Greenhouse - Shore Flies vs Fungus Gnats

Greenhouse growers sometimes have a hard time telling shore flies, a nuisance pest, from fungus gnats that can damage plants. The following is a short article on the subject from the University of Maryland.

We are receiving a lot of reports from greenhouses and garden centers that shore fly adults are all over the foliage of their plants, especially on zinnias, begonias, and osteospermum. We just went through two weeks of cool, rainy weather which is ideal for algae growth. Algae is what the larval stage of shore flies feed and thrive on, resulting in the increase of adult populations that we are seeing this week. Growers often have a hard time telling shoreflies apart from fungus gnats on their sticky cards. Shoreflies are nuisance pests, but fungus gnats damage plants by feeding on the roots and tunneling into the stems. Some ways you can tell them apart are that fungus gnats have slender bodies, a Y-shaped pattern on their wings, and the larvae have a black head capsule. Shorefly adults have more robust bodies, 5 white spots on their wings, and Note the 5 spots on the wings the larvae lack a black head capsule.

Reprinted from the April 18, 2008 edition of the Greenhouse TPM/IPM Weekly Report from the University of Maryland Cooperative Extension http://www.ipmnet.umd.edu/08apr18G.pdf