How to prevent and control gray mold in lettuce? A detailed explanation of the latest prevention and control methods
Gray mold is the main disease of lettuce under protected cultivation. After it occurs, it often reduces yield by about 30%, especially for overwintering lettuce that develops the disease in spring, which can reduce yield by more than 50%. So how should lettuce gray mold be prevented and controlled? Let's take a look together.
1. Disease symptoms
When seedlings develop the disease, the seedlings become water-soaked and rotted, with a gray mold layer on the surface. After transplanting, the disease mostly starts from leaves closer to the ground. The leaves first show water-soaked lesions, and under high temperature and high humidity conditions the diseased part rapidly expands and turns brown, while the base of the diseased leaves also turns reddish brown. Finally, the stem base of the diseased plant rots and dies, causing the stems and leaves above ground to wither and die.
2. Conditions for disease occurrence
Gray mold is a fungal disease. The pathogen overwinters as mycelium, sclerotia, and conidia in diseased plant residues and soil, and the following year spreads through agricultural operations and watering, invading through wounds and lenticels of young tender tissues to cause disease. Disease can occur between 5-31°C, but it is most severe when air humidity is above 90% and the temperature is between 20-25°C. The occurrence of gray mold is closely related to the growth status of the vegetables and the external environment. When plants grow poorly, or during the transition between winter and spring, because too much watering in the greenhouse creates high temperature and high humidity conditions, the disease is extremely likely to occur and becomes severe.
3. Prevention and control measures
1. Agricultural control
Before sowing, the seedbed and seeds must be strictly disinfected. When transplanting, choose strong seedlings and remove diseased and weak seedlings. Keep the plant and row spacing at 20×20 cm. Too sparse is not conducive to yield, while too dense will cause the plants to grow excessively, with thin and weak stems, affecting yield and making them prone to disease. Proper crop rotation in production can not only ensure strong crop growth, but also improve disease resistance and reduce disease damage. During winter cultivation, attention should be paid to ventilation and moisture removal. After each watering, close the greenhouse to raise the temperature, then ventilate to exchange air, effectively reducing the relative air humidity inside the greenhouse. Fertilization should be based mainly on organic fertilizer, with reasonable additional application of phosphorus and potassium fertilizer, and avoid over-application of nitrogen fertilizer, so as not to make the vegetables too tender.
2. Chemical control
When the disease occurs, spray thiophanate-methyl, carbendazim, or chlorothalonil, applying once every 7-10 days for 2-3 consecutive times. Alternating several pesticides gives better results.
The above is an introduction to the prevention and control methods for lettuce gray mold. We hope it can help you. If you want to learn more related knowledge, please stay tuned to us.