Methods and Techniques for Pest Control in Winter Edible Mushroom Cultivation
Recently there have been many inquiries about pest problems in autumn-cultivated edible mushrooms. Field investigations have found that this autumn the pest problems in edible mushrooms are relatively severe, with some mushroom sheds almost becoming "pest sheds," and the pest damage has triggered a large amount of weed mold contamination and serious diseases, causing heavy losses for mushroom growers. Today we have invited experts, based on the investigation results, to introduce to mushroom grower friends the "prevention" and "treatment" of pests in autumn and winter, in order to reduce losses for mushroom growers.
Types of pest occurrence and identification
1. Mushroom gnats and mushroom flies: Autumn cultivation generally uses fermented substrate, such as oyster mushrooms, king oyster mushrooms (shimeji), and button mushrooms, etc. The smaller-bodied mushroom gnats, oyster mushroom eye gnats, mushroom eye gnats, spiny eye gnats, heterogeneous eye gnats, dung flies, phorid flies, fruit flies, and other adults lay eggs near the substrate; the adults and eggs cannot directly cause harm. When the temperature is between 16°C and 30°C, eggs hatch into larvae in about 4 days. The larvae feed on mycelium or fruiting bodies, causing damage for about 7 to 18 days before pupating. 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. Mushroom gnat adults are relatively large in body size; generally the body length of common species can be over 3.5 mm, with the largest exceeding 6 mm. Larvae are generally about 5 mm in body length, with the largest exceeding 16 mm. Mushroom flies are relatively small in body size; the largest phorid flies have adults with a body length of only about 1.5 mm, and larvae between 2 mm and 3 mm. However, fruit fly adults and their larvae can reach about 5 mm in body length, similar to mushroom gnats.
The adults of the above pests are highly phototactic and odor-tropic (attracted to mushroom aroma, substrate aroma, and decay odors). When the mushroom shed is kept dark, the probability of occurrence is relatively low, and the pest population density drops greatly. Their larvae initially all move within the surface layer of the substrate, biting and feeding on 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 to cause damage deeper in, until they have completely consumed all the mycelium in the substrate.
2. Mites: Mites have many sources. They may reside in cracks in the corners of the shed, or survive in gaps between posts, cracks in wooden and bamboo poles. They can also enter the mushroom shed through various tools, and some can be spread through spawn (mainly third-generation spawn). In short, there are many entry routes. Mites mainly cause damage by biting and feeding on mycelium, but when the pest population density is high, they can also bite and feed on mushroom buds and mature fruiting bodies. The main mite species include flour mites, pyemotid mites, and tarsonemid mites. Mites are extremely small individually, but they have gregarious habits, moving in piles and clumps on the substrate surface and in the corners and on the ground of the mushroom shed. When the pest population density is very high, the substrate surface appears white (grayish-white) or flesh-red, even reddish-brown.
Mites reproduce extremely fast. At temperatures of 20°C to 30°C, completing one generation takes about 8 days, and 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 eggs and mites, because their eggs can develop directly into adults inside the mother's body, and then emerge by breaking out of the body. When living 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, and use the opportunity to transfer to suitable locations, continuing their survival and reproduction and expansion.
3. Springtails: These pests mostly cause damage in summer and autumn. They can survive at conditions above 15°C, and gradually become active when the temperature reaches 22°C, and subsequently reproduce and expand. Springtails feed on mycelium and fruiting bodies as their targets of damage, and lurk in the gills and tiny crevices, greatly reducing the value of the product or even making it worthless. There are many springtail species, with the common ones mainly including horned springtails, black-horned springtails, and black flat springtails. Springtails have a very long lifespan; most species can survive for about half a year, with the longest reaching one year. The main morphological characteristic of springtails is their tiny body size, generally about 1.5 mm, with the largest also under 5 mm. The humid environment, dim light, and abundant mycelium and mushroom nutrients in the mushroom shed provide the best conditions for springtails to reproduce and thrive, therefore their harmfulness is relatively great.
4. Nematodes: Nematodes mainly harm edible mushroom mycelium. There are also multiple species, mainly including myceliophagous nematodes with stylets and rhabditid nematodes without stylets. The former insert their stylets into the mycelium to suck out the mycelial fluid, causing mycelial growth to be hindered and then to shrink and die, producing a "mycelium regression" phenomenon. The latter use their heads to rapidly agitate the mycelium, breaking it into extremely fine mycelial fragments, and then swallow or suck them, with the result also being the disappearance of mycelium. Nematodes are tiny in body size, generally about 1 mm, but their reproduction speed is very fast. Generally at conditions of 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. From egg development to adult takes only about ten-plus days, and at conditions above 25°C it takes only about 8 days. Nematode pests have smooth body surfaces and prefer water-soaked environments or conditions with relatively high moisture. When moving, they appear like a mass of water moving, which is an important method for identifying nematodes.
