Lettuce stem rot disease mainly starts from the petiole near the base of the stem, presenting amorphous brown necrotic spots that later spread to the entire petiole, exuding dark brown juice and causing leaf decay. The disease develops from the lower leaves to the upper parts, causing the stems to brown and rot. When the humidity is high, the disease grows a network of mycelium and brown sclerotium. If the weather is dry, the disease appears as a localized brown concave disease spot.

The prevention and control of lettuce stem rot disease should adopt a combination of agricultural technical measures and chemical control.

1. Thoroughly clearing the garden, turning over the soil, or rotating with rice before planting can reduce bacterial sources. Raise and level the border surface for irrigation and drainage purposes, and avoid flooding with excessive water. Moderately dense planting maintains good permeability in the field, reduces field humidity, increases phosphorus and potassium fertilizer appropriately, and enhances the mechanical resistance of the plant epidermis.

2. Chemical prevention and control: (1) Combined with land preparation, apply 5-8 grams of 40% pentachloronitrobenzene and Fumeishuang 1:1 on each square meter of the border surface, mix with an appropriate amount of fine soil and sprinkle it on the surface, and then mix with a hoe and surface soil for disinfection. Immediately remove diseased plants found in the field and sprinkle a small amount of medicinal soil for disinfection; (2) Mixing seeds with 40% seed weight of 0.2% can reduce seedling infection; (3) In the early stage of the disease, spray ① 20% methylribavirin emulsifiable concentrate 1200 times; ② 1500 times solution of 5% Jinggangmycin aqueous solution; ③ 50% Fumeishuang wettable powder 800 times liquid. Spray once every 7-10 days, 2-3 consecutive times.