Analysis of the Causes of Meteorological Diseases in Oyster Mushroom Cultivation and Prevention Countermeasures

Years of oyster mushroom cultivation practice has proven that abnormal weather changes in spring, with temperatures suddenly rising or dropping sharply, can cause the same meteorological diseases in oyster mushrooms within the same climatic zone. If poorly managed, oyster mushroom fruiting bodies will wilt and die in large numbers within 1-7d, resulting in heavy losses. Therefore, studying meteorological diseases of edible fungi, utilizing weather forecast results, and formulating effective preventive measures have very important practical significance for reducing losses of edible fungi and improving the economic benefits of mushroom cultivation.

1 Typical Cases and Analysis

1.1 Typical Cases Case 1: In late April 1992, the author had just arrived at the Dongjiang Edible Fungus Factory in Wudu County to serve as a technical advisor. From April 21 to 25, rainy and overcast weather alternated continuously. The ambient daily minimum temperature was 5.5°C, the daily maximum temperature was 19.0°C, and the daily average temperature was 12.8°C. Inside the mushroom shed, the daily maximum temperature was 22.3°C, the daily minimum temperature was 11.5°C, and the daily average temperature was 16.7°C, which was 4-6°C higher than outside the shed. The relative humidity inside the shed was 80%-90%, suitable for fruiting. The mushroom logs and mushroom walls produced a large number of young buds, and their growth and development were normal. From April 26 to 30, suddenly affected by an exceptionally warm air mass and intense heat with clear skies, the ambient temperature suddenly rose to a daily maximum of 32.5°C, a daily minimum of 14.8°C, and a daily average of 23.6°C, causing the daily maximum temperature inside the shed to reach 37.6°C, the daily minimum to be 19.7°C, and the daily average to be 26.8°C. From April 29 to 30, large numbers of mushrooms inside the shed wilted and died. Upon inspection, no pesticides had been sprayed inside the shed recently, and all management was normal. A market survey revealed that other mushroom farmers with large sheds also experienced similar situations. Case 2: From March 13 to 17, 1998, the weather remained continuously clear, and temperatures rose quickly. The author was growing oyster mushrooms in the meteorological bureau courtyard. At that time, the ambient daily maximum temperature was 20.4°C, the daily minimum temperature was 5.8°C, and the daily average temperature was 13.2°C. Inside the shed, the daily maximum temperature was 26.5°C, the daily minimum temperature was 11.6°C, and the daily average temperature was 18.4°C. The oyster mushroom fruiting bodies were growing normally. From March 18 to 20, affected by an exceptionally cold air mass from the north, a rare cold wave with sharp temperature drop occurred. In one day, the ambient temperature dropped by about 15°C, with a daily maximum temperature of 5.0°C, a daily minimum temperature of -3.4°C, and a daily average temperature of -0.8°C. Inside the shed, the daily maximum temperature was 10.0°C, the daily minimum temperature was 0.0°C, and the daily average temperature was 4.9°C. The day before, willows were budding and spring was in full swing; overnight it turned into a world of ice and snow in winter. Within 3-7d, within the same climatic zone all around, especially the young buds and growing fruiting bodies of oyster mushrooms both outside and inside sheds, wilted and died over a large area. Upon investigation, both groups of affected oyster mushrooms mentioned above were medium-low temperature varieties.

1.2 Cause Analysis The optimal fruiting temperature for generally medium-low temperature oyster mushrooms is 10-15°C, while the optimal fruiting temperature for wide-temperature oyster mushrooms is 10-20°C. The optimal temperature for mycelial growth of most oyster mushrooms is generally around 25°C. Case 1 reflects that under normal climatic ambient temperatures, local oyster mushrooms in late April were at the optimal reproductive growth stage. Substrate nutrients were being transported from the mycelium to the fruiting bodies. After suddenly encountering a high-temperature period lasting about one pentad with a daily maximum temperature ≥32°C and a daily average temperature ≥23°C (with the daily maximum temperature inside the mushroom shed ≥35°C and the daily average temperature ≥25°C), if ventilation and cooling measures were not taken in time, the substrate nutrient transport would become disordered, reversing from the fruiting bodies back to the mycelium, entering vegetative growth. This caused the fruiting bodies to stop receiving nutrients or have nutrients flow back to the mycelium, rapidly wilting and dying. However, after entering May, as the ambient daily average temperature steadily rose to ≥20.0°C, the medium-low temperature oyster mushrooms gradually entered the temperature range suitable for mycelial growth but not suitable for fruiting body growth. Therefore, fruiting gradually stopped and entered the summer mycelium-culturing stage. Under conditions similar to the above sudden temperature rise, the above phenomenon would not occur. Case 2 reflects that local oyster mushrooms in mid-March, under normal climatic ambient temperatures, were at the lower limit of the optimal temperature for reproductive growth and fruiting. Substrate nutrients slowly flowed to the fruiting bodies, and the fruiting bodies grew slowly. After suddenly encountering a low-temperature attack lasting about one pentad with a daily minimum temperature ≤0°C and a daily average temperature around 0°C, if warming and insulation measures were not taken in time, the substrate nutrients would slowly or completely stop being transported to the fruiting bodies, causing the fruiting bodies to gradually wilt and die. However, in the cold winter when the average temperature remains ≤0°C, it is very difficult to form fruiting body young buds. Therefore, even if the daily temperature drop is large, the above phenomenon cannot occur.

