Sunday, January 11, 2009

Shore Flies Indoors

Picture of adult shore fly. Photo on:

Shore flies are usually found in greenhouses, since they are attracted to algae growing on potting soil and under greenhouse benches. However, they can be found living on many house plants as well. Shore flies are frequently confused with fungus gnats, since they are usually found together. However shore flies have short antennae, a large head with red eyes, and smokey gray wings with 5 white spots on each wing. Also shore flies are stronger fliers than fungus gnats.
Female shore flies will lay eggs singly on the surface of algae. The eggs will hatch in about 2 to 3 days. The larvae will be found on the top layer of potting soil, feeding on the algae. Shore fly larvae are 1/8 inches in length, with a brownish-yellow, legless body. The larvae do not have a distinct head capsule, but their dark mouthparts and internal organs may be visible. The larvae mature in 3 to 6 days and then pupate. The pupae are also found close to the soil surface. The adult fly will emerge 4 to 5 days later and it will feed on the same materials as the larvae. The adult fly usually stays close to the breeding sites.
Eventhough the shore fly adults and larvae do not feed on plants, they still can present problems. Adults can be a problem, since they can transmit plant pathogens, such as Pythium and other root disease organisms. Also the shore flies’ excrement can land on foliage and leave unsightly black specks.

Some Control Options:

Some Non-chemical Control Options:

1) Avoid over watering and limit fertilizer run-off. Allow soil to dry before watering again.
2) Algae should be removed from under and on benches, walls, and floors.
3) Compost should be aerated often and relocated away from doors and windows.
4) Pasteurized container mix should be used or treat potting soil with heat or steam before using it.
5) Remove standing water and eliminate any plumbing or irrigation system leaks.

Some Chemical Control Options:

Some chemical control options include using such active ingredients as bifenthrin, permethrin to control adults and azadirachtin, kinoprene, diflubenuron, or cyromazine to control larvae.

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