The Issue

A food plant, serviced by Batzner, discovers a moth fly infestation in and around their plant. Never having experienced a moth fly infestation to this extent, the plant was forced to shut down for a week. As the moth fly population increased, so did their need for a solution. That’s when they called in Skie Gierach, one of Batzner’s Operations Managers, to perform a thorough inspection of the property and to locate the source.

The Inspection

Since moth flies are typically associated with sewage beds, where their larvae feed on sludge and organic matter, Skie first performed an inspection of the septic tank. Upon discovering the septic tank was not responsible for the massive swarms of flies, and knowing the facility used a lagoon down the road to hold water, Skie headed toward the water source. As he drove, Skie noticed the density of the moth flies increased as he closed in to the proximity of the lagoon and a nearby farm field.

The Surrounding Area

Holding more than 500 million gallons of water, the lagoon consisted of waste water from the plant. This water was recycled and used to irrigate the nearby farm field. Combined, the lagoon and farm field were approximately 600 acres.

The Issue Discovered
It was discovered, that due to a lack of aeration in the lagoon, organic matter began to buildup on the surface. The combination of stagnant water and warmth from the sun encouraged the organic growth, and in return, provided the ideal environment for the moth flies to flourish. However, the lagoon wasn’t the only site. The lagoon water used to irrigate the farm field, which was already saturated with water, provided even more organic buildup, creating a second location for the flies to reproduce.
Problems for the Food Plant

At night, the lights from the food plant attracted the flies to the building. The lights, in combination with strong winds, caused the flies to settle on the outside of the building, breeding in any organic water they could find, including puddles on the roof. Moth flies on the roof were sucked inside through the HVAC system.


In order to eliminate this infestation in the quickest way possible, two treatments of larvicide were applied to the lagoon to prevent hatching. A treatment, using a gas granular spreader, was evenly applied around the perimeter of the lagoon. The nearby farmers also contributed by treating their field, weekly. Eight insect light traps were added to the existing 20 that the plant already had. The weeds and organic buildup on the roof were treated and daily exterior treatments were applied around the doors to reduce the number of flies on the building and to prevent them from getting inside. The moth flies were eliminated in 30 days.

Moth Fly Infestation at a Food Plant in Wisconsin

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