How to prevent and control pests and diseases of edible fungi? A detailed explanation of integrated control techniques

Edible fungi belong to the macrofungi, and the environmental conditions required for their growth and development are also suitable for the occurrence, growth and reproduction of many pests and diseases. If the control of the ecological environment is not taken seriously, and necessary preventive measures are not taken in the early stage, contaminant microorganisms and various insect pests will occur in large numbers. In cultivation, following the integrated control policy of giving priority to agricultural control, reasonably combining biological and physical methods, and using chemical control as a remedial measure, and giving full play to the complementary advantages of various control methods, will be of very great significance for achieving high quality and high yield of various edible fungi.

1 Common types of pests and diseases in edible fungus production

1.1 Brown rot disease. Also called bubble disease, wet bubble disease, etc. (Figure 1). It mainly harms button mushrooms, straw mushrooms, oyster mushrooms, etc. The disease is caused by the pathogen Mycogone perniciosa. Its main characteristics are: the conidia and chlamydospores of Mycogone perniciosa only infect the fruiting body, not the mycelium. When the fruiting body is lightly infected, the stipe swells into a bubbly malformation, hence the name wet bubble disease. However, at different developmental stages of the fruiting body, the symptoms also differ. When the fruiting body is infected before differentiation, there is an irregular tissue mass like a hard-skinned puffball, covered with a layer of white cottony mycelium, which gradually turns dark brown, and dark black droplets often seep from the diseased tissue; when infection occurs after the cap and stipe have differentiated, the stipe turns brown, and infection on the gills produces two kinds of white mycelial growths. The Mycogone perniciosa pathogen is a common soil fungus, and it is mainly transmitted to the casing bed and fungus blocks through casing soil, air, operators, tools, and carriers such as insects and mice.

1.2 Wilt disease. Also called dead wilt disease, it is a physiological disease. It mainly harms button mushrooms, oyster mushrooms, Phoenix mushrooms, Ling mushrooms, nameko mushrooms, etc. Its main characteristics are: after the mushroom buds form, fruiting bodies of various sizes can develop this disease. After onset, growth stops, they turn yellow, gradually shrink, soften, and dry out, and finally die or rot. The main causes are that after primordium formation the substrate is too dry, causing the mushroom buds to wilt; or the fruiting is too dense; insufficient nutrient supply, causing some small mushrooms to die; or the mushroom house temperature is too high, humidity is too high, ventilation is poor, oxygen is lacking, and the carbon dioxide content in the air is too high; and also accidental bruising of small mushroom buds during harvesting, or excessive fruiting, resulting in phytotoxicity.

1.3 Malformed mushroom disease. It is also a physiological disease. During the formation of fruiting bodies, if edible fungi encounter adverse environments and conditions that prevent the fruiting bodies from developing normally, malformations will occur (Figure 2). Its main characteristics are: small and thin caps, slender stipes, and early veil opening. This phenomenon occurs mostly after the first flush in oyster mushrooms and Phoenix mushrooms, while in shiitake it occurs in the first flush. Its main causes are high temperature, insufficient light, and nutrient deficiency.

1.4 Damping-off disease. Also called wilt disease, it is a fungal disease. It is mainly caused by Fusarium and Fusarium solani f. sp. phaseoli. The main symptom is that after the fruiting body is infected, the pith of the stipe shrinks and turns brown, and the mushroom body becomes short and stops growing. In the early stage of this disease, it is not easy to notice from the appearance compared with healthy mushrooms; only the cap becomes darker, the mushroom body stops growing, and finally it becomes a mummified mushroom. Transmission routes: because Fusarium can survive in soil for a long time, soil transmission is the main route, and it can also be transmitted through air and some tools.

1.5 Main insect pests. The main insect pests of edible fungi are fungus gnats and mites. Mites are not easily seen with the naked eye in the early stage, and mainly harm the mycelium, causing it to break and shrink. Mite pests can be introduced in both compost and casing soil, causing serious damage. Control method: the occurrence of mites is related to the substrate, casing soil, spawn, etc., so integrated control should be carried out.

2 Integrated control measures

2.1 Agricultural control

2.1.1 Select high-quality disease-resistant varieties. Select high-quality spawn suited to the time and place, with vigorous, non-aged, pure, and uncontaminated mycelium. Mother cultures should not be subcultured for more than 3 generations, and spawn for cultivation should be transferred from stock spawn.

2.1.2 Reasonable crop rotation. Different mushroom species, or different varieties of the same mushroom species, can produce metabolites with mutual antagonistic effects, which have a certain inhibitory and killing effect on pests, diseases, and contaminant microorganisms. Reasonable rotation can achieve a good preventive effect; mushroom growers with the conditions can replace the shed with a new one every year, for an even better contamination-prevention effect.

