How to prevent and cure white star disease?

Tea white spot disease occurs in all tea-producing provinces in China, mainly in high mountain areas, mainly harming tender leaves and new shoots, especially bud leaves and new leaves. After the leaves are damaged, they show light brown moist spots at the initial stage, and then gradually expand into small round gray spots. The disease spots often heal into irregular spots, which have a particularly serious impact on yield and quality. Let's take a look at how to prevent and control tea white star disease.

Symptoms of tea white star disease

Young leaves infected with the initial needle size brown spots, and then gradually expanded into a diameter of 2mm diameter of gray-white round spots, sunken in the middle, the edge with dark brown to purple-brown protuberant lines. When the humidity is high, the diseased part is scattered with black spots, and the number of diseased leaves is up to dozens to hundreds, some of which merge into irregular spots, resulting in leaf deformation or curl. The leaf veins are diseased and the leaves are twisted or deformed. The diseased spot of the tender stem was dark brown and then turned gray-white, and the diseased part also produced black grain spots, the length of the diseased tip was obviously shortened, the weight of 100 buds decreased, and the number of leaves increased. Serious spread to the whole shoot, forming a shoot withered.

The pathogen of tea white spot disease

The pathogen of tea white spot disease is tea leaf spot mold, which belongs to a subphylum fungus, the conidium is spherical to oblate, the size is 32 ~ 80 × 32 ~ 80 (micron), dark brown, with a papillary orifice at the top, initially buried, and then break through the epidermis exposure. Conidia oval to ovate, single cell colorless, size 3 ~ 5 × 2 ~ 3 (micron). After cultured on PDA medium for 48 hours, the pathogen grew white hyphae, then turned black, and produced many small black spots, that is, the fruiting body of the pathogen. The temperature limit of mycelial growth was 2-25 ℃, and the optimum temperature was 18-25 ℃. The growth stopped when the temperature was higher than 28 ℃. Light is beneficial to the growth and reproduction of bacteria.

The spread of tea white spot disease

The pathogen overwintered in diseased leaves or stems with mycelium and conidia. In the early stage of tea plant in the next spring, a large number of conidia were released from the conidia, which were transmitted by wind and rain and infected young stems and leaves when the humidity was suitable. After incubation for 1-3 days, new disease spots began to form, and conidia were produced on the disease spots. Repeated infection, so that the disease continues to spread. The disease is a low-temperature and high-humidity disease with a temperature of 16-24 ℃ and a relative humidity of more than 80%. The temperature higher than 25 ℃ is disadvantageous to the disease. The disease occurs mainly in spring and autumn every year, and the peak is in May. The disease is easy to occur in alpine tea garden or barren tea garden with lack of fertilizer and partial application of nitrogen fertilizer, and the disease is serious in overpicking and weakening of tea trees.

Prevention and control of tea white spot disease

1. Picking tea in batches and picking tea in time can reduce the infection of the disease and reduce the incidence of the disease.

2. The compost made by enzyme bacteria retting is advocated and compound fertilizer is applied to enhance the tree potential and improve the disease resistance.

3. From the end of March to the first ten days of April, 75% chlorothalonil wettable powder or 36% thiophanate methyl suspension, 50% carbendazim wettable powder, 1500 mancozeb wettable powder and 25% carbendazim wettable powder were sprayed at the end of March to early April.