As temperatures rise, oyster mushroom mite control must be carried out promptly

In recent years, when mushroom growers cultivate oyster mushrooms in spring and early summer, much of the raw material used is left over from last year and often carries mites. Mites feed on oyster mushroom mycelium and fruiting bodies, causing reduced yields and, in severe cases, total crop failure. At present, temperatures are gradually rising, which is very suitable for mite growth and development and accelerates their reproduction, so growers should pay attention to control.

I. Main pest mites

1. Acarus siro

Distribution and damage: This mite is a worldwide species. In edible mushroom production, flour mites often occur in environments contaminated by competing microorganisms; through their activity they spread the contaminants, causing healthy fruiting bodies to become damaged and rot. Flour mites can also directly feed on oyster mushroom mycelium, causing reduced yields or even total crop failure.

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 and consist of 6 segments in total.

Habits: Acarus siro often enters mushroom houses along with culture material that has not undergone high-temperature fermentation or thorough disinfection, or is brought to the mushroom beds by insect vectors, wind, tools, and so on. After edible mushrooms are inoculated, if competing microorganism contamination appears, they rapidly gather and become active in areas with more mold. Under suitable temperature and high humidity, they reproduce quickly; at a temperature of 23°C and humidity of 87%, they need only 9-11 days to complete one generation. When populations are large, large amounts of shed skins and excrement remain on the culture material or mycelium, giving off a musty odor. Acarus siro has strong cold resistance, but its drought tolerance is very poor; eggs can almost completely fail to hatch at a relative humidity of 60%, and in dry environments a dormant form can develop between the first and second nymphal stages. In mushroom houses or on mushroom beds, this mite spreads not only by crawling itself, but mainly by attaching to other pests and mites.

2. Tyrophagus putrescentiae (mold mite)

Distribution and damage: This mite is a worldwide pest mite and is commonly distributed in China. It often occurs mixed with Acarus siro and damages fungal materials. Affected stored materials often carry a foul odor. In addition, after materials carrying Tyrophagus putrescentiae are eaten by people, they can cause rash disease, and when human skin comes into contact with this mite, dermatitis sometimes occurs.

Morphological characteristics: Adult male mites are 280-350 micrometers long, with a smooth, glossy cuticle; adult females are 320-415 micrometers long, and their body shape, bristle length, and arrangement are similar to those of 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 of these mites is during the plum rain season. This mite moves quickly, likes to be active in dark places, often gathers on surfaces to cause damage, and prefers moisture while fearing dryness; eggs can hatch only at a relative humidity above 70%.

II. Occurrence patterns

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

2. Damage symptoms: In spawn affected by mites, the mycelium at the bottle mouth is not dense enough and shrinks and degenerates, and in severe cases no mycelium can be seen in the culture medium. When oyster mushrooms are affected by pest mites during the mycelial growth stage, 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 become 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 culture rooms, mushroom houses, and culture material: Mushroom houses should be fitted with fine-mesh screen doors and screen windows, and ventilation holes should also be fitted with screen mesh. Cracks around the house body should be sealed tightly with mud to prevent insects from flying in and bringing mites to the mushroom beds. Spawn culture rooms should be built away from livestock sheds, poultry houses, and warehouses, and it is strictly forbidden to pile up culture materials such as sawdust and cottonseed hulls and miscellaneous items indoors; culture rooms and mushroom houses should be disinfected frequently, and pesticides should be sprayed around the house, on the ground, and on cultivation racks to eliminate mites and insect pests. Culture material should undergo secondary fermentation or high-temperature disinfection to kill pest mites in the material. Maintain good environmental sanitation and reduce contamination by competing microorganisms to reduce mite infestation and damage.

2. Ensure spawn is absolutely mite-free: Carefully inspect spawn; if mites are found in spawn bottles, discard them; or spawn suspected of containing mites should be inoculated in separate rooms.

3. Chemical mite elimination: When pest mite damage is found on mushroom beds, spraying with chemicals can be used: propargite 2000-fold solution, or lime sulfur mixture at 0.5-1.0 degrees Baumé. Trapping and killing can also be used: spread fresh tobacco leaves flat on the surface of culture material damaged by mushroom mites, and when many mushroom mites have gathered on the tobacco leaves, gently remove the tobacco leaves and burn them; if mites are still found, continue as before until there are no more mites. 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 sugar-vinegar liquid. Soak gauze in the prepared sugar-vinegar liquid until thoroughly wet, then spread it on the culture material or mushroom bed damaged by mites. After attracting the mites onto the gauze, remove the gauze and scald the mites to death with boiling water. Repeat many times until the mites are basically killed.