Tomato Gray Spot Materials and Practice

What should we do if gray spot disease occurs when we grow tomatoes? Here are some precautions for gray spot disease of tomatoes:

Tomato gray spot pathogen

Ascochyta lycopersici

Tomato gray spot symptoms

It occurs in all places, mainly harming leaves. When the leaves are infected, small brown spots appear at first, which quickly expand into nearly circular and oval spots. The spots are gray-brown, with a diameter of 10 to 20 mm or even larger, and the ring pattern is not obvious. There are small black spots on the spots, which are arranged in a ring pattern. The spots are easy to rupture in the later stage, and in severe cases, the diseased leaves wither early. The law of disease occurrence The pathogen overwinters in the soil or on the surface with the diseased remains in the conidia. The conidia release conidia in the following year to infect tomatoes and cause the disease. New conidia are produced in the diseased part, which are spread by wind and rain for re-infection, and the disease continues to expand and spread. The pathogen likes a warm and humid environment. It is easy to get sick above 20°C, but the determining factor of whether the disease occurs or not is humidity. A high humidity environment, especially rain, plays an important role in the release and spread of conidia.

Tomato gray spot control method

① Agricultural measures: Use high ridges covered with mulch film and the density should be appropriate. Severely diseased land should be rotated with non-Solanaceae vegetables for more than 2 years. Apply fertilizers reasonably and avoid partial or excessive nitrogen fertilizers. Properly control the amount of watering and drain the water in the field in time after rain. When cultivating in protected land, pay attention to ventilation and moisture removal to reduce the humidity in the greenhouse. Do a good job of field cleaning and remove diseased leaves or clean up diseased residues in time.

② Chemical control: Carry out chemical control in time at the early stage of the disease. You can use 500 times of 75% thiophanate-methyl wettable powder, 300 times of 50% carbendazim wettable powder, 800 times of 70% thiophanate-methyl wettable powder, 600 times of 30% copper hydroxide, or 1:1:200 Bordeaux mixture for spraying. Spray once every 7 days, and control 2 to 3 times continuously.