1.3 Analysis of Fruiting Body Death Characteristics From the comparative analysis of Case 1 and Case 2, the fruiting bodies in Case 1 died very quickly, generally in 1-3d they could die in large numbers, or even be completely wiped out. The fruiting bodies in Case 2 died more slowly, generally in 3-7d. In Case 1, the dead mushroom bodies quickly wilted and rotted, while in Case 2, the mushroom bodies slowly turned yellow, shrank, and died.

2 Spatiotemporal Distribution Characteristics of Disastrous Weather

From the analysis of temperature data from March to May during 1970-2004 in the nine counties of Longnan, under normal temperature conditions, the frequency of sudden temperature surges during this period producing weather similar to Case 1 was about 30%, that is, once every three years on average. During this period, the frequency of sudden cold waves and strong temperature drops producing weather similar to Case 2 was 40%-50%, that is, once every two years on average. However, once these two types of weather occur, their range is wide. Especially since 1986, the climate has been warmer, and early spring temperatures rise quickly. Under normal climatic ambient temperatures, once a cold wave or strong temperature drop lasting about one pentad with an ambient daily minimum temperature ≤0°C and a daily average temperature around 0°C occurs suddenly, Case 2 oyster mushroom freezing damage will appear. Similarly, under normal climatic ambient temperatures, once a high-temperature period lasting about one pentad with an ambient daily maximum temperature ≥32°C and a daily average temperature ≥23°C (with the daily maximum temperature inside the mushroom shed ≥35°C and the daily average temperature ≥25°C) occurs suddenly, Case 1 oyster mushroom heat damage will appear. Both of the above situations occur in spring from March to May in Longnan City, that is, during the transition between cold and warm seasons. Similar phenomena rarely occur in other seasons.

3 Prevention Countermeasures

In the springs of 1999-2004, Case 2 weather occurred 3 times and Case 1 weather occurred 2 times. Based on years of oyster mushroom cultivation experience, through research and analysis of oyster mushroom cultivation site selection, mushroom shed construction methods, and management methods, we formulated relatively scientific defensive measures. Through nearly 5 years of experiments and comparison with conventional methods, the disaster reduction effect was remarkable, with basically no occurrence of Case 1 or Case 2 phenomena. However, in the survey, it was found that with conventional management methods, 50%-60% of mushroom sheds experienced Case 1 and Case 2 disasters, with relatively large losses. The defensive measures are summarized as follows:

3.1 Actively listening to weather forecasts and taking effective measures to prevent problems before they occur is one of the effective methods for preventing meteorological diseases in oyster mushrooms. In spring, arrange oyster mushroom production according to the short- and medium-term weather forecasts issued by local meteorological departments. If the forecast indicates that temperatures will continue to rise in the near future and high-temperature periods will occur, attention should be paid to promptly opening the ventilation windows of each mushroom shed, increasing ventilation and heat dissipation, and using straw curtains to block direct sunlight. In addition, when building mushroom sheds, a site with good ventilation conditions should be reasonably selected.

3.2 There are many abandoned mountain caves in the Longnan mountainous area. Actively utilizing some abandoned artificial caves or natural caves in the Longnan mountainous area to cultivate oyster mushrooms is also a feasible way to prevent meteorological disasters in oyster mushroom cultivation. Surveys found that oyster mushrooms grown in mountain caves rarely showed Case 1 or Case 2 phenomena. Because the annual temperature variation in mountain caves is warm in winter and cool in summer, sharp hot and cold changes outside the cave have little effect on the temperature inside the cave. As long as attention is usually paid to improving lighting and ventilation conditions inside the cave, oyster mushrooms can be safely produced in all four seasons inside the cave.

3.3 Research shows that using semi-sunken greenhouse sheds to cultivate oyster mushrooms, affected by ground temperature, results in relatively small temperature changes inside the shed. Before low-temperature cold air arrives, promptly cover the greenhouse shed with straw curtains for insulation to minimize the temperature drop, allowing oyster mushroom young buds to grow normally. After the snow stops and the sky clears, the curtains can be appropriately lifted during the day to increase temperature and ventilation, and covered at night for insulation. After the ambient temperature returns to normal, normal management can resume. After high-temperature periods arrive, promptly opening the ventilation windows of the mushroom shed and blocking direct sunlight to minimize the range and speed of temperature rise is also one of the effective ways to prevent meteorological diseases in oyster mushrooms.

3.4 In addition to the above prevention methods, selecting excellent varieties and scientifically arranging variety temperature types according to the season is also a feasible path.