Causes and Control Measures of Black Rot in Broccoli
Broccoli is a green, healthy vegetable; whether for the elderly or children, eating a little broccoli is good for your health. Broccoli looks similar to