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, and what control methods are available? Let's take a look below.
I. Causes and Control Methods of Lotus Root Soft Rot
Causes:
1. It is a fungal disease that mainly infects the underground stem of lotus root, causing it to turn brown and rot, and leading to wilting of the aboveground parts.
2. Symptoms in the early stage of infection on the underground stem are not obvious. In the later stage, irregular brown spots appear on the diseased stem, lotus rhizome, and roots. When the diseased stem is cut open, the vascular bundles in the center show browning.
3. The leaves of affected plants become lighter in color, followed by water-soaked wilting 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 fields are the main primary sources of infection for this disease.
Control methods:
1. In old lotus root growing areas, deal with residual plants in time. Except for fields kept for seed lotus roots, after harvest, cut down the residual lotus stems in time and burn them in a centralized manner. After harvest, the lotus root field can be planted with one season of winter crops. Fields not planted with overwintering crops and fields without water sources should be deep plowed and sun-dried in winter. Where water sources are good, the fields can be flooded in winter, as the pathogen can hardly overwinter in flooded fields in winter.
2. Lime treatment. Before the first plowing, evenly spread 100-150 kg of quicklime and 25-30 kg of calcium cyanamide per mu, then plow deeply into the soil. This not only provides fertilizer but also helps adjust soil pH and disinfect the soil, effectively killing many pathogenic bacteria.
3. Choose disease-free fields for seed retention, which can avoid seed lotus roots carrying the pathogen and reduce the primary infection source.
4. Disinfect seed lotus roots. After the seed lotus roots are dug up, soak them in a solution of 33.5% copper quinoline at 1000 times dilution plus 70% thiophanate-methyl wettable powder at 800 times dilution for about 10 hours. Remove, air-dry, and then plant. The above agents can also be sprayed on the seed lotus roots, followed by covering with plastic film and sealing for 24 hours for fumigation disinfection. Air-dry and then plant.
5. Crop rotation. Alternate paddy and dryland cropping every other year is best. Generally, continuous cropping should not exceed 3 years. Paddy-dryland 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 trace fertilizers such as molybdenum fertilizer, zinc fertilizer, and boron fertilizer.
7. In the early stage of the disease, pull out diseased plants in time. Mix 500 g of 50% carbendazim + 75% chlorothalonil wettable powder with 50 kg of fine soil per mu. After mixing well, compost for 3-4 hours and broadcast it in the shallow-water lotus root field. At the same time, spray the leaves with 50% prochloraz at 1000 times dilution, once every 7-10 days, for 2-3 consecutive times. Alternatively, in mid-June, drain the lotus root field and drench the soil around the lotus root crowns with dexon at 600 times dilution, then reflood 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 residues or inside seeds. The following year, it invades through stomata, water pores at leaf margins, or wounds on seedling leaves. After bacterial invasion, it forms a systemic infection.
2. Long-distance spread mainly occurs through seeds. In the field, it spreads through rain, insects, and fertilizer. The disease occurs easily under high temperature and high humidity. Fields that are low-lying, continuously cropped, or heavily affected by pests have more severe disease.
Control methods:
1. Carry out crop rotation with allium crops and grass family crops for more than 2-3 years.
2. Apply compost fermented with Japanese enzyme bacteria. Use disease-free seeds, drain water promptly after rain, and pay attention to controlling underground pests.
3. In the early stage of the disease, begin spraying 30% copper oxychloride suspension at 800 times dilution, or 30% Lvdebao suspension at 300-400 times dilution, or 50% copper bis(dodecylbenzenesulfonate) (DT) wettable powder at 500 times dilution, 70% DT (DTM) wettable powder at 500 times dilution, 25% thiacloprid wettable powder at 500-1000 times dilution, 72% agricultural streptomycin sulfate at 3500—4000 times dilution, or 47% Kasugamycin copper wettable powder at 1000 times dilution. Spray 50 L of the prepared solution per 667 m2, once every about 10 days, for 1 or 2 treatments. Stop using the chemicals 3 days before harvest.
III. Causes and Control Methods of Romaine Lettuce Soft Rot
Causes:
1. The pathogen overwinters on diseased residues or inside seeds. The following year, it invades through stomata, water pores at leaf margins, or wounds on seedling leaves. After bacterial invasion, it forms a systemic infection.
2. Long-distance spread mainly occurs through seeds. In the field, it spreads through rain, insects, and fertilizer. The disease occurs easily under high temperature and high humidity. Fields that are low-lying, continuously cropped, or heavily affected by pests have more severe disease.
Control methods:
1. Carry out crop rotation with allium crops and grass family crops for more than 2-3 years.
2. Apply compost fermented with Japanese enzyme bacteria. Use disease-free seeds, drain water promptly after rain, and pay attention to controlling underground pests.
3. In the early stage of the disease, begin spraying 27% copper hydroxide suspension at 600 times dilution, or 30% Lvdebao suspension at 300-400 times dilution, or 50% copper bis(dodecylbenzenesulfonate) (DT) wettable powder at 500 times dilution, 70% DT · fosetyl-aluminum (DTM) wettable powder at 500 times dilution, 25% thiacloprid wettable powder at 500-1000 times dilution, 72% agricultural streptomycin sulfate at 3500-4000 times dilution, or 47% Kasugamycin copper wettable powder at 1000 times dilution. Spray 50 L of the prepared solution per 667 sq m, once every about 10 days, for 1 or 2 treatments. Stop using the chemicals 3 days before harvest.