Control methods of Botrytis cinerea in tomato

Botrytis cinerea is a serious and common disease on tomatoes, and it is also an important disease of tomatoes cultivated in greenhouses. It occurs in all vegetable areas. In addition to harming tomatoes, it can also harm more than 20 kinds of crops, such as eggplant, pepper, cucumber, bottle gourd and so on. The harm is serious in years with low temperature and continuous overcast and rainy weather. Let's take a look at the prevention and control methods of tomato gray mold.

Harmful symptoms

Botrytis cinerea can do harm to stems, leaves, flowers and fruits, but it mainly harms fruits. When the stem is infected, it begins to show a small flooded spot, and then expands into an oblong or irregular shape, light brown. When the humidity is high, there is a gray mildew layer on the surface of the disease spot, and in serious cases, the death of the stems and leaves above the pathogenic part leads to Fusarium wilt. The disease of the leaf mostly starts from the tip of the leaf, extends inward in the shape of "V" along the branch veins, appears as a water immersion at first, and becomes yellowish brown after expansion, with irregular edges, deep and shallow wheel lines, obvious boundary between disease and healthy tissue, and a small amount of gray-white mildew layer on the surface. When the fruit is infected, most of the residual stigmas or petals are infected at first, and then expand to the fruit or stalk, resulting in a gray-white pericarp with a thick gray mildew layer and water rot.

Morbidity regularity

The pathogen of tomato Botrytis cinerea is a weak parasite, which can saprophytic life on organic matter. Under low light conditions, the disease can occur at 4: 31 ℃ when the air humidity is more than 90%, but the suitable temperature for development is 20: 23 ℃, the highest is 32 ℃, the lowest is 4 ℃, the humidity is strict, and the disease begins when the air relative humidity reaches 90%. The high humidity lasts for a long time and the disease is serious. Low light, suitable temperature (about 20 ℃) and high relative humidity (more than 90%) are beneficial to the disease. If the growth of the host is weak, it is easy to induce the disease. The infection period of the pathogen to the tomato is the flowering and fruit-setting stage, and the pathogenic spores are latent in the pathogen for a long time, if the tomato has rotted, that is to say, the infected spores of Botrytis cinerea have invaded the fruit from the style or petals. It is bound to cause rot, and it is already too late to use the medicine again.

Prevention and cure method

1. Agricultural prevention and control: the most important measure to control tomato gray mold is to do a good job in ventilation, light transmission and humidity reduction in the greenhouse, but at the same time keep the temperature not too low. Secondly, it is necessary to strengthen fertilizer and water management to make plants grow strong and prosperous, and prevent premature senility and wounds caused by various factors. Diseased plants and diseased fruits should be cleared and destroyed in time, clear the garden thoroughly after harvest and turn over the soil, which can reduce the source of germs.

2. Chemical control: 50% Sukeling wettable powder 1500 times, or 40% polysulfide suspension 400 times, or 50% prohydantoin 1000 times, or 70% methyl topiramate 800 times 1000 times, sprayed every 7 days, 3 times 4 times in a row. It should be noted that bacteria are prone to drug resistance, so the same drug should not be used in a growing period, and the above-mentioned agents should be used in rotation.