). The collaboration makes sense since Washington and California are the nation's top two sweet cherry producers, exporting more than half their fresh-market harvests.

Besides fruit quality, the success of international sales hinges on U.S. cherry exporters' ensuring pest- and disease-free shipments to avoid rejection or delay of the shipments at the trader's port.

Under the ARS-CCAB agreement, Hansen is conducting research to identify emulsifiers and other surfactants that will remove a variety of pests. He's also looking for ways to identify exposure times that won't delay online packing operations, as well as ways to compare the effectiveness of spraying cherries versus immersing them in surfactants. In a supporting study, Hansen's collaborators at the University of California-Davis examined surfactant-treated cherries for fruit damage, but they found nothing significant.