2.1.3 Stay away from sources of infection and do a good job of environmental sanitation. Before production each year, thoroughly clean the mushroom yard and eliminate places where pests breed. The cleaning scope includes the mushroom house and the courtyard. Last year's spent mushroom bags, straw pile garbage, compost, and all organic waste should be centrally burned or transported away, and weeds and peat soil should be removed. In the evening, use 15ml of 80% dichlorvos and 5ml of 1.8% abamectin, mixed with 40kg of water, for spraying. Apply once more after an interval of 1 week. Whitewash the mushroom house with bleaching powder plus lime slurry, and spread dry lime powder throughout the courtyard.

2.1.4 Reasonably regulate the relationship among temperature, humidity, and air. Temperature, humidity, and oxygen are important environmental factors affecting the quality and yield of various edible fungi, and the three must be managed as a whole. During fruiting, at suitable temperatures, such as 16-24°C for shaggy ink cap mushrooms and 14-16°C for button mushrooms, the number of fruiting bodies is greatest and the yield is highest; the suitable moisture content of the material is 60%-70%, and the relative air humidity should be controlled at 75%-80% during mycelial growth and 85%-90% during the fruiting body stage. Below 60%, the caps tend to curl upward, and above 95%, diseases are easily triggered. Edible fungi are all aerobic microorganisms, and fresh air is needed throughout their development, especially during fruiting body formation, when ventilation and air exchange must be done frequently. Mushroom houses with poor ventilation, excessive humidity, and excessively high temperature are prone to breeding contaminant microorganisms and pests.

2.1.5 Physical control. For armyworms, sticky traps coated with 40% polypropylene adhesive can be applied at strong lights, or a sugar-vinegar medicinal liquid can be used to trap and kill edible fungus mites; fungus gnats can be caught manually; mushroom bags with gall midges can be exposed to sunlight for 1-2h or sprinkled with lime powder. The water immersion method can also be used to control pests. For bottle cultivation and bag cultivation, water can be injected into the bottles or bags; for block cultivation, the cultivation blocks can be immersed in water and pressed down with a heavy object, soaked for 2-3h, and after soaking the bottles or bags should be drained and placed back in their original positions; mosquito and moth pests can be trapped and killed with black light lamps or energy-saving lamps.

2.2 Chemical control

2.2.1 Control of Aspergillus. Timely removal of waste material is the key to controlling Aspergillus (Figure 3). When filling spawn bottles, the material must not be too full, and the material must not come into contact with the cotton plug. After filling the bottles, wash the bottle mouth, remove organic matter, and keep the cotton plug clean. Applying 5mg/kg carbendazim can inhibit the growth of Aspergillus niger and Aspergillus flavus, but it must be applied after mushroom harvesting is completed.

2.2.2 Control of Trichoderma. There is still no ideal curative chemical for Trichoderma (Figure 4), which is called the cancer of edible fungi. Commonly used fungicides (carbendazim, prochloraz, thiophanate-methyl, etc.) can only inhibit Trichoderma rather than fundamentally kill it, and increasing the dose will simultaneously kill both Trichoderma and oyster mushroom mycelium. Therefore, creating growth conditions suitable for mycelial growth but unfavorable for Trichoderma reproduction is the fundamental measure to control the damage. Once Trichoderma damage occurs, ventilation and cooling should be carried out immediately, and plant ash should be used to cover the moldy areas to prevent mold spores from dispersing, so as to inhibit the expansion of the pathogen. For substrate in the mycelial growth stage after infection, the method of locally smearing medicinal liquid can be used to inhibit Trichoderma expansion. Commonly used liquids include 5% carbolic acid, 2% formaldehyde, 50% carbendazim or 75% thiophanate-methyl diluted 200 times, and 10% lime water. In addition, sprinkling lime powder on the contaminated area also gives a very good control effect.

2.2.3 Control of green mold. Lower the temperature and humidity of the mushroom house, increase ventilation, cover the moldy areas with plant ash, and cut off the airborne spread of mold spores. Take 9 parts quicklime, 1 part carbendazim, and an appropriate amount of water, and pour and brush the moldy area. In raw material cultivation, adding 100g of prochloraz per 100kg of dry material can thoroughly control and eradicate mold growth. After sprinkling potassium permanganate granules on the moldy area, spray water around the outside of the mold. Soak the mold with 5% lime water, and after the mold disappears, drain off the lime water and add new material; the mold can also be soaked directly with water. Brush the moldy area with 95% alcohol or kerosene, ignite and burn it, then dig it out and fill it in. For the control of bacteria, the culture medium and petri dishes must be thoroughly sterilized, and the temperature, pressure, and time during sterilization must all meet the requirements; after the culture medium is prepared, place it in a 30°C incubator for 1d before use to ensure there is no bacterial infection, and if there is infection, it can be sterilized again. Mother cultures or stock spawn must be guaranteed free of bacterial contamination. Antibiotics can be added to the culture medium, generally at a suitable concentration of 100-200 units per milliliter.