Listeria in Melons — Fertilizer at Fault?

COMMENTARY | Each time I read news concerning listeria in Jensen Farm’s melons, one word springs to mind; manure. Admittedly, I have my reservations about factory farming. I’ve written on the subject several times. The animal abuse and widespread contamination from factory farms sickens me. Perhaps that’s why when news of the listeria outbreak came out, I pictured fields fertilized with bacteria filled manure. As it turns out, I may be right on the mark with this one. Still, I never assume.

I’ve done the research on the cause of listeria contamination in fruits and vegetables. All my sources concurred. Fertilization with manure from cattle is by far the most common cause. In fact, I failed to find a single source that listed a more probable cause for listeria occurring in produce.


“Animal manure which is frequently used as a fertilizer for growing vegetables and fruits, commonly contains enteric pathogenic microorganisms. These pathogens can contaminate produce during growth in soil. Composting manure can kill harmful microorganisms at specific temperatures and holding times; however, these conditions have not been fully validated.”

John H. Kirk, DVM, MPVM

In his report on pathogens in manure, in regards to listeria, this well qualified veterinarian states, “Fresh vegetables fertilized with animal manure are thought to be important sources of contamination for humans.”

Garden Guides

“The normal source of infection for humans is from ingesting listeria that has come in contact with fresh vegetables.”

Los Angeles Times

“Matching strains of the disease were found on equipment and cantaloupe samples at Jensen Farms’ packing facility in Granada, Colo.”

How would contamination get on equipment? (Admittedly, I am speculating.) Doesn’t it seem likely that farm and processing equipment might routinely come in contact with manure based fertilizer, prior to sanitation of fruits and vegetables? After all, it would be present on the outer part of the produce and certainly in the fields.

I’m not saying that manure based fertilizer is absolutely the cause of the listeria outbreak. I’m simply saying common sense tells me it’s quite possible. Health officials are still investigating the cause of this tragic outbreak. Meanwhile, I’m personally looking at it as just another reason to boycott factory farms. I’ll grow my own, thank you.

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