Tomato bacterial spot

Tomato bacterial spot disease should have occurred, so how to better prevent and control it?

Occurrence pattern of bacterial spot disease in tomato

The pathogen mainly overwinters in diseased seeds, which is the main way of spreading to new vegetable areas. If infected seeds are sown, the seedlings can be infected. In addition, the pathogen can also overwinter in the field with the residual tissue of the diseased plants. The pathogen can survive for a long time in the dry residual tissue and become the source of infection in the early next year. After the disease occurs in the field, the pathogenic bacteria invade the plant through the natural stomata or wounds of the plant under the condition of water droplets or water film on the surface of the plant, multiply and spread in the intercellular spaces of the host's parenchyma tissue, destroy the host cells and enter the cells, and repeat the infection in the field many times, aggravating the damage.

The pathogen prefers a warm and humid environment, and the temperature range suitable for disease is 18-28℃; the most suitable environment for disease is 20-25℃, and the relative humidity is above 90%; the most suitable growth period for disease is from the end of seedling raising to around planting and fruit setting. The latent period for disease is 7-15 days. The disease is basically not caused below 15℃ and above 30℃, and the most suitable temperature for the growth and development of the pathogen is 27-30℃.

Tomato bacterial spot is a new disease that has emerged after the development of protected production in recent years. At present, there are only sporadic cases in Shanghai (mostly in old vegetable areas in the suburbs of neighboring cities), and the main peak period of the disease is from March to May in spring. The years of disease occurrence are mostly caused by high temperatures and heavy rains in early spring, the low-lying terrain of the protected area, poor drainage, the use of river sewage for watering, and the long closing time of the greenhouse. The cultivation conditions suitable for the disease are a temperature of 20-25℃; the presence of water droplets or wetness on the surface of the plant is an important condition for the disease. In addition, the fruits on the sunny side are susceptible to the disease, especially the fruits injured by sunburn are susceptible to the disease; the plants on the edge of the greenhouse are susceptible to strong wind and rain, causing wounds and severe disease. Extensive management, frequent watering, poor drainage, water accumulation after rain, insufficient fertilizer or partial nitrogen fertilizer application will aggravate the occurrence of the disease.

Tomato bacterial spot control measures

(1) Seed selection: Collect seeds from disease-free seed plants and select disease-free seeds.

(2) Seed treatment: The imported commercial seeds must be treated before sowing. The seeds can be soaked in 55℃ warm water for 10 minutes and then moved into cold water to cool. After being removed and dried, they can be germinated and sown.

(3) Crop rotation: It is recommended that severely diseased fields be rotated with other crops for 2-3 years to reduce the source of pathogens in the field.

(4) Strengthen field management: dig drainage ditches to lower the groundwater level, plant plants at a reasonable density, open the greenhouse in time to ventilate and reduce humidity, apply more phosphorus and potassium fertilizers to improve plant disease resistance, and use clean water for watering.

(5) Clean the fields: Prune and thin branches in time at the early stage of the disease, remove diseased and old leaves, clean the fields after harvest, remove diseased and damaged parts, and take them out of the fields for deep burial or burning. Deeply plow the soil, irrigate the protected areas and keep the greenhouses sealed. High temperature and high humidity can promote the decomposition and decay of residual tissues, reduce the survival rate of pathogens, and reduce the sources of reinfection.

(6) Chemical control: Start spraying at the early stage of the disease, spray once every 7 to 10 days, and continue for 2 to 3 times. The pesticides can be selected from 47% Carranon wettable powder 600-800 times diluted (125-165 grams per 666.6 square meters), 72.2% Prolec water-soluble liquid 700 times diluted (130 grams per 666.6 square meters), Fenghuamine wettable powder 800 times diluted (125 grams per 666.6 square meters), 30% DT wettable powder 600 times diluted (165 grams per 666.6 square meters), 77% Keshade wettable powder 700 times diluted (130 grams per 666.6 square meters), etc.