By Tory Schmidt, Washington State Tree Fruit Research Commission

Cherry growers have a lot on their plates at this time of year:  staying ahead of powdery mildew, watching for Spotted Wing Drosophila, keeping a wary eye on the rain clouds, and figuring out how to hire enough pickers to get the crop off their trees.  The last thing anyone wants to worry about is whether a shipment of their fruit might be rejected halfway around the world because some faceless, nameless bureaucratic has determined they used too much of a particular pesticide.cherry with residue

In order to avoid such a disaster, cherry growers require a lot of complex, up-to-the-minute information to make appropriate management decisions.  Specifically, they need to know exactly where their sales desks intend to export their crop, what is the most current Maximum Residue Levels (MRLs) allowed for every pesticide they apply in each of those foreign markets, AND have a reasonable idea of what residue levels are present for each of those pesticides on their fruit at harvest.  Fortunately, there are resources available to help growers navigate this thorny regulatory thicket.

The Northwest Horticultural Council (NHC) has done great work through the years to help with a wide range of regulatory issues in foreign and domestic markets.  The NHC has been an important advocate for Northwest growers in helping resolve trade disputes and pushing successfully for the publication, standardization, and in many cases, relaxation of MRLs posted in several foreign markets for numerous chemicals important to growing apples, pears, and cherries in our region.  Further, they provide a great service to industry by publishing an updated list of important MRLs in key export markets (http://nwhort.decisionaid.systems/ui#topmarkets). You can also find current MRL information for virtually any pesticide applied to any crop for almost any foreign market at the following website sponsored by Bryant Christie: https://www.globalmrl.com/

For several years, the Washington Tree Fruit Research Commission (WTFRC) has supported projects to develop more information regarding residue levels produced by typical apple and cherry spray programs.  Their work has indicated that pesticide residues on cherries are not consistently reduced by the hydrocooling and packing process, suggesting that producers should not rely on such measures to ensure their fruit meets certain residue standards.  WTFRC studies have also found that use of rain protectants like RainGard and Parka can sometimes preserve pesticide residues, especially for materials applied within a few weeks of harvest.  Since 2011, they have applied more than 30 commonly used insecticides, miticides, and fungicides on commercial cherry orchards to determine harvest residue levels.  While most findings have been below most export MRLs, some products have consistently produced residues that exceed tolerances in some conservative markets; based on WTFRC results, cherry growers should be very careful with use of Centaur, Danitol, TopGuard, and Quash (especially in combination with rain protectants) if they hope to export their fruit all markets. Detailed information on all WTFRC studies on apple and cherry pesticide residues are available at the homepage of their website http://www.treefruitresearch.com/.

Finally, one of the surest ways for cherry growers to determine their precise pesticide residue levels is to have their own fruit tested by an analytical lab.  Pacific Agricultural Laboratory (PAL) (http://pacaglab.com/) is the leading service provider in the Northwest for analysis of pesticide residues on fruit crops.  Cherry growers or warehouses can ship fruit samples to PAL’s lab outside of Portland and typically expect results back within 1-4 working days, hopefully in time to help determine where their fruit should or should not be shipped.

Growing, packing, and marketing cherries is stressful enough without the additional worry of complying with constantly changing MRLs – hopefully these resources can help you along the way.

Contact

SchmidtTory Schmidt

Project Manager

Washington State Tree Fruit Research Commission

tory@treefruitresearch.com