Sciarids: solani, Lycoriella mali и Lycoriella auripila;
Phorids: Megaselia halterata и Megaselia nigra
Cecids: Heteropeza pygmaea, Mycophila speyeri и Mycophil barnesi
Various species of flies are among the most dangerous mushroom pests. They all belong to a group of insects called "dipterous" (double-wing) due to the fact that adult flies that are similar in size and color – have two wings.
Mushroom flies on mushroom fruit bodies
Mushroom flies on mushroom fruit bodies.
In literature, a rather detailed description of each species can be found, with the help of which, the flies present on your farm can be identified. A correct identification of the pests is necessary for the correct choosing of control methods depending on the cycle and the development properties of each species.
Attracted by the smell of compost and growing mycelium, flies get inside the growing rooms through every possible openings and cracks and lay eggs into the substrate, casing layer and on fruit bodies. At favorable conditions larvae appear from the eggs after 5-10 days and cause great damage to the mushrooms. Larvae feed on mushroom mycelium and gnaw the pins. Developing pins and young mushrooms are smaller than ripe mushrooms and therefore, they don’t survive after the larvae attack. The damage of mycelium can also be very severe, which results in the formation of pins brown in color and having a leathery surface. Moreover, young mushrooms become hollow and shrink, or die. This kind of damage is very guileful, since it happens when the larvae population is not dense enough for the appearance of holes in the stipes, and so, it can happen unbeknownst to the mushroom grower.
In addition to the yield losses that larvae cause, feeding on mycelium, the mushrooms lose their marketable appearance because of the larvae that swarm on their surface. Larvae also enter fruit bodies forming many passageways and holes, which makes the mushrooms unsuitable for use.
As a result of a severe fly infestation, during spawning or on spawn run, the compost is colonized by a great amount of larvae that develop and feed inside it and produce a great amount of fecal substances. As a result, the affected substrate areas turn into swampy masses with a foul odor in which mushroom mycelium will not be able to grow. The rotting areas of compost and decaying pins that have been damaged by larvae form a suitable environment for the reproduction of various kinds of mites. Mites get inside the growing room with the help of adult flies (one fly can carry up to 30 mites). Since mites are usually associated with bacterial diseases and Verticillium (dry bubble), their spreading can lead to undesirable transfer of these pathogenic microorganisms throughout the whole mushroom farm.
As mushroom flies move from diseased mushrooms to healthy ones, they spread various diseases
Adult flies themselves can carry Verticillium, along with the spores of competing and parasitic fungi. This way, flies cause more damage to the mushroom culture than their larvae, and if no control measures are taken, they will constantly promote the infection of new batches of substrate with various diseases.
Usually, the amount of flies increases at summer and fall. During this time, a massive Phorid fly reproduction and migration occurs. They are very active near sources of light, and hence, they can be a nuisance to pickers at work.
Contrary to Phorid flies, which are seasonal pests, Sciarids can remain on the farm all year round and this is one of the reasons they develop a resistance to insecticides. Adult flies can be stopped from entering the rooms for filling the compost and spawning, and also the growing rooms by using protective nets on ventilation openings and sealing the doors. A separate attention has to be paid to the protection of air ducts, especially at ejection of air, because they are the sources of smells that attract flies. Since female flies can enter through the smallest openings and cracks, the nets must have 16 openings in one cm. The presence of openings around the protective nets, in the doors and walls must be excluded. The amount of flies passing through these barriers must be recorded with the use of flypaper, which should be used everyday. Light traps can also be used.
The quality of used substrate plays an important role. According to various experiments, there’s an antagonism between mycelium and sciarid flies, well grown compost doesn’t attract female flies for oviposition, and a big amount of mycelium suppresses the development of larvae. In that way, intense mycelial growth suppresses the oviposition and the development of larvae. And conversely, poor compost, where mycelium hardly grows, will be a suitable substrate for the development of sciarids and other flies.
Newly spawned substrates have to be protected from flies for the first few days with aerosols, smoke and fine-dyspersated application of allowed pesticides. In some cases, in order to control flies, insecticides are added to the compost.
When using insecticides in the compost, it is very important to mix and distribute the compound evenly, because the effect of the insecticide basically depends on the mixing thoroughness. It’s important for the insecticide and the mycelium to be as far from each other as possible during the spawning process, because at close contact, the insecticide has an adverse effect on the subsequent mycelium growth and fruit body formation. Therefore, mycelium and insecticide shouldn’t be applied to the compost at the same time. Regardless of the compound’s formula, it should be applied to the compost before spawning. That will help escape the «covering» of the mycelium with an insecticide. The treatment of compost will provide protection only during spawn run. The absence of protection after the application of casing layer can lead to the infestation of the casing soil with parasites, and can therefore cause damage to the mycelium on the surface of compost and casing layer.
The materials used to prepare the casing soil, and prepared casing soil should be stored in a clean room; if any pests are present in the casing soil, it has to be treated with formalin or pasteurized with steam.
During and after the preparation of the casing soil, it is treated with diflubenzurone (dimilin) in order to control the larvae. When the compound is applied during the casing soil preparation, it should be mixed uniformly and the compound has to be spread throughout the whole mass of the casing layer. Generally, any compound is applied to the mixture in a dissolved state during the mixing of its contents. Dimilin can be also used to treat the casing soil right after it’s applied, trying to ensure the penetration of the chemical through the layer. It’s important to remember that dimilin doesn’t dissolve in water; therefore, it’s necessary to constantly shake solution while working with it. The recommended use of dimilin is 4g/l/m2.
After the casing soil is applied, the entrance of flies into the growing rooms should be controlled with aerosols, smoke and fine-dyspersated spraying of permetrin, dichlorvos and perefosmetil (anometrin, forbecide and dichlorvos).
Flies that appear during fruiting, can be controlled with smoke or spraying compounds that contain pyrethride, though the constant use of this substance can lead to the pests developing resistance.
It’s important to state that the control of flies during fruiting is merely a cosmetic surgery, if it’s carried out apart from the other measures. Therefore, any measure should be a part of a well thought-out and strictly followed pest control program. The larvae of some flies are easily spread throughout the farm, therefore, it is necessary to isolate the growing rooms using mats for footwear, that have been treated with a disinfectant. Necessarily disinfect the working instruments and use different working clothes in each growing room.
In the end of the cultivation cycle all larvae must be destroyed with steaming of compost and the growing rooms. During steaming it is important to reach necessary temperatures in the growing room, on the shelves or in the containers.
If steaming is impossible, the spent batches and growing rooms must be disinfected. All spent compost must be immediately removed from the farm. The empty growing rooms must be thoroughly washed with a disinfectant.