Zero tolerance may be the goal in insect and rodent remediation in food plants, but a priority list can be useful when deploying limited resources to combat an ongoing concern.
Thanks to the good folks at FDA, such a list exists. Created two years ago, FDA’s Dirty 22 is a guidance document that identifies the cockroaches, ants, rodents and flies that are critters non gratae in and around production and storage facilities. The species were flagged by FDA field labs because of their links to foodborne diseases.
Given their grazing habits and hairy bodies, filth flies are particularly adept at contaminating food with pathogens. In fact, the majority of the species are flies, a subgroup that could be described as the Filthy 12.
Feces and rotting organic material are breeding grounds and food sources for filth flies, a category that includes house flies and blow flies. DNA evidence implicated house flies in an E. coli O157:H7 outbreak at a Japanese day care center, and highly toxic methomyl pesticide proved inadequate in controlling the flies that descended on the victims of a Korean Airlines crash in 1997. Ten days later, “many bodies had been almost entirely consumed by maggots before they could be recovered,” according to a technical guide from the Armed Forces Pest Management Board.
“Flies have been neglected,” acknowledges Patricia Hottel, technical director at McCloud Services in South Elgin, Ill. “They are such a familiar pest, we sometimes don’t give them the attention they deserve in preventing the spread of disease.”
Cockroaches raise more fear and loathing than filth flies do, “but flies are a much bigger disease-transmitter than cockroaches,” seconds Ron Harrison, director of technical services at Orkin Commercial Services, Atlanta. He lauds the FDA guidance for raising awareness among processing professionals of the food safety danger they pose.
A good offense on the outside of a plant is the best defense against flies inside the facility, and researchers are developing new baits and traps to bolster exclusion strategies. An example of the latter is the Stealth fly station. Entomologists at Ecolab found that female flies in particular are drawn to dark, reflective surfaces, so they designed a trap that frames such a surface with a pesticide-laced border. In a demonstration involving 1,500 flies, the station achieved a kill rate of 85 percent within 50 minutes. Combining the station with a light trap tripled the mortality rate.
Filth flies are exemplars of Charles Darwin’s theory of evolution, leveraging their short maturation cycles to quickly adapt to and resist pesticides. To ensure interventions remain effective, pest control experts recommend rotating baits rather than relying on tried and (up to a point) true remedies.
Two new baits reached the market in the past year: Alpine pressurized fly bait from BASF, with the active ingredient dinotefuran, and Zyrox, a granular bait with cyantraniliprole from Syngenta. They join Maxforce Fly Spot as recent additions to the anti-fly arsenal.
Besides countering flies’ adaptability, the new baits provide some flexibility in how and where they are used. Fly Spot, for example, is for indoor-use only. However, that’s not a green light for applying it in areas where food is processed or handled. Label directions limit applications to office areas and other spaces outside processing and storage areas, points out Chelle Hartzer, product manager-technical services at Industrial Fumigant Co., Lenexa, Kan. “Very few pesticides can be used inside. It’s usually a contamination issue.”
Some indoor pesticides can be applied in employee break rooms, a sometimes overlooked breeding ground. That’s where you’ll find one of Hartzer’s pet peeves. “I hate vending machines,” she says. “They never get moved, they never get washed underneath, and the compressor coils are a great heat source for breeding.”
What lurks below
Small filth flies include fruit flies, phorid flies and drain flies, and drains are a prime breeding area. Few chemical interventions exist, and those available are ineffectual against the flies’ eggs and larvae, observes Judy Black, vice president-technical services at Charlotte, N.C.-based Steritech. As a result, “two days later, the problem is just as bad,” she says.
Regular cleaning and sanitizing is the best defense. Foam is a more effective pesticide delivery medium in drains than liquid, but pesticide treatment is redundant if cleaning removes biofilm that supports both flies and pathogenic bacteria.
Drain inserts are a more effective defense. Originally designed to prevent sewer gases from entering the building, drain inserts also seal out flies and cockroaches, another pest that often gains entry through drains, particularly after heavy rains.
Trap Guard from ProVent Systems Inc. is a popular choice among pest-management professionals. The insert’s elastomer tail curls up and seals off the orifice unless there is downward pressure from wastewater, whether it’s a trickle or a torrent. However, weekly cleaning still is recommended.