What are the control methods for several tea plant diseases?

I. Tea gray blight

Tea gray blight is a common and serious leaf disease of tea plants. The disease is widely distributed throughout tea-growing areas. Affected plants often grow poorly, with weak new growth, thin and weak buds, and premature aging, seriously affecting yield.

Control methods for this disease:

1. Strengthen management and cultivate healthy tea plants. Use pesticides rationally to avoid phytotoxicity; carry out timely intertillage and weeding to loosen the soil; do a good job of tea garden drainage or drought and cold resistance work, create an environment favorable to tea plant growth, promote tea plant vigor, and improve disease resistance.

2. Clean up the garden and reduce sources of the pathogen. For heavily diseased tea gardens, diseased leaves should be removed during winter and spring, dead branches and fallen leaves should be cleared away, or winter plowing of the tea garden should be carried out to deeply bury diseased surface leaves, thereby blocking the source of the disease. During the disease period, remove diseased leaves to prevent infection and spread.

3. Spray pesticides promptly to control the spread of the disease. Because the occurrence of this disease has a certain relationship with tea green leafhoppers, mites, black rot, and red rust, control of this disease should be combined with control of the above pests and diseases. The following agents can be sprayed: 0.6% half-strength lime Bordeaux mixture (picking only 20 days after spraying), 70% thiophanate-methyl wettable powder 1000-1500 times dilution, agricultural antibiotic actidione 30-50 ppm (picking 5 days after spraying), antibiotic fungomycin 1 ppm (picking 7 days after spraying), 80% zineb wettable powder 600-800 times dilution (picking 15 days after spraying). The spray volume is 60-75 kg per mu, sprayed once every 10-15 days, for a total of two sprays. In tea gardens or nurseries that are not being picked, the above agents can also be sprayed. According to actual conditions, the interval can also be appropriately shortened and the number of sprays increased to achieve better disease control.

For tea green leafhoppers and mites, the following agents can be sprayed according to pest conditions: 40% dimethoate emulsion 500-1000 times dilution, 90% trichlorfon crystal 500 times dilution, 80% dichlorvos emulsion 500 times dilution. These insecticides cannot be mixed with the alkaline pesticide Bordeaux mixture, otherwise efficacy will be reduced and phytotoxicity may result.

II. Tea blister blight

Tea blister blight is a fungal disease, relatively common in distribution, and an important disease in high-mountain tea areas. This disease mainly infects the young tender shoots of tea plants. It not only greatly affects yield, but the dry tea made from damaged leaves tastes bitter, is brittle, and has many fragments, significantly reducing quality. Control methods for this disease:

1. Strengthen seedling quarantine. In diseased areas, all diseased tea seedlings, scions, and cuttings should be prohibited from being transported out, in order to protect disease-free areas and new tea gardens.

2. Strengthen tea garden management. Weed frequently; adjust the types of fertilizer and the timing of application, appropriately increase phosphorus and potassium fertilizer, and avoid partial or excessive application of nitrogen fertilizer; prune promptly and remove diseased branches and leaves.

3. Harvest tea reasonably. After late September, if there is more cloudy weather and low temperatures, timely batch picking should be carried out, picking 1 bud with 2-3 leaves while retaining fish leaves, and the opposite-leaf buds (dormant buds) should be picked clean in time.

4. Eliminate places where the pathogen overwinters in summer. In extremely hot weather, the pathogen cannot survive the summer in tea gardens with long sunshine and high temperatures, and can only continuously infect and overwinter on shaded tea plants. Therefore, strengthening tea garden management to make the tea garden well ventilated and well lit, thereby eliminating places where the pathogen overwinters in summer, is an important measure to prevent the occurrence of this disease.

5. Chemical control. Available agents include: systemic organic fungicides such as carbendazim, thiophanate, and thiophanate-methyl. Spray 500-1000 times dilution of the above agents per mu, with a spray volume of 75-100 kg per mu, once every 10 days, for a total of 2-3 sprays (picking 15 days after spraying). If the above agents are unavailable, 0.6% half-strength lime Bordeaux mixture can also be sprayed, 75-100 kg per mu, once every 10-14 days (picking 20 days after spraying).

III. Tea black rot

Tea black rot is also relatively common in some tea areas, with severe plant incidence reaching as high as 52%. If not well controlled, it not only reduces tea yield year after year, but tea plants gradually weaken and may even die. Control methods:

1. Combined with pruning, remove diseased branches and leaves to reduce the source of inoculum. For severely affected tea gardens, heavier pruning should be carried out, and the pruned diseased branches and leaves should be removed and burned. After pruning, spray 0.7% double-strength lime Bordeaux mixture once comprehensively, with 60-75 kg of spray liquid per mu.

2. Improve the surrounding environment of the tea garden and enhance ventilation in the tea garden. Remove overly dense shade trees and weeds such as forests and shrubs around the tea garden, so that the tea garden is well ventilated and well lit.

3. Strengthen inspection, detect early, and spray pesticides promptly for control. Frequently inspect whether leaves are diseased. Once discovered, remove diseased leaves and branches immediately and carry out spray blocking to prevent spread. Spray agents include: 0.7% equal-strength lime Bordeaux mixture, 75 kg per mu, sprayed once every two weeks (picking 20 days after spraying); 2% gangmycin 1000 times dilution, 60-100 kg per mu, or 5% tianan aqueous solution 600 times dilution, or 50% carbendazim wettable powder 800-1000 times dilution, or 70% thiophanate-methyl wettable powder 800-1000 times dilution, or 50% wenkuliling emulsion 800-1000 times dilution, 75-100 kg per mu.