Control Methods for Mushroom Pests in Autumn and Winter
Types and Identification of Pest Outbreaks
1. Mushroom gnats and mushroom flies: Autumn cultivation generally uses fermented substrate, such as oyster mushrooms, shaggy mane mushrooms, and button mushrooms. Small-bodied mushroom gnats, oyster mushroom sciarid flies, mushroom sciarid flies, spinous sciarid flies, heterogeneous sciarid flies, dung flies, phorid flies, fruit flies and other adults lay eggs near the substrate. Adults and eggs do not directly cause damage; when the temperature is between 16°C and 30°C, eggs hatch into larvae in about 4 days. Larvae feed on mycelium or fruiting bodies, cause damage for about 7 to 18 days, then pupate. The pupal stage generally lasts about 2 to 8 days, after which they emerge as adults. After emergence, adults can mate again on the same day or the next day, and can lay eggs on the day of mating. Generally, each mushroom gnat lays more than 10 eggs, with the maximum reaching 270 eggs. Adult mushroom gnats are relatively large; for common varieties, body length can exceed 3.5 mm, with the largest exceeding 6 mm. Larvae are generally about 5 mm long, with the largest exceeding 16 mm. Mushroom flies are smaller; the largest phorid fly adults are only about 1.5 mm long, while larvae are between 2 mm and 3 mm. However, fruit fly adults and larvae can reach about 5 mm in length, similar to mushroom gnats.
The adults of the above pests are strongly phototactic and odor-attracted (to mushroom aroma, substrate aroma, and decay odors). When the mushroom shed is kept dark, the occurrence probability is relatively low and pest population density drops greatly. Their larvae initially move within the surface layer of the substrate, biting and eating mycelium. After mushrooms emerge, they can bore to the base of the stipe and even up to the cap. After the mushroom body becomes "hollow," they return to the substrate and continue deeper damage until all mycelium in the substrate has been consumed.
2. Mites: Mites have many sources. They may live in cracks in the corners of the shed, survive in gaps between posts, cracks in racks and bamboo or wood, or enter the mushroom shed through various tools. Some can also be spread through spawn (mainly third-generation spawn). In short, there are many entry routes. Mites mainly cause damage by biting and eating mycelium, but when population density is high, they can also bite mushroom buds and mature fruiting bodies. The main mite species include flour mites, straw itch mites, and ear mites. Mites are extremely small, but they have gregarious habits, moving in piles and clusters on the substrate surface, in shed corners, and on the ground. When population density is very high, the substrate surface appears white (grayish-white), flesh-red, or even reddish-brown.
Mites reproduce extremely quickly. At 20°C to 30°C, completing one generation takes about 8 days, while some species require only 3 days to complete one generation. Depending on the species, some mites go through egg, larva, nymph, and adult stages, but some species only have egg and mite stages, because their eggs can develop directly into adults within the mother's body and then emerge by breaking out. When survival conditions are unsuitable, or when there is no mycelium or mushroom available for food, they can attach to tools, human bodies, or even other living insects, thereby moving to suitable places and continuing to survive and reproduce.
3. Springtails: These pests mostly cause damage in summer and autumn. They can survive at temperatures above 15°C and become increasingly active when the temperature reaches 22°C, reproducing and expanding accordingly. Springtails damage mycelium and fruiting bodies and hide in gills and small cracks, greatly reducing product value or even making it unsellable. There are many springtail species; common ones mainly include angular springtails, black angular springtails, and black flat springtails. Springtails have a long lifespan; most species can survive about half a year, and some as long as one year. Their main physical feature is their tiny body, generally about 1.5 mm, with the largest under 5 mm. The humid environment, dim light, and abundant mycelium and mushroom nutrients in mushroom sheds provide the best conditions for springtails to breed and multiply, so their harmfulness is relatively great.
4. Nematodes: Nematodes mainly harm mushroom mycelium. There are also multiple species, mainly stylet-bearing mycelial nematodes and stylet-less rhabditid nematodes. The former insert their stylets into mycelium to suck mycelial juices, causing mycelial growth to be blocked and then shrivel and die, producing a phenomenon of "mycelial retreat"; the latter rapidly stir mycelium with their heads, breaking it into extremely fine fragments, then swallow or suck them, also resulting in the disappearance of mycelium. Nematodes are tiny, generally about 1 mm, but they reproduce very quickly. Generally, at 20°C to 30°C, after mating, they can lay eggs in about 30 hours. One female can lay dozens of eggs, with the maximum reaching 140 eggs; development from egg to adult requires only about ten-plus days, and at temperatures above 25°C only about 8 days. Nematodes have smooth body surfaces and prefer water-soaked environments or conditions with high moisture. When moving, they appear like a mass of water moving, which is an important method for identifying nematodes.
Autumn production also has other pests or small animals that can cause a certain degree of damage, such as snails, woodlice, and mole crickets.
Preventing Pest Damage
Preventing pest damage is a proactive attitude in pest control during mushroom production, and the effect is excellent. The main measures include:
Substrate composting stage: First, using insect-proof nets to prevent pests from approaching the substrate to lay eggs is an economical, effective, and simple top-quality measure, while also effectively solving the problem of pesticide residues. Ordinary insect-proof nets used in vegetable breeding can be used; even tiny mushroom flies cannot get through. Second, frequently spray efficient, low-residue pesticides on the substrate surface to repel pests, but the concentration used should be low and the spray volume small to avoid pesticide residues. Third, when conditions permit, use sterilized substrate cultivation methods as much as possible, which prevents pests while also eliminating contaminating microbes and pathogens, achieving multiple benefits at once. Finally, in the cultivation of button mushrooms and Agaricus blazei, promote and apply secondary fermentation technology. Temperatures as high as above 60°C, lasting about 2 days, will kill all living pests including eggs, larvae, and adults. Although production costs increase slightly, it brings many effects: killing pests, killing (or inhibiting) microbes, uniform substrate decomposition, and removing odors, achieving multiple benefits at once.
