How to control mites in oyster mushroom cultivation during the hot season?

I. Main pest mites

1. Tyrophagus putrescentiae (mold mite)

Distribution and damage: This mite is a cosmopolitan species. In edible mushroom production, mold mites often occur in environments contaminated by weed molds; through their activity they spread the weed molds, causing healthy fruiting bodies to be damaged and rot. Mold mites can also feed directly on the mycelium of oyster mushrooms, causing reduced yields or even total crop loss.

Morphological characteristics: Adult male mites are 240-320 micrometers long, adult females 350-650 micrometers long; the body is colorless, the chelicerae and legs are pale yellow to reddish-brown, and the posterior end is bluntly rounded. The legs are relatively thick, divided into 6 segments.

Habits: Tyrophagus putrescentiae often enters the mushroom house with compost that has not undergone high-temperature fermentation or thorough disinfection, or is carried to the mushroom beds by insects, wind, tools, and other means. After edible mushrooms are inoculated, if weed mold contamination occurs, the mites quickly gather and become active in areas with abundant mold. Under suitable temperature and high humidity, they reproduce rapidly; at a temperature of 23°C and humidity of 87%, they can complete one generation in only 9-11 days. When populations are large, large amounts of shed skins and excrement remain on the compost or mycelium, giving off a musty odor. Tyrophagus putrescentiae has strong cold resistance, but its drought tolerance is very poor; eggs can hardly hatch at all under 60% relative humidity, and in dry environments a dormant stage can form between the first and second nymphal instars. The spread of this mite in mushroom houses or on mushroom beds occurs not only through its own crawling, but mainly by attaching to other pests and mites.

2. Tyrophagus putrescentiae (cheese mite)

Distribution and damage: This mite is a cosmopolitan pest mite and is widely distributed in China. It often occurs mixed with Tyrophagus putrescentiae, damaging fungal substances. Affected stored materials often carry a foul odor. In addition, materials carrying Tyrophagus putrescentiae can cause rash disease if eaten by humans, and skin contact with this mite can sometimes cause dermatitis.

Morphological characteristics: Adult male mites are 280-350 micrometers long, with a smooth, glossy cuticle; adult females are 320-415 micrometers long, with body shape, setae length, and arrangement similar to males; larvae are milky white with 3 pairs of legs; nymphs are milky white with 4 pairs of legs and can be divided into the first nymphal stage and the second nymphal stage.

Habits: As long as environmental conditions are suitable, they can grow, develop, and reproduce throughout the year. In China, the peak occurrence period for mites is during the plum rain season. This mite moves quickly, prefers to be active in dark places, often gathers on surfaces to cause damage, likes moisture and fears dryness; eggs require relative humidity above 70% to hatch.

II. Occurrence patterns

1. Causes of pest mite occurrence: Oyster mushroom houses are close to warehouses, feed rooms, chicken coops, and storage areas for coarse bran, cottonseed hulls, rapeseed cake, etc., or mites are brought to the mushroom beds by insects and other means; during disinfection of empty rooms, mites and their eggs hidden in cracks are not killed; spawn carrying pest mites; compost carrying pest mites that is not thoroughly treated; casing soil is not disinfected and contains pest mites.

2. Damage symptoms: In spawn affected by mite damage, the mycelium at the bottle mouth is not dense enough and shrinks and degenerates, and sometimes no mycelium can be seen in the culture medium at all. When oyster mushrooms are damaged by pest mites during the mycelial growth phase, the white mycelial blocks turn black and give off an unpleasant musty odor. When young mushrooms or mature fruiting bodies are damaged, brown or yellow spots of varying shapes appear on the caps or stipes; in the early stage, the spots are sunken or form holes, with dark brown edges and slightly lighter centers or hollow centers, but the fruiting bodies do not rot.

III. Control methods

1. Disinfection of the culture room, mushroom house, and compost: The mushroom house should be fitted with fine-mesh screen doors and windows, and ventilation openings should also be fitted with screen mesh. Cracks around the walls of the house should be sealed tightly with mud to prevent insects from flying in and bringing mites to the mushroom beds. The spawn culture room should be built far away from livestock sheds, poultry houses, and warehouses. Stacking sawdust, cotton hulls, and other compost materials and miscellaneous items indoors is strictly prohibited; the culture room and mushroom house should be disinfected regularly, spraying the surrounding walls, floor, and cultivation racks with chemicals to eliminate mites and insect pests. The compost should undergo two fermentation cycles or high-temperature disinfection to kill pest mites in the material. Maintain good environmental hygiene to reduce weed mold contamination and thereby reduce mite infestation damage.

2. Ensure spawn is absolutely mite-free: Carefully inspect the spawn; if mites are found in spawn bottles, they must be discarded; or spawn suspected of having mites should be inoculated in a separate room.

3. Chemical mite control: When pest mite damage is found on mushroom beds, chemical sprays can be used, namely propargite 2000-fold solution or lime-sulfur mixture at 0.5-1.0 degrees Baume. Trapping can also be used: fresh tobacco leaves can be laid flat on the surface of the compost where mites are causing damage; when many mites have gathered on the tobacco leaves, gently remove the leaves and burn them. If mites are still found, repeat as before until no mites remain. Alternatively, take 10 milliliters of boiling water, 100 milliliters of vinegar, and 10 grams of white sugar, mix well, stir until dissolved, and after cooling, add one drop of dichlorvos and mix well to make a sugar-vinegar solution. Soak gauze in the prepared sugar-vinegar solution until thoroughly wet, then lay it on the compost or mushroom bed where mites are causing damage. After the mites are attracted onto the gauze, remove the gauze and scald the mites to death with boiling water; repeat multiple times until the mites are basically killed.