Identification of Mushroom Rust Spot Disease Symptoms and Introduction to Control Methods
The mushroom (scientific name: Agaricus campestris) is composed of two parts: the mycelium and the fruiting body. The mycelium is the vegetative organ, and the fruiting body is the reproductive organ. Mushrooms have as many as 36,000 sexes, and mature spores germinate into hyphae. The hyphae are multicellular, have septa, and elongate by apical growth; they are white, slender, cottony, and gradually become filamentous. The hyphae interweave with one another to form a dense mass known as the mycelium. After the mycelium has saprophytically colonized the substrate, the dark brown compost turns light brown. When mature, the fruiting body of the mushroom closely resembles an open small umbrella. It is composed of parts such as the cap, stipe, gills, annulus, and pseudorhiza. Most mushrooms can be used as food and medicine, but poisonous mushrooms can harm people.
The mushroom belongs to the class Basidiomycetes, order Agaricales, family Agaricaceae, genus Agaricus, and is the edible fungus that is most widely cultivated, highest in yield, and largest in consumption in the world. Mushrooms prefer cool, damp environments, such as deep in the woods or artificially created cool, damp environments. The temperature range for mushroom mycelium growth is 4-32°C, with 20-25°C being the most suitable. At 20-25°C, the mycelium grows relatively quickly, is dense, and is robust and vigorous. Above 25°C, although the mycelium grows quickly, it is sparse and weak; if it reaches above 30°C, the mycelium is damaged and its vitality decreases; below 15°C, the mycelium grows slowly. In winter it can endure a low temperature of 0°C. The temperature range for fruiting body growth is 5-25°C, with the optimum temperature between 14-16°C. At 14-16°C, the fruiting body grows relatively quickly, the stipe is short and sturdy, the flesh is thick, and the quality is good with high yield. Above 18°C, although the fruiting body grows quickly, the stipe is slender, the skin is thin, and the cap opens easily, resulting in poor quality; below 12°C, the fruiting body grows slowly.
After pinning, if there is a spell of high temperature above 23°C for several consecutive days, it will cause mushroom death and reduce mycelium vitality. At a room temperature below 5°C, the fruiting body stops growing, and mycelium growth is also extremely slow. The suitable temperature for mushroom fruiting bodies to release spores is 18-22°C. When the temperature exceeds 25°C, spores will not be released even if other conditions are suitable. Generally, after about 2 days of culture, the spores will fall, and isolation can be carried out once the spores in the culture dish have turned dark coffee-colored. The suitable temperature for spore germination is 23-25°C; if the temperature is too high or too low, it will prolong the germination time or even prevent germination. The mushroom is a saprophytic fungus and cannot use solar energy for photosynthesis; it relies entirely on the nutrients in the compost for growth and development. Among the nutrients, carbon-containing substances are the most important, followed by nitrogen-containing substances and inorganic salts.
Introduction to and Control of Mushroom Rust Spot Disease
What is mushroom rust spot disease?
Mushroom rust spot disease is also called brown spot disease or bacterial blotch disease. Its pathogen is an acidophilic Pseudomonas species, Pseudomonas tolaasii. It is spread through media such as insects, tools, and the hands of workers. The disease is severe when the pH of the casing soil on the mushroom bed is below 5.5, ventilation is poor, humidity is too high, and the cap remains constantly wet and sticky after watering.
Symptoms of mushroom rust spot disease:
It generally infects only the epidermal layer of the mushroom cap, causing yellow-brown rust-like spots of varying sizes to appear at first, which later gradually turn brown or black; sometimes slime-covered scars also appear on the cap. This disease spreads rapidly. When the infection is mild, the mushroom shape remains normal; when severe, as many as several hundred sunken spots appear on the cap, or the lesions enlarge and become stripe-like, and the fruiting body becomes deformed. The stipe is sometimes infected and also develops longitudinal sunken spots.
Control methods for mushroom rust spot disease:
1) When casing, adjust the pH of the soil layer to 6.5-8, and strengthen ventilation during cultivation.
2) When the disease is severe, control the temperature and humidity of the mushroom house. Also spray the mushroom bed with 0.04% oxytetracycline and 0.04% streptomycin once each every other day. Subsequent watering of the mushroom bed should adjust the pH to 8 until the pH of the soil layer is maintained at 6.5-7.5.
3) Sprinkling a thin layer of quicklime powder on the surface of the casing soil layer can also effectively control the development of the disease.