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Growers using Washington State University’s online Decision Aid System this season will be able to consider pesticide maximum residue limits (MRLs) of top foreign markets when they make their crop protection chemical decisions.

In recent years, producing fruit for export markets has become more complicated because pesticide registration and setting of residue tolerances is done on an individual country basis and not universally. This has made it a challenge for growers to stay on top of MRLs in foreign markets.

Several years ago, the Northwest Horticultural Council developed a comprehensive database to track pesticide registrations and MRLs of Codex, the United States, and foreign countries. Though Codex was created by the Food and Agriculture Organization and the World Health Organization to provide international standards and guidelines relating to foods, many countries adopt their own, more stringent standards.

The Hort Council’s database, publicly available on their Web site, has been incorporated with computer model output on WSU’s DAS program. The DAS program uses weather and environmental data to provide growers with real-time pest information, such as stage of development based on growing degree-days, and includes a mini spray guide to help choose appropriate pesticides. MRLs for top export markets will be part of the DAS mini spray guide. Links to the full MRL database for all foreign markets will be part of the DAS Web page and the full WSU spray guide.

Dr. Michael Willett of the Hort Council said the MRL interface with DAS will be very useful to growers when they are looking at the WSU spray guide list of recommended chemicals. “Growers will be able to know if there is an issue with certain chemicals in export markets at the time they are making crop protection decisions.”

Ute Chambers, DAS manager and educator, said that in the near future, they hope to have the MRL information available through smartphones, allowing growers to access information in the field. The DAS program is free but requires users to register.

To see the full MRL database, visit To learn about DAS, go to