What are Shore Flies?
If you don’t have a greenhouse, you may not know about shore flies (Scatella stagnalis). They are one of several types of insects that are nuisance pests in areas that get excess water, like greenhouses. Shore flies have short antennae like the fruit flies that they resemble. They are very strong fliers and have dark wings with five light spots on each one. Shore flies also look a little like fungus gnats, another greenhouse and indoor nuisance pest, and are often confused with them. While fungus gnats feed on crop roots, shore flies do not. They are attracted to greenhouses with standing water and eat the algae there.
Shore Fly Damage
If shore flies don’t eat the crops in greenhouses, why should gardeners be concerned with their presence? Really, they are more a nuisance than a pest that damages crops, doing only aesthetic damage. If you have a heavy infestation of shore flies in your greenhouse, you may notice black “fly specks” on leaves. The spots are unsightly but nothing more. In fact, even the larvae of shore flies are algae feeders, and don’t feed on crops. The adults, however, may transmit root disease organisms.
Controlling Shore Flies
Shore fly control can be achieved, to some extent, by limiting algae growth. You can take many steps toward this end, including using less fertilizer and not overwatering. It also helps to repair leaks in hoses or irrigation systems to prevent standing water. Another step toward controlling shore flies in greenhouses is to clean algae off the walls, floors, gutters, and benches. Some gardeners use steam cleaners. So how to get rid of shore flies once and for all? If you really are ready to leap into shore fly control, you may want to consider insecticides. Many types of insecticides will take out shore flies in their larval stages but won’t affect the adults. If you want to try controlling shore flies with insecticide, you’ll need to use both an adulticide and a larvicide for well-established populations.
