What are flies?
There are several flies that are pests in agriculture, horticulture and mushroom cultivation. Species that can cause damage or nuisance, are particularly small flies of the families Sciaridae (sciarid flies) and Ephydridae (shore flies). The larvae of these insects generally live on rotting plant material and are mostly found in the soil. The spotted wing drosophila, Drosophila suzukii, has recently developed into a major pest on soft fruits in Europe and North America. Sciarid flies and shore flies are mainly a problem in greenhouses. Their larvae live in the ground and prefer moist substrates that is rich in organic matter. Although they cause little direct damage to plants, they are often a problem due to their large number. Larvae of flies of the family Keroplatidae (mainly Lyprauta sp.) can cause damage in potted orchids. The Spotted Wing Drosophila has recently invaded Europe and the Americas where it is causing serious damage to many soft fruit crops.
Flies can cause damage to crops both directly and indirectly. The type of damage depends on the species of the flies. Direct damage is the immediate result of larvae feeding on root hairs and tender roots as well as stem and leaf tissue and fruits. The lesions caused by feeding larvae provide invasion routes for various pathogenic fungi, for instance Fusarium sp. And Botrytis sp. Adults can also spread pathogens from diseased to healthy plants. Frass deposited on leaves or flowers in ornamental crops, lettuce, and herbs also causes cosmetic damage, and sometimes this can occur on such a scale that growth, particularly of young cuttings, can be retarded.