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Irrigation of fruit, vegetable crops is food safety matter

July 7, 2016

Indiana fruit and vegetable growers bringing irrigation systems into operation as production gets into full swing should have their water tested as part of good agricultural practices for produce food safety, Purdue Extension food safety educator Scott Monroe says.

Testing water is one of the most important things growers can do to minimize the risk of microbial contamination in growing crops, Monroe said. Water is used for multiple operations in fruit and vegetable production, making it a potential medium of transfer for foodborne illness.

“We use water for irrigation, pesticide application, frost protection and washing and packing, and many other uses,” he said. “The amount of uses and the potential for carrying human pathogens makes water a major food safety focus.”

Growers who meet certain criteria under the Food and Drug Administration’s Food Safety Modernization Act Produce Rule, which took effect in January, must test water that is applied to harvestable portions of growing crops. Monroe noted that the new regulations require frequent testing over two years to establish a baseline, with periodic testing required thereafter.

While some growers may be required by the produce rule to do extensive testing, Monroe said it is a good idea for all produce growers to test their water.

The frequency of testing is determined by the water source. Surface water is generally unprotected and carries a greater risk for contamination.

“Consequently, growers using surface water instead of underground water need to have water tested more frequently,” Monroe said.

Growers using municipal water do not need to have their water tested because the utilities are legally required to do that.

All water used for fruit and vegetable production and postharvest processing should be tested for generic E. coli, Monroe said. Generic E. coli testing will indicate potential presence of disease-causing organisms.

“If E. coli is present in a water sample, it means that the water source has fecal contamination and may, by association, harbor human pathogens,” he said. 

Water samples can be submitted to any certified lab for testing. Monroe said it is important to make sure samples are sent to a certified lab.

“Always communicate with the lab to make sure they understand what the water is being used for and what test is required,” he said.

Interpreting lab results is also very important. Monroe said water used for production should not exceed 126 cfu/100 ml generic E. coli.

Water used for postharvest operations must not contain any detectable generic E. coli. If water exceeds allowable limits, growers will need to treat it or find another water source.

“While a bad test will not put a grower out of business, it does indicate a risk factor that needs to be dealt with and mitigated,” Monroe said.

Produce growers who have food safety questions concerning water use and testing can contact Monroe at the Southwest Purdue Agricultural Center at 812-886-0198 or by email at jsmonroe@purdue.edu.

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