Causes and Control Methods of Soft Rot in Lotus Root, Lettuce, and Romaine Lettuce
Lotus root, lettuce, and romaine lettuce are three crops prone to soft rot during production. So what are the causes? What control methods are there? Let's take a look together below.
I. Causes and Control Methods of Lotus Root Soft Rot
Causes:
1. It is a fungal disease that mainly attacks the underground stem of lotus root, causing it to turn brown and rot, and leading to the wilting of the above-ground parts.
2. In the early stage of damage to the underground stem, symptoms are not obvious; later, irregular brown spots appear on the diseased stem, lotus rhizome, and roots. When the diseased stem is cut open, the vascular bundles at the center show browning.
3. The leaves of affected plants become lighter in color, then water-soaked wilting appears at the leaf margins, and finally the entire leaf curls and dies. The pathogen overwinters as mycelium in seed lotus roots or in the soil. Infected seed lotus roots and field plots are the main primary sources of infection for this disease.
Control methods:
1. In old lotus root areas, promptly dispose of plant residues. Except for fields where seed lotus roots are retained, after harvest, promptly cut down the remaining lotus stems and burn them in a centralized manner; after harvest, the lotus root field can be planted with one season of winter crops. For fields not planted with overwintering crops and fields without water sources, deep plowing and sun-drying of the soil should be carried out in winter. Where water sources are good, the fields can be flooded in winter, as pathogens have difficulty overwintering in flooded fields in winter.
2. Lime treatment: before the first plowing, evenly broadcast 100-150 kg of quicklime and 25-30 kg of lime nitrogen per mu, then plow deeply into the soil. This not only provides fertilization but also helps adjust soil pH and disinfect, effectively killing many pathogenic bacteria.
3. Select disease-free seed-production fields, which can avoid pathogen carriage in seed lotus roots and reduce the primary infection source.
4. Disinfect seed lotus roots: after the seed lotus roots are dug up, soak them for about 10 hours in a 1000-fold solution of 33.5% copper quinolate plus an 800-fold solution of 70% thiophanate-methyl wettable powder, then remove, air-dry, and plant; alternatively, spray the seed lotus roots with the above agents, cover with plastic film, seal for 24 hours for fumigation disinfection, air-dry, and plant.
5. Crop rotation: alternate-year rotation between flooded and dry conditions is best; generally, continuous cropping should not exceed 3 years. Flooded-dry rotation can purify the soil, reduce pathogen accumulation, regulate soil nutrients, improve soil structure, and enhance disease resistance.
6. Apply sufficient decomposed organic fertilizer and topdress in a timely manner. Topdressing should combine nitrogen, phosphorus, and potassium fertilizers, and also supplement molybdenum, zinc, boron, and other trace element fertilizers.
7. In the early stage of disease onset, promptly pull out diseased plants. Per mu, mix 500 g of 50% carbendazim + 75% chlorothalonil wettable powder with 50 kg of fine soil, mix well, pile and compost for 3-4 hours, then broadcast in shallow-water lotus root fields, and at the same time spray the leaves with a 1000-fold solution of 50% prochloraz, once every 7-10 days, for 2-3 consecutive applications. Alternatively, in mid-June, drain the lotus root field, irrigate the soil around the lotus root crowns with a 600-fold solution of dexon, refill with water the next day, once every 5-7 days, for 4 consecutive sprays.
II. Causes and Control Methods of Lettuce Soft Rot
Causes:
1. The pathogen overwinters on diseased plant residues or inside seeds. The following year, it invades through stomata on seedling leaves, water pores at leaf margins, or wounds. After bacterial invasion, it forms a systemic infection.
2. Long-distance spread mainly occurs through seeds, while in the field it spreads via rainwater, insects, and fertilizer. Disease is more likely under high temperature and high humidity conditions. Fields that are low-lying, continuously cropped, or heavily damaged by pests have more severe disease.
Control methods:
1. Carry out crop rotation with allium and grass family crops for more than 2-3 years.
2. Apply compost fermented with Japanese enzyme bacteria. Select disease-free seeds, drain promptly after rain, and pay attention to controlling underground pests.
3. At the early stage of disease onset, begin spraying 30% copper oxychloride suspension concentrate at 800-fold, or 30% Ludebao suspension concentrate at 300-400-fold, or 50% copper succinate-glutarate (DT) wettable powder at 500-fold, 70% copper succinate-glutarate middot; fosetyl-aluminum (DTM) wettable powder at 500-fold, 25% thiacloprid wettable powder at 500-1000-fold, 72% agricultural streptomycin sulfate at 3500—4000-fold, 47% Kasumin wettable powder at 1000-fold; spray 50 L of the prepared solution per 667 m2, once every about 10 days, for 1 or 2 treatments. Stop applying the pesticide 3 days before harvest.
III. Causes and Control Methods of Romaine Lettuce Soft Rot
Causes:
1. The pathogen overwinters on diseased plant residues or inside seeds. The following year, it invades through stomata on seedling leaves, water pores at leaf margins, or wounds. After bacterial invasion, it forms a systemic infection.
2. Long-distance spread mainly occurs through seeds, while in the field it spreads via rainwater, insects, and fertilizer. Disease is more likely under high temperature and high humidity conditions. Fields that are low-lying, continuously cropped, or heavily damaged by pests have more severe disease.
Control methods:
1. Carry out crop rotation with allium and grass family crops for more than 2-3 years.
2. Apply compost fermented with Japanese enzyme bacteria. Select disease-free seeds, drain promptly after rain, and pay attention to controlling underground pests.
3. At the early stage of disease onset, begin spraying 27% copper hydroxide suspension concentrate at 600-fold, or 30% Ludebao suspension concentrate at 300-400-fold, or 50% copper succinate-glutarate (DT) wettable powder at 500-fold, 70% copper succinate-glutarate·fosetyl-aluminum (DTM) wettable powder at 500-fold, 25% thiacloprid wettable powder at 500-1000-fold, 72% agricultural streptomycin sulfate at 3500-4000-fold, 47% Kasumin wettable powder at 1000-fold; spray 50 L of the prepared solution per 667 sq m, once every about 10 days, for 1 or 2 treatments. Stop applying the pesticide 3 days before harvest.