In autumn production, there are also other pests or small animals that can cause a certain degree of damage, such as snails, woodlice, and mole crickets. Preventing pest damage is a proactive attitude toward pest control in edible mushroom production, and the effect is excellent. The main measures are: During the substrate fermentation stage: First, using insect-proof nets to prevent pests from laying eggs near the substrate is an economically effective, simple, and excellent measure, and at the same time effectively solves the problem of pesticide residues. Using ordinary insect-proof nets used in vegetable breeding is sufficient; 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 amount should be small, to avoid pesticide residues. Third, when conditions permit, try to use sterilized substrate cultivation methods, which prevents pests while also eliminating weed molds and pathogens, achieving multiple benefits at once. Finally, in the cultivation of button mushrooms and Agaricus blazei, promote and apply the secondary fermentation technique. 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 multiple effects including killing pests, killing (suppressing) bacteria, evenly decomposing the substrate, and removing odors, which can be described as 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. Spawn bags of oyster mushrooms, king oyster mushrooms, etc. 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 simply spraying clean water so that water droplets stick to the wings of mushroom gnats can cause 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, close to garbage, latrines, or manure piles, in addition to cleaning and preventing as much as possible, frequently spraying insecticidal pesticides in the space and on the walls indoors is also a very powerful preventive measure. During the 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 the light inside the shed as much as possible. Third, insist on using well water or tap water for management water, and do not use "dead water" from ditches, bays, or ponds. Fourth, spread a 1 m to 2 m wide lime strip on the ground at the entrance and exit to prevent mites, woodlice, and other pests and small animals from entering. Finally, during the intermission between fruiting flushes, spray an appropriate amount of pyrethroid pesticides, combined with the application of formaldehyde and bleaching powder pesticides, which has the dual effect of preventing both pests and bacteria. However, during the growth of fruiting bodies, any pesticides should be prohibited to prevent pesticide residues from affecting quality.
Sources of pests: In edible mushroom cultivation production, most pests enter the substrate in the form of eggs. A small portion lay eggs inside 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 proceeds simultaneously with substrate spawn running. Under general conditions, it is completely impossible to detect or identify with the naked eye. At first, the individual larvae and their populations are both small, and the amount of mycelium they feed on is very small, not easily attracting attention. By the time the larvae continuously develop and grow, and as the population expands, causing heavier damage to the mycelium, 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 completely 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 inside the culture room and cultivation shed is also relatively suitable. After finding a suitable "residence," they rapidly reproduce, causing the pest population to expand rapidly.
Damage symptoms: Pests occurring on edible mushrooms all feed on mycelium during the early spawn running stage, and during the later fruiting stage they "eat everything" including the fruiting bodies. When infestation is severe, the substrate surface turns from white to yellow, to brown, and even becomes 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 pest holes on the caps. On the other hand, pest damage can lead to the rampant spread of certain diseases or weed molds. For example, when the mycelium on the substrate surface disappears and pest excrement is everywhere, causing rotting, weed molds such as Trichoderma and Rhizopus take the opportunity to invade, easily producing diseases. Pests biting and feeding on fruiting bodies causes young mushrooms (mushroom buds) to die and rot, and also easily attracts external adults to enter. The pest bodies carry several bacteria or fungi, which while increasing the pest (population) density, also bring in a large amount of pathogens, adding "frost on top of snow" to the already damaged edible mushroom production.
Methods for killing pests: Timely discovery of pest damage and taking measures to kill them should strictly select pesticide varieties, paying attention to both the problem of pesticide residues and preventing pesticide damage. When the initial pest density is extremely small, using efficient low-residue pyrethroid pesticides, spraying in the air or on the casing soil surface of the substrate is sufficient to kill them.
When occurrence is moderate, some will lay eggs inside the substrate. The fruiting bodies can be harvested all at once. For mushroom gnats and springtails, use 800-fold DDV to spray the substrate surface and casing layer, and cover with plastic film for 3 to 5 hours. For mite pests, spray 1000-fold acaricides, such as fenbutatin oxide and dicofol, also covering with plastic film for several hours. For nematodes, use 0.5% formaldehyde solution for heavy spraying, also requiring covering with plastic film for 2 to 4 hours.
When brown patches appear on the substrate surface and there is pest boring damage on the stipes, it is already a severe occurrence. At this time, larvae are mostly inside 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 mushroom wall cultivation, use plastic film to cover the mushroom wall, placing one piece of aluminum phosphide at 1 m intervals on both sides, and quickly compact the soil around the plastic film, for about 8 to 10 hours. For mushroom bed cultivation, refer to the above for pest killing. Key points to note: operations must be fast; the film must be compacted; when removing the film, first open the doors, windows, and ventilation openings of the mushroom shed. 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 material, and bury it deep. Do not discard it randomly.