The Latest Control Methods for Tomato Gray Mold
Gray mold is a relatively serious and common disease on tomatoes, and it is also an important disease of greenhouse-cultivated tomatoes. It occurs in all vegetable-growing areas. In addition to harming tomatoes, it can also harm more than 20 crops such as eggplant, pepper, cucumber and bottle gourd. In years with low temperatures and frequent continuous rainy weather, the damage is severe. Now let us take a look at the control methods for tomato gray mold!
Damage Symptoms
Tomato gray mold can harm stems, leaves, flowers and fruits, but it mainly harms the fruits, usually with more severe disease on green fruits. When the stem is infected, small water-soaked spots appear at first, then expand into oblong or irregular light brown lesions. When humidity is high, a gray mold layer forms on the surface of the lesions. In severe cases, the stems and leaves above the diseased area wither and die, leading to wilt disease. Leaf disease mostly starts from the leaf tip and spreads inward between the lateral veins in a “V” shape. It is initially water-soaked, and after unfolding it becomes yellow-brown with irregular edges and alternating light and dark concentric rings. The boundary between diseased and healthy tissue is obvious, and a small amount of grayish-white mold layer forms on the surface. When fruits are infected, the remaining stigma or petals are usually infected first, then the disease spreads to the fruit or fruit stalk, causing the fruit skin to become grayish-white and develop a thick gray mold layer, appearing water-rotted.
Disease Development Pattern
The pathogen of tomato gray mold is a weak parasitic fungus and can live saprophytically on organic matter. Under low-light conditions, when air humidity is above 90%, disease can occur at 4-31°C, but the optimum temperature for development is 20-23°C, with a maximum of 32°C and a minimum of 4°C. It has strict humidity requirements. Disease begins when relative air humidity reaches 90%, and if high humidity lasts for a long time, the disease is severe. Low light, suitable temperature (around 20°C) and high relative humidity (above 90%) favor disease development. If the host grows weakly, the disease is easily induced. The infection period of the pathogen on tomatoes is the flowering and fruit-setting stage, and the pathogen spores latent in the pathogen body for a long time. If the tomato has already become rotten, that is, the infectious spores of gray mold have already invaded the interior of the fruit from the style or petals, rotting is bound to occur, and applying medicine at this time is already too late.
Control Methods
1. Agricultural control: The most important measure for controlling tomato gray mold is to make every effort to improve ventilation, light transmission and humidity reduction in the greenhouse, but at the same time keep the temperature from being too low. Second, strengthen fertilizer and water management so that the plants grow vigorously and are prevented from early aging and wounds caused by various factors. Diseased plants and diseased fruits should be removed and destroyed in time. After harvest, thoroughly clean the greenhouse and turn and sun-dry the soil to reduce sources of the pathogen.
2. Chemical control: 50% procymidone wettable powder at 1500-2000 times dilution, or 40% sulfur-carbendazim suspension at 400 times dilution, or 50% iprodione wettable powder at 1000-1500 times dilution, or 70% thiophanate-methyl at 800-1000 times dilution, etc., sprayed once every 7-10 days for 3-4 consecutive sprays. Note that the pathogen easily develops resistance, so the same agent should not be used within one growing season; instead, the above agents should be used in rotation.