Occurrence Characteristics and Control Methods of Mushroom Gall Midge

I. Morphological Characteristics

The gall midge, also known as the small red maggot or mushroom gnat, has adults that resemble small mosquitoes, tiny and delicate, difficult to see with the naked eye. The head, thorax, and dorsal side of the body are dark brown, while the rest is grayish-brown or light orange. Larvae can hatch from eggs or be reproduced by the mother's larvae. Each female can produce an average of more than 20 larvae. In the early stage, larvae cause damage in the substrate, resulting in sparse and weak mycelium. In the later stage, they move to the mycelium and fruiting bodies. When fruiting bodies are damaged, they first breed at the base of the mushroom stipe, then climb to the junction between the stipe and the cap, and some bore into the gills, which are eaten into scars and trails, appearing light orange-red. A single mushroom can host 20 to 30 larvae in severe cases, seriously affecting the quality and yield of mushrooms.

II. Causes of Occurrence

1. Improper composting of the substrate The pre-fermentation of the substrate is not thorough, the inner and outer piles are not turned evenly, the fermentation time is too short, and disinfection is inadequate. Although most substrates undergo "secondary fermentation" treatment, dead corners occur in the mushroom house during the heating phase, causing slow temperature rise or failure to reach the required temperature.

2. Unsuitable microclimate in the mushroom house The substrate itself is too wet when entering the mushroom house. During watering adjustment, if too much water is sprayed, the humidity inside the mushroom house becomes too high.

3. Poor cultivation environment Many mushroom growers use old mushroom racks that were not thoroughly disinfected after the previous year's harvest; the water source is not clean and carries pests, diseases, and contaminating microorganisms; gall midge adults are strongly phototactic and easily fly into the vicinity of the mushroom house to reproduce; ventilation is poor; and tools carrying pests, diseases, and contaminating microorganisms are used, spreading contamination.

III. Control Measures

1. Site selection and mushroom house disinfection The mushroom production site must be chosen in a dry area near a clean water source. If mushroom beds are built indoors, disinfection inside the room should be strengthened. Use sulfur mixed with dichlorvos at 1:1 for fumigation, repeating the fumigation every 5 days. If old mushroom racks made of bamboo or wood are used, first soak them in water for several days, drain, sun-dry, move them into the mushroom house, and fumigate them together. Alternatively, soak them in a 2% sodium pentachlorophenate solution for disinfection, which has a very good effect.

2. Maintain good environmental hygiene inside and outside the mushroom yard Promptly remove waste materials, dirt, and decaying matter; regularly spray disinfectants and insecticides such as dichlorvos on the cultivation site. Install screen doors and screen windows in the fruiting house, and use yellow sticky fly tape in combination to effectively block insect sources from entering and control adult insects from outside entering the mushroom yard.

3. The substrate must undergo "secondary fermentation" During the pre-fermentation process, turn the material evenly and control the moisture content of the substrate. During secondary fermentation, pay attention to the temperature and time during the heating and temperature-control phases to achieve the purpose of "secondary fermentation." Before secondary fermentation begins, put used or soon-to-be-used tools into the room for disinfection together to prevent contamination by pests, diseases, and contaminating microorganisms.

4. After inoculation of the mushroom bag, sealing is best done using the ring-cover sealing method. The sealing paper should be double-layered newspaper or book paper. During transport, prevent the sealing paper from falling off, and handle gently to avoid bag breakage. If breaks or puncture holes are found in the mushroom bag, immediately cover them with adhesive tape to prevent pests from laying eggs and causing damage at the openings.

5. Control the temperature and humidity of the mushroom house In mushroom production, the early stage often encounters relatively high temperatures. Doors and windows should be opened promptly, and water should be sprayed on the floor and in the air of the mushroom house. Effective ventilation of the mushroom house should be carried out to regulate the temperature and humidity suitable for mushroom growth and prevent temperature rise and excessive humidity inside the house.

6. Chemical control When turning the substrate pile, spray and mix the material with 90% trichlorfon or 50% malathion emulsion at a 1:1000 dilution, which can effectively prevent pest occurrence. It can also be sprayed on the bed surface when pest damage occurs. Alternatively, fumigate with a 1:1 mixture of formaldehyde and dichlorvos at 10 mL per cubic meter, or spray with 50% phoxim emulsion at a 1:800 to 1:1000 dilution.