In response to industry concerns about maximum residue levels, or MRLs, the Washington Tree Fruit Research Commission in Wenatchee began conducting trials last year with commonly used apple and cherry insecticides and fungicides.
The commission repeated the trials this year featuring 11 insecticides and eight fungicides commonly used in Washington orchards, according to a news release.
The study factored in different use patterns and the effects of washing and packing.
It also examined the use of carbaryl, marketed as Sevin, only as a chemical thinner early in the growing season.
Although none of the residue levels exceeded U.S. tolerances for apples, some did exceed some foreign MRLs, which are set much lower than Environmental Protection Agency limits.
Both standard and aggressive use of Diazinon 50W, Thionex 50W, Topguard, Danitol and Inspire Super programs exceeded MRLs of some countries, according to the release.
Although washing fruit, as would occur during packing, did reduce residue, it wasn't consistent enough to be relied on as a management strategy.
Use of carbaryl late in the season as an insecticide did produce residues that exceeded some MRLs, but use of it only as a chemical thinner resulted in no detectable residues.
The researchers saw similar patterns in cherries, with residues exceeding some foreign MRLs. Among those products were Mustang MAX, Entrust, Danitol 2.4EC, Carbaryl 4L, Belt, Orbit and Pristine.
Rinsing the fruit in a commercial hydrocooler did little to reduce detectable residue levels.
Visit the Northwest Horticultural Council for a listing of foreign MRLs.