SF6023 - Evaluation of Pesticide Solutions in the Transmission of Pathogenic Bacteria to Horticultural Crops

Researcher:

Dr. Richard Holley, Dept. of Food Science, University of Manitoba

Objectives:

Evaluation of potential food safety risks associated with the spraying of pesticides, prepared using on-farm water of unknown bacteriological quality, onto horticultural crops.

Expected Benefits:

1. Identification of pesticides requiring special handling or caution with respect to mixing and storing.
   

2. Manufacturer responding to possible problems via inclusion of biocides or warning labels or a re-examination of their formulation ingredients.
   

3. Current assessment of the potential hazard situation and possible explanations to previous foodborne outbreaks involving fruit and vegetables.
   

4. Future research to investigate factors or ingredients in pesticides, which have the potential to encourage pathogen growth: bacterial and or protozoan.

Summary of Research Results:

During the past two decades, the consumption of fruits and vegetables has increased in Canada. Meanwhile, foodborne illness associated with fresh produce has also increased. Concern that pesticides might be a vehicle for pathogen contamination of produce stimulated work reported here to evaluate the potential for bacterial growth in pesticides diluted as used on the farm. The ability of Salmonella, E. coli, Listeria and Shigella to survive or grow in 7 pesticides used by the horticultural industry in Ontario was examined. In the laboratory, except for Bravo 500, most pesticides tested were somewhat inhibitory to the harmful bacteria. Among all bacteria, Salmonella was best able to survive and Listeria was least able to survive in pesticides. Generally, bacteria survived poorly in pesticides at higher temperatures or pesticide concentrations. In the field, after a recommended day-to-harvest interval of one day, E. coli and Salmonella could be recovered from sprayed tomato plants. E. coli and Salmonella in water survived longer than in Bravo when sprayed on the plants, and persisted up to 26 and 56 days, respectively. Results also indicated that use of pesticides beyond their expiry dates may make it easier for undesirable bacteria to grow.