Plant Problem Diagnosis Key / Pests
Pest
Shore flies
Scatella spp.
Stout dark flies that breed in algae on wet media, benches and floors. They do not feed on roots, but their droppings mark leaves and they can carry root-rot spores.
Signs
- Housefly-shaped adults with short antennae and five pale spots on each wing.
- Green algae on media and floors where they gather.
- Small black dots of droppings on leaves.
What favors it
Algae on wet media, benches, floors and drip lines.
Prevention
- Cut back on standing water and drip leaks.
- Keep floors and benches dry; clean algae off between crops.
- Limit fertilizer runoff.
Often confused with
Sources
- Fungus Gnats and Shore FliesUMass Amherst Extension
- Managing Shore Flies in the GreenhouseUConn Extension
- Fungus Gnats and Shore Flies (E-111)Purdue Extension
Treatment by crop
Cultural, biological and chemical options in the order to use them, and notes written for each crop.
Identification is free. Treatment is on the Home and Pro plans.
Questions in the key that lead here
- Look the plant over, leaf undersides included. Are insects, mites, slugs, eggs, webbing or droppings on it?
Yes, something living or its traces - What is on the plant?
Small insects, clustered or flying - Do they fly up when the plant or the soil is disturbed?
Yes, they fly - What do they look like, and where are they?
Dark, gnat-like, around the soil surface - Look closely at the adults, or at a sticky card.
Stout, like a tiny housefly, with pale spots on dark wings
Not a match? Start the key or describe what you see.
More photos
More from university Extension: search Extension pages on shore flies, or find a plant diagnostic lab through your state's Extension.
Other pests
- Aphids
- Bagworms
- Bark beetles of pine and spruce
- Broad mites and cyclamen mites
- Caterpillars
- Cicada and twig-cutting damage
- Colorado potato beetle
- Cucumber beetles
- Cutworms
- Elm leaf beetle
- Emerald ash borer
- Flea beetles
- Fungus gnats
- Galls on leaves and twigs
- Hemlock woolly adelgid
- Japanese beetles
- Lace bugs
- Leafminers
- Mealybugs
- Pine sawflies
- Root aphids
- Root-knot nematodes
- Russet mites
- Sapsucker damage
- Scale insects
- Slugs and snails
- Spider mites
- Spongy moth (gypsy moth)
- Spotted lanternfly
- Squash bugs and stink bugs
- Squash vine borer
- Tent caterpillars and fall webworm
- Thrips
- Whiteflies
- Wood borers