Midges and filter flies are more than a nuisance at wastewater treatment facilities. Their aquatic larvae consume beneficial organisms, deplete water of oxygen and create floating mats of larval and pupal casings. In severe infestations, these pests can alter water quality, clog pipes/equipment, transmit pathogens and generate complaints from the public.
Control of these pests begins with proper identification and an understanding of their life cycles.
Science lesson
Chironomid midge flies, or midges, lay egg masses — containing up to 3,000 eggs — on the water’s surface. Eggs sink and hatch within a week, and the larvae burrow into sludge, establishing small tubes where they develop into a dark red worm-like stage. This stage lasts two to seven weeks, depending on water temperature, before the adults emerge. Adults resemble mosquitoes with bushy antennae, and they are ready to reproduce within days.
Filter flies, also known as drain or moth flies, are also frequently found in wastewater treatment facilities. After a two-day incubation, eggs hatch into small, pale larvae that feed on slime layers or nutrient-rich films in treatment beds. After a nine- to 15-day feeding period, they pupate and emerge as flies with a hairy appearance and pointed moth-like wings. Adults live for a few days, during which time females lay between 10 and 200 eggs.
For effective control, operators need to break the life cycle. Strike products interfere with larvae development, eventually killing flies in the pupal stage. Because adults or larvae that have pupated are not affected, population reduction occurs two to three weeks after treatment. Continuous treatment ensures these pests will not rebound to reach infestation levels.
Strike products
Strike products are available in three options:
Strike Professional Midge Control (Liquid) is a microencapsulated formulation that is time-released for downfield control, making it ideal for facilities with chironomid midges in various stages and areas. Strike Liquid is added after sand and grit have been removed from the main channel, upstream of midge fly breeding. It must be introduced far enough ahead for the material to properly mix in the water, before the primary clarifiers. Typically this application controls midges through secondary clarification. Depending on holding times and flow, Strike treatment can control midges in tertiary treatment. However, it might be necessary to set up another injection point or treat with Strike Pellets.
Strike Ultra (Liquid) is a water-dilutable, emulsifiable concentrate that is ideal for treating trickle filters and smaller areas where flies are a problem. Strike Ultra Liquid isn’t microencapsulated, so control downfield is reduced. Strike Ultra Liquid is an economical solution at facilities where fly breeding is concentrated and contained to a defined area.
Strike Pellets offer control in areas with extended holding times. In some cases, lagoons and ponds can be treated with a 20-foot perimeter band of Strike Pellets. It is always best to treat the entire surface area.
All Strike formulations can be applied to biosolids drying beds. Liquids can be metered into the sludge flow, while pellets can be spread over beds. Flies are controlled as biosolids dry. When applying to trickle filters, use liquid formulations during low flow — typically overnight — with a metering device.
Strike is a product of the Central Life Sciences strategic business unit of Central Garden & Pet. Central Life Sciences creates healthier environments and makes life better for people, plants and companion animals around the world.
321/480-0478 • mwhitson@central.com • www.strikeproducts.com