Symptoms and Control techniques of Botrytis cinerea in lettuce

A reader in Jiangsu asked, what are the symptoms and control methods of lettuce gray mold? Answer: Botrytis cinerea of lettuce mainly harms leaves and stems and can be infected from seedling stage to adult stage. Get sick at the seedling stage. The leaves and young stems rotted in the form of water immersion, and the diseased part was covered with gray mildew layer. The leaves are infected. Starting from the mature leaves near the ground, the disease initially produces water-immersed spots, which are grayish brown irregular after enlargement. In case of continuous overcast and rainy fields with high humidity, the disease part expands rapidly and spreads to the internal leaves. When the humidity is high, a thick layer of gray mold is produced, that is, the conidiophores and conidia of the pathogen. The stem is infected. Water-immersed spots were produced at the base of the initial stem, which enlarged around the stem, and a thick gray mildew layer was produced when the field humidity was high, which caused the aboveground stems and leaves to wither and the diseased plants gradually withered and died. Control measures (1) crop rotation. Promote 2-3 year rotation with non-Compositae vegetables or Gramineae crops. (2) thick and thin ground preparation. Apply fully mature organic fertilizer, apply sufficient base fertilizer, cultivate in deep ditch and high border, and often clean up the gully system to prevent diseases caused by stagnant water after rain. (3) strengthen cultivation management. Suitable time for sowing, planting, reasonable close planting, greenhouse cultivation pay attention to ventilation, and pay attention to regulating the microclimate in the greenhouse, mainly ecological disease prevention, so as to make the plant grow strong and improve the ability of disease resistance. (4) to clean up the countryside. The disease can be alleviated by removing the remains of diseased plants in time after harvest and taking them out of the field for deep burial or burning. At the same time, dig deep into the soil to accelerate the decay and decomposition of the diseased body. (5) Chemical control. Start spraying at the initial stage of the disease, spray once every 7-10 days, and spray 2-3 times continuously. The medicament can be selected as 80-1000 times (75-100g / mu), 1000-fold (100125g / mu), 1000-fold (100g / mu) and so on.