What are Fever Flies?

The Fever Fly is a Bibionid fly. Adults are black and hairy with short wings and are seen in swarms hovering over lawns on sunny days. Whilst the adult flies cause no damage, they lay eggs between May and September and the larvae that hatch in the late summer are a problem. The larvae spend the autumn feeding on organic matter in the soil and on the roots of growing turf. The damage caused by this feeding will be seen in mid-winter with the main symptom being a general yellowing in patches across the lawn. In extreme cases these patches will die off completely.


We recommend using a broad spectrum insecticide (such as Sven) in conjunction with a wetting agent, such as Abzorb Triple Action Wetting Agent. It is best to apply this in November/December time as the larvae are smaller and near the surface of the rootzone, therefore making them easier to target. If you leave the application to January/February, the larvae will be bigger and deeper into the soil making it harder to apply the chemical.


We recommend using a broad-spectrum insecticide, for example Sven, alongside a wetting agent in November/December. Abzorb Triple Action Wetting Agent is ideal as it contains and blend of soil penetrating surfactants. 

For more information on controlling Fever Fly Larvae, please get in touch with our sales team on 01522 246491.