Pest Control Methods for Edible Mushrooms in Autumn and Winter
Recently there have been many inquiries about pest problems in autumn-cultivated edible mushrooms. Field research has found that pest damage in edible mushrooms was relatively severe this autumn. Some mushroom sheds had almost become "pest sheds," and the pest damage triggered massive contamination by weed molds and serious diseases, causing heavy losses for mushroom growers. Today, based on the research findings, we have invited experts to explain the "prevention" and "treatment" of pests in autumn and winter to fellow mushroom growers, in order to reduce their losses.
Types of pest outbreaks and their identification
1. Mushroom gnats and mushroom flies: Autumn cultivation generally uses fermented substrate, such as oyster mushrooms, shaggy mane mushrooms, and button mushrooms. The smaller mushroom gnats, oyster mushroom eye gnats, mushroom eye gnats, spinous eye gnats, heterogeneous eye gnats, dung flies, phorid flies, fruit flies, and other adults lay eggs near the substrate. The adults and eggs themselves do not cause direct harm; when the temperature is between 16°C and 30°C, the 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, with most species having a body length of more than 3.5 mm, and the largest can exceed 6 mm. Larvae generally have a body length of about 5 mm, with the largest exceeding 16 mm. Mushroom flies are smaller in size, with the largest phorid fly adults having 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-attracted (to mushroom aroma, substrate aroma, and decay odors). When the mushroom shed is kept dark, the probability of occurrence is relatively low, and pest population density drops greatly. The larvae initially all move about in the surface layer of the substrate, biting and eating the mycelium. After fruiting begins, they can bore down to the base of the stipe and 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 live in crevices in the corners of the shed, can survive in cracks in posts, frame poles, bamboo, and wood, and can also enter the mushroom shed through various tools. Some can also be spread through spawn (mainly third-generation spawn). In short, there are many routes of entry. Mites cause damage mainly by biting and eating mycelium, but when population density is high, they can also bite and gnaw mushroom buds and mature fruiting bodies. The main mite species include flour mites, straw itch mites, and tarsonemid mites. Mites are extremely small, but they have gregarious habits, moving in heaps and clusters on the substrate surface, in the corners of the shed, and on the ground. When population density is very high, the substrate surface appears white (grayish-white) or flesh-red, even reddish-brown.
Mites reproduce extremely quickly. At temperatures of 20°C to 30°C, completing one generation requires about 8 days, while some species need only 3 days to complete one generation. Depending on the species, some mites also go through egg, larval mite, nymph, and adult mite stages, but some species have only eggs and mites, because their eggs can develop directly into adult mites inside the mother's body and then emerge by breaking out. When survival conditions are unsuitable, or when there are no mycelia or mushrooms to eat, they can attach to tools, human bodies, or even the living bodies of other insects, taking the opportunity to move to suitable places and continue their survival and reproduction and expansion.
3. Springtails: These pests cause damage mostly in summer and autumn. They can survive at temperatures above 15°C, gradually become active when the temperature reaches 22°C, and then reproduce and expand. Springtails damage mycelium and fruiting bodies, and hide in the gills and tiny crevices, greatly reducing product value or even making it worthless. There are many species of springtails, with the common ones mainly including horned springtails, black-horned springtails, and black flat springtails. Springtails have very long lifespans; most species can live about half a year, and the longer-lived ones reach one year. The main physical characteristics of springtails are their tiny bodies, 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 thrive and reproduce, so their harmfulness is relatively great.
4. Nematodes: Nematodes mainly harm edible mushroom mycelium. There are also many species, mainly including stylet-bearing mycelial nematodes and stylet-less rhabditid nematodes. The former insert their stylets into the mycelium to suck out mycelial fluids, causing mycelial growth to be blocked and then to shrink and die, producing a "mycelial regression" phenomenon. The latter rapidly stir the mycelium with their heads, breaking it into extremely fine mycelial fragments, and then swallow or suck them, also resulting in the disappearance of the 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 several dozen eggs, with the maximum reaching 140 eggs. From egg to adult takes only a little over ten days, and at temperatures above 25°C it takes only about 8 days. Nematodes have smooth body surfaces and prefer water-soaked environments or conditions with relatively high moisture. When moving, they look like a mass of water moving, which is an important way to identify 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 is a proactive approach to pest control in edible mushroom production, and the results are excellent. The main measures are: During the substrate fermentation stage: First, using insect-proof netting to prevent insects from laying eggs near the substrate is an economical, effective, and simple top-quality measure, and it also effectively solves the problem of pesticide residues. Ordinary insect-proof netting used in vegetable breeding is sufficient; even tiny mushroom flies cannot get through. Second, frequently spray high-efficiency, low-residue pesticides on the substrate surface to repel insects, but the concentration used should be low and the amount sprayed should be small, so as to avoid pesticide residues. Third, when conditions permit, use sterilized substrate cultivation methods as much as possible, which while preventing insects also eliminates weed molds and pathogens, achieving multiple benefits at once. Finally, in the cultivation of button mushrooms and Himematsutake, promote and apply the secondary fermentation technique. Temperatures as high as above 60°C, lasting about 2 days, will kill all live insects including eggs, larvae, and adults. Although production costs increase slightly, it brings many effects in return: killing insects, killing (or inhibiting) microbes, evenly composting the substrate, and removing off-odors, truly achieving multiple benefits at once.
