Get control of a phorid fly infestation

Dr. Jamel Sandidge, BCE, Research Entomologist, Rockwell Laboratories

When the call comes in to eliminate an infestation of Phoridae — phorid flies, also known as humpback, scuttle or coffin flies — you may have a lengthy battle on your hands. Phorid flies reproduce rapidly, and have the ability to breed in just about any decaying organic matter, whether it’s the scum at the bottom of a trash can, a dirty mop head, an overwatered plant, or a dead body. Once phorids establish and spread throughout a structure, potential breeding sites can be found everywhere.

As when dealing with any small fly infestation, the primary objective is to find and eliminate the areas where they breed, stage, rest and feed. Start your search in areas that provide major sources of moisture and organic material, such as drains, potted plants, trash cans, grease pits, garbage chutes and disposals, and other kitchen equipment. Then expand the search to include:

• Areas that accumulate smaller organic particles, such as broken floor tiles, mops and mop buckets, brooms, floor mats, etc.
• Recently purchased items that could be a source of the infestation; bags of mulch, potting soil and compost are often primary sources.
• Dead animals, from a rodent job or other sources, that haven’t yet dried out.
• Chronic leaks and condensation in areas such as around heating, ventilation and air-conditioning (HVAC) equipment, refrigerator drip trays, leaky pipes, broken sewage lines, etc.

I recommend a control program that includes:

• Resolving any moisture and/or leak issues, and thoroughly clean affected areas when possible.
• Using bio-sanitation products containing beneficial waste-digesting microbes in areas with chronic moisture and organic debris. Apply them as a foam, liquid or mopping solution, or in the form of slow-dissolving blocks that are placed in areas with water flow, such as drains and traps.
• Applying a boric acid-based insecticide to breeding areas to kill larval and adult stages.
• Installing an insect light trap (ILT) to help reduce the adult phorid population.

Finding one breeding/feeding source doesn’t mean you’ve found them all, so look for other areas if the infestation continues.