Spawn running stage: A considerable number of pest infestations invade at this stage. The spawn running stage generally lasts about 3 to 5 weeks. Mushroom bags for oyster mushrooms, shaggy mane mushrooms, and others are all perforated with micropores, which can fully satisfy the entry and exit of mushroom gnats and mites with basically no restriction. First, seal the doors, windows, and ventilation openings of the spawn running room with high-density window screens (insect-proof nets are sufficient), and insist on dark cultivation to prevent adults from entering due to phototaxis. Second, frequently check whether there are adults indoors. Once found, immediately spray low-concentration pyrethroid pesticides to kill them. Even spraying plain water alone can make water droplets stick to the wings of mushroom gnats, causing adults to fall to the ground and be unable to fly again, which can also kill them. Finally, when the surrounding environment of the culture room is poor, for example near garbage, barns or toilets, or manure piles, besides cleaning and preventing as much as possible, frequently spraying insecticidal pesticides in the indoor space and on walls is also one of the very powerful preventive measures.
Fruiting management stage: First, seal the doors, windows, and ventilation openings of the mushroom shed with high-density window screens (insect-proof nets are sufficient) to prevent adults from entering. Second, reduce light inside the shed as much as possible. Third, insist on using well water or tap water for management water, not "dead water" from ditches, bays, or ponds. Fourth, spread a 1 m to 2 m wide lime belt on the ground at entrances and exits to prevent mites, woodlice, and other pests and small animals from entering. Finally, during the interval between fruiting flushes, spray an appropriate amount of pyrethroid pesticides, combined with formaldehyde and bleaching powder pesticides, which has the dual effect of preventing both pests and microbes. However, during the growth of fruiting bodies, any pesticides should be prohibited to prevent residues from affecting quality.
Sources of Pests
In mushroom cultivation production, most pests enter the substrate in the form of eggs. A small portion lay eggs in the substrate before spawning, while most lay eggs after spawning. The probability of entering the spawning stage through spawn carrying live larvae (or live pests) is relatively small. Egg hatching and substrate spawn running proceed simultaneously, and under normal circumstances they simply cannot be found or identified with the naked eye; at first, both individual larvae and larval groups are small, and the amount of mycelium they eat is very small, so it is not easy to attract attention. By the time the larvae continue to develop and grow, and as the population expands and damage to mycelium becomes more serious, it is already the first fruiting flush or the peak fruiting period. At this stage it is still difficult to detect, until the second fruiting flush becomes difficult, or even no more mushrooms are produced, and the mycelium on the substrate surface has almost disappeared and turned brown, only then is it discovered that pests were the culprit. It can be said that a considerable number of producers discover pests at this stage. Another characteristic of pests in autumn and winter is that as the temperature gradually decreases, pests are also looking for warm shelters. The inside of the substrate is relatively suitable, and the temperature in culture rooms and cultivation sheds is also relatively suitable. After finding a suitable "residence," they reproduce rapidly, causing the pest population to expand rapidly.
Damage Symptoms
For pests occurring on mushrooms, during the early spawn running stage they all live by biting and eating mycelium, and during the later fruiting stage they "eat everything," including fruiting bodies. When infestation is severe, the substrate surface changes from white to yellow, to brown, or even black. The surface layer and even the interior are densely covered with pest excrement. The base of the fruiting body and even the entire stipe are eaten into a sponge-like state, and there are even insect holes on the caps.
On the other hand, pest damage can lead to the rampant spread of certain diseases or contaminating microbes. For example, mycelium on the substrate surface disappears and pest excrement is everywhere. After causing rot, contaminating microbes such as Trichoderma and Rhizopus take the opportunity to invade, easily producing disease; pests biting fruiting bodies cause young mushrooms (mushroom buds) to die and rot, and can also easily attract outside adults to enter. Pest bodies carry various bacteria or fungi, and while increasing pest (population) density, they also bring in a large number of pathogens, making already damaged mushroom production "worse."
Methods for Killing Pests
To discover pests in time and take measures to kill them, pesticide varieties should be strictly selected, paying attention both to the problem of pesticide residues and to preventing phytotoxicity.
When pest density is extremely low at the initial stage, use efficient, low-residue pyrethroid pesticides and spray in the air or on the substrate surface casing soil to kill them.
When occurrence is moderate, some eggs will be laid in the substrate. The fruiting bodies can be harvested all at once. For mushroom gnats and springtails, spray 800-fold DDV on the substrate surface and casing soil layer, and cover with plastic film for 3 to 5 hours; for mite pests, spray 1000-fold acaricides, such as saomante and shamandol, also covering with plastic film for several hours; for nematodes, use 0.5% formaldehyde solution for heavy spraying, also covering with plastic film for 2 to 4 hours.
When brown patches appear on the substrate surface and there is insect boring on the stipes, it is already a severe outbreak. At this time, larvae are mostly within the substrate, and spraying pesticides is generally ineffective. Aluminum phosphide "total kill" measures can be used to kill them all at once. The method is: harvest all fruiting bodies. For wall cultivation, cover the mushroom wall with plastic film, place one piece of aluminum phosphide every 1 m on both sides, quickly compact the edges of the plastic film with soil, and about 8 to 10 hours is sufficient. For bed cultivation, refer to the above for pest killing. Key points to note: operate quickly; compact the film well; when removing the film, first open the mushroom shed doors, windows, and ventilation openings. Then lift the plastic film, and after 1 to 2 hours, move the plastic film outside the shed, carefully pick out the aluminum phosphide waste, and bury it deeply. Do not discard it carelessly.