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Open Access Publications from the University of California

Food Safety and Rodent Control in Leafy Green Crops


In 2006, spinach contaminated with Escherichia coli resulted in the death of 3 people and over 200 illnesses. The contaminated spinach was traced to a field in central California. In 2007, produce industry representatives developed safety guidelines (known as the Metrics) for lettuce and other leafy green crops. The Metrics addressed encroachment and crop contamination by wildlife and livestock. Rodents are treated by growers and buyers as suspects in the food-borne illness matrix. This has resulted in many unnecessary, ineffective, and expensive rodent control practices in leafy green crops. The Metrics require periodic monitoring of animal activity in and around the crop fields, but there are no specific guidelines on how to monitor for rodents. In 2009/2010, we conducted field work in the Salinas Valley region of Monterey County. This included surveying iceberg lettuce and spinach fields to identify the rodents present and test rodent monitoring techniques. As a result of this fieldwork, a specific index of abundance calculation was developed to enable growers to accurately assess the rodent population in their fields. We reviewed the Metrics and identified all portions related to rodents and rodent control. Monitoring techniques were evaluated for their practicality and ability to detect rodents. Control strategies from the California Vertebrate Pest Control Handbook (CDFA 2008) were combined with the results of the monitoring program to create a pocket-sized field guide containing relevant monitoring and control information regarding rodents and leafy green production.

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