Midge Flies


Midge FlyMidge Flies, chironomids are commonly found in man made lakes, wastewater facilities and streams with high nutrient content. These flies are similar in appearance to mosquitos, yet do not bite. The midge fly larvae (known as blood worms) feed on the organic debris at the bottom of the body of water and provide a food source for fish and predatory insects. (Apperson 1)

These flies are a nuisance to people who live and work near man made lakes and in Gilbert, recharge facilities. The warm winter temperatures this year created an early midge fly season. Under normal circumstances, staff is able to dry up the basins as the weather warms up. Unfortunately, the nights were warm enough during the winter to allow the midges to hatch before our water demands increased at the customer sites (which reduces flow to the recharge basins). So, Gilbert has been out of balance at that facility. To alleviate the water flows to the recharge facility, we pushed more of the South WWTP water to the north side of town.

A shipment of mosquito fish was delivered and released into the recharge facility this March and we have increased the number of times the fogging contractor treats the site from twice a week (routine year-round schedule) to three times a week- until the basins dry –out. We have also increased our larvacide treatments along the basin edges and inlets to the basins. The basin outfalls (where the canal dumps water into each basin) each now have extended release larvacide briquettes. So, the water is treated as it flows into each basin. We will monitor those and add more if they erode away.

Starting in April, staff started using a different form of treatment in addition to the above items. Each week, the crew sprays down the trees and brush with a %2 solution of dish soap and water. This is a proven environmentally safe method of white-fly and gnat control. It seems to have helped considerably with the adult midges.

This week (May), staff added a different and stronger brand of larvacide chemical for weekly treatments in the canal. Increased larvae control will help interrupt the cycle of midges at the facility. The basins are also drying out faster with the summer customer demand.

There will always be an element of bugs and wildlife around the recharge facilities and parks. Gilbert will continue to provide treatment services and safe methods of midge fly control for the health and comfort of the community.

Advice for neighbors:

  • Use orange or yellow light bulbs in the porch lights and don’t water the grass and plants so much that it stays wet all day long. Midge flies prefer wet vegetation to gather on.
  • If you use a bug zapper, move it as far away from the house that you can. It will attract more of the insects to your area.
  • White or Apple Cider Vinegar mixed 1:1 with water can also be an effective, natural insect repellent.

Apperson, Charles. “Biology and Control of Non-Biting Aquatic Midges.” Residential, Structural and Community Pests. North Carolina State University, July 2006.Insect Notes.5/8/2014. www.ces.ncsu.edu/depts/ent/notes/Urban/midges.htm