Spawn running stage: A considerable number of pests invade during 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 allow mushroom gnats and mites to enter and exit with basically no restriction. First, seal the doors, windows, and ventilation openings of the spawn running room with high-density window screening (such as insect-proof netting), and insist on culturing in darkness 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 the 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, stables and latrines, or manure piles, in addition to cleaning and preventing as much as possible, it is also a very powerful preventive measure to frequently spray insecticidal pesticides in the indoor space and on the walls. Fruiting management stage: First, seal the doors, windows, and ventilation openings of the mushroom shed with high-density window screening (insect-proof netting is 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, not "dead water" from ditches, ponds, or pools. 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 the application of formaldehyde and bleaching powder types of agents, which has the dual effect of preventing both insects and microbes. 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 and production, most pests enter the substrate in the form of eggs. A small portion lay eggs in the substrate and then spawn is inoculated, while most lay eggs after spawning. The probability of entering the spawning stage through live larvae (or live insects) carried by spawn is relatively small. Egg hatching proceeds in sync with substrate colonization, and under normal circumstances it simply cannot be detected or identified with the naked eye. At first, both individual larvae and their populations are small, and the amount of mycelium they eat is very small, so it is not easy to notice. By the time the larvae continue to develop and grow, and as the population expands and damage to the 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. Only when 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, does one discover that pests were the culprits. 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 temperatures gradually decrease, insects are also looking for warm shelters. The inside of the substrate is relatively suitable, and the temperatures in culture rooms and cultivation sheds are also relatively suitable. After finding a suitable "lodging," they reproduce rapidly, causing the pest population to expand sharply.
Damage symptoms: Pests occurring on edible mushrooms all feed on mycelium during the early spawn running stage. In the later fruiting stage, they "eat everything," including the fruiting bodies. When outbreaks are severe, the substrate surface changes from white to yellow, to brown, and even to 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 weed molds. For example, when mycelium disappears from the substrate surface and pest excrement is everywhere, after causing rot, weed molds such as Trichoderma and Rhizopus take the opportunity to invade, easily causing disease. Insects biting and eating fruiting bodies causes young mushrooms (mushroom buds) to die and rot, and also easily attracts outside adults to enter. The insect bodies carry numerous bacteria or fungi, which while increasing pest (population) density also bring in large amounts of pathogens, making an already damaged edible mushroom production situation "even worse."
Methods for killing pests: Timely discovery of pest damage and taking measures to kill pests require strict selection of pesticide varieties, paying attention both to pesticide residue issues and preventing phytotoxicity. When pest density is extremely low at the initial stage, use high-efficiency, low-residue pyrethroid pesticides and spray in the air or on the casing soil surface to kill them.
When occurrence is moderate, some eggs will have been laid in the substrate. The fruiting bodies can be harvested all at once. For mushroom gnats and springtails, spray 800x DDV on the substrate surface and casing soil layer, and cover with plastic film for 3 to 5 hours. For mite pests, spray 1000x acaricides, such as saomante and fenazaquin, also covering with film for several hours. For nematodes, use 0.5% formaldehyde solution for heavy spraying, also covering with film for 2 to 4 hours.
When brown patches appear on the substrate surface and there is insect boring on the stipes, it has reached a severe occurrence level. At this time, the larvae are mostly in the substrate, and spraying pesticides is generally ineffective. Phosphine fumigation can be used as a "total kill" measure to eliminate them all at once. The method is: harvest all fruiting bodies. For wall cultivation, cover the mushroom wall with plastic film, place one phosphine tablet every 1 m on both sides, quickly press the edges of the plastic film firmly with soil, and about 8 to 10 hours is sufficient. For pest killing in bed cultivation, refer to the above. Key points to note: operate quickly; press the film firmly; when removing the film, first open the mushroom shed doors, windows, and ventilation openings. Then lift the plastic film. After 1 to 2 hours, move the plastic film out of the shed, carefully pick out the phosphine waste material, and bury it deeply. Do not discard it randomly.