Answers to Key Questions on Tea Tree Mushroom Cultivation Techniques

Tea tree mushroom, also known as the tea tree mushroom (Agrocybe aegerita), is a rare mushroom variety newly developed in recent years and well received in domestic and international markets, becoming a highlight among varieties promoted for cultivation in various regions. Gutian County, Fujian Province alone reaches an annual cultivation volume of 100 million bags. Because the cultivation history of the tea tree mushroom is short, production management lacks standardization, and both the mycelium and fruiting bodies of this mushroom contain an almond-like fragrance, pests and diseases are relatively numerous, resulting in substandard yields, declining quality, and excessive pesticide residues in products, directly affecting economic benefits and the sustainable development of the industry. With the implementation of the national "Law on the Quality and Safety of Agricultural Products" and the requirements of market access systems, future requirements for pollution-free products will be even stricter. Here, a comprehensive analysis is provided on the key issues and difficulties in tea tree mushroom cultivation techniques, along with proposed solutions, for mushroom farmers to reference in production practice.

1 Misconceptions in Substrate Formulation Lead to Substandard Yields

1.1 High-Yield Standard

When the biological characteristics and physiological-ecological conditions of the tea tree mushroom meet requirements, its biological conversion rate can reach 133%, that is, 100 kg of substrate (dry material) can produce 133 kg of fresh mushrooms. According to the current situation in the Gutian mushroom-growing area, cultivation bags of 15 x 30 cm are commonly used, with each bag containing 300 g of dry material; a yield of 400 g of fresh mushrooms per bag meets the high-yield standard. If following the specifications and quality requirements for fresh-keeping mushrooms, it should also be no less than 300 g. However, many current cultivation households fail to meet the standard.

1.2 Factors for Not Meeting the Standard

Although there are many factors for substandard yields, one very important reason is improper substrate preparation. The misconceptions are: first, one-sided emphasis on reducing costs by decreasing the amount of wheat bran, with some wheat bran proportions accounting for only 10%, and some even only 5%; second, the amount of lime used is the same in spring, summer, autumn, and winter; third, the time from mixing the substrate and filling bags to placing them in the sterilizer is prolonged, causing the substrate to sour and spoilage and destruction of nutrients.

1.3 Basic Requirements

The entire production cycle of vegetative growth and reproductive growth of the tea tree mushroom requires 10 months and consumes large amounts of nutrients. If nutrient supply cannot keep up and there is a congenital deficiency, high yields cannot be achieved.

1.3.1 Wheat Bran The main nutrient for tea tree mushroom cultivation is protein in organic matter. The existing cultivation raw material cottonseed hulls have a protein content of only 4%, while wheat bran has a protein content of 13.5%, more than 3 times that of cottonseed hulls; especially, the amino acid content in wheat bran protein is as high as 46%, making it the main nitrogen source for tea tree mushroom nutrition and also an additive of VB1; therefore, wheat bran is an indispensable nutrient in the formula. Its reasonable formula requires wheat bran to account for no less than 15% of the total substrate.

1.3.2 Lime As a pH buffer for the substrate and also to increase calcium nutrients, the general dosage is 2%-3%. The specific dosage should be increased or decreased according to the daily air temperature when mixing ingredients; use less when the temperature is below 20°C and more when the temperature is above 28°C, with the aim of controlling substrate spoilage.

2 Contamination by Weed Molds and Its Control

2.1 Causes of Contamination

The contamination rate of tea tree mushroom bags by weed molds is higher than that of other mushrooms. The main reason is the relatively large cultivation volume; generally, a cultivation household makes at least 5,000 bags at a time, and up to 10,000 bags, resulting in a heavy workload and loss of technical control in links such as substrate mixing, bag filling, sterilization, inoculation, and mycelial culture. Especially in old mushroom-growing areas, contaminated bags are not handled well, the index of weed mold spores in the space continuously increases, and the resistance of weed molds becomes stronger and stronger.

2.2 Common Weed Molds

Mainly competitive weed molds such as Trichoderma viride, Neurospora, Penicillium, and yellow-red Monascus. Especially Trichoderma viride is extremely harmful; once contaminated, the mushroom bags are rendered useless.

2.3 Control Measures "7 in Place"

2.3.1 Add water to cottonseed hulls 24 hours in advance, pile them up, and ferment.

2.3.2 After adding wheat bran, the time from mixing substrate and filling bags to placing them in the sterilizer should not exceed 6 hours to prevent the substrate from becoming sour.

2.3.3 The sterilization temperature standard is to maintain 100°C for 24 hours after reaching that temperature.

2.3.4 During handling, prevent holes from being made in the bags.

2.3.5 Inoculation time should be chosen at night on sunny days, with strict aseptic operation.

2.3.6 During mycelial culture, pay attention to temperature control, moisture prevention, ventilation, and light avoidance.

2.3.7 Turn and inspect the piles on schedule, and promptly handle any weed mold contamination found. When mite damage occurs, use 73% Propargite EC at 2000-3000 times dilution for spray control.

3 Control of Mushroom Gnats

3.1 Causes and Characteristics of Insect Damage

Because of the unique fragrance of tea tree mushroom mycelium, it attracts large numbers of mushroom gnats to invade and feed on the mycelium. The affected parts have shrunken mycelium, and the substrate turns black, becomes moldy, and emits a foul odor, affecting mushroom production. Mushroom gnats are a major enemy of tea tree mushroom cultivation.

3.2 Morphological Characteristics of Mushroom Gnats

There are many varieties of mushroom gnats. The mushroom gnat currently occurring on Gutian tea tree mushrooms belongs to the mushroom-feeding gall midge. The adult has a black head and thorax, transparent wings, and a mottled white abdomen. After the mushroom bag is opened, it enters the inner surface of the bag, destroys mycelial growth, and lays eggs. The eggs are milky white at first and later turn yellow; the egg stage lasts 4-5 days. Mature larvae resemble nematodes, 2-3 mm long; the smaller ones are as thick as a hair, and the larger ones are close to the thickness of a toothpick. Each adult can reproduce 8-12 small larvae, and the larvae pupate in 10-15 days. The pupa is 1.3-1.6 mm long, and the pupal stage lasts 6-7 days. The generation cycle of sexual reproduction is about 30 days.

3.3 Control Measures "Four Keys"

3.3.1 Purify the environment Do a good job of sanitation around the mushroom house, and spread lime for disinfection.

3.3.2 Physical control Install nylon gauze on the doors and windows of the mushroom house to prevent adults from flying in to lay eggs.

3.3.3 Chemical control Use gas-phase disinfectant for vaporized disinfection in the mushroom house, or spray once with 50% phoxim EC at 1000 times dilution;

3.3.4 Spray 3-4 days before opening the bags to prevent damage According to the pesticide requirements for pollution-free cultivation, sanitary balls can be crushed into powder and burned, or mosquito coils can be lit to drive them away; pesticides should be selected from broad-spectrum, low-toxicity, short-residue varieties, such as fipronil, acetamiprid, dimehypo, buprofezin, or 50% dichlorvos EC. Some mushroom farmers use aluminum phosphide, after which tea tree mushrooms emerge 15 days later and grow poorly; this is because aluminum phosphide absorbs air and water vapor and volatilizes to form toxic and sour gas, and the mycelium is harmed after contact, or even rots and becomes moldy, affecting mushroom production.

Pesticide application should "match the target." Any pest or disease has its symbiotic patterns; only by selecting the right pesticide and the best control period can the control effect be achieved. When mite damage occurs during the bag culture period, 73% Propargite EC can be selected and diluted 2000-3000 times for spraying. The use of any chemical pesticide is prohibited during the mushroom-growing period. After clearing the damaged mushroom bodies and their substrate layer, to prevent recurrence of insect damage, biological pesticides and environmentally friendly pesticides can be applied, for example avermectin (100 mL/bottle) + acetamiprid (275 mL/bottle) + diflubenzuron (350 mL/bottle). After mixing these 3 pesticides, dilute with 250 kg of water and spray; the insecticidal effect is very good and meets the pesticide requirements for pollution-free cultivation.

Highly toxic chemical pesticides prohibited by the state, such as methamidophos, carbofuran, and chlordimeform, must not be applied under any circumstances.

4 Two Newly Discovered Fungal Coat Diseases of Mushroom Logs and Their Control

4.1 Disease Characteristics

After 2-3 batches of tea tree mushrooms have been grown and harvested, a layer of fungal coat that is yellow or white, smooth on the surface, and sticky often appears on the surface of the mushroom log, later becoming dull; another type is a coffee-colored reticular covering appearing on the surface layer of the mushroom log. These 2 newly discovered fungal coat diseases can cause tea tree mushroom mycelium to turn black, soften, and become moldy and foul-smelling, no longer producing mushrooms, and becoming waste bags.

4.2 Pathogens

Of the above 2 diseases, the former belongs to branch mold fungal coat disease, with the pathogen being Cladobotryum varium; the latter has the pathogen Sepedonium brunneum.

4.3 Control Measures "Four Checks"

4.3.1 Humidity limit During watering, the spatial humidity should not exceed 90%.

4.3.2 Oxygen increase Pay attention to ventilation and air exchange.

4.3.3 Temperature control When the air temperature is high, add shade coverings and spray water on the shed roof to cool it down.

4.3.4 Isolation Move mushroom bags that have already developed the disease elsewhere to prevent the pathogen from spreading.

5 Infectious Diseases of Fruiting Bodies and Their Control

5.1 Disease Types

During the fruiting body growth stage, various infectious diseases such as brown rot, soft rot, damping-off, black spot, moldy rot, or empty sore disease often occur, causing reduced yield and income and declining quality of tea tree mushrooms.

5.2 Symptoms

The mushroom bodies affected by the above infectious diseases turn brown in color, shrink, become moldy and rot, and lose commercial value.

5.3 Control Measures "Five Key Points"

5.3.1 Do a good job of disinfecting the mushroom house and purifying the environment.

5.3.2 During the mushroom production period, the water used should be clean, ventilation and air exchange should be strengthened, and high temperatures during the mushroom-growing period should be avoided.

5.3.3 Remove and burn damaged mushrooms promptly, then stop watering, increase ventilation, and reduce spatial humidity.

5.3.4 After harvesting, spray the mushroom bags with streptomycin at a 1:50 dilution to kill pathogens latent in the bags and avoid recurrence during the second flush of mushroom growth.

5.3.5 Harvest mature mushrooms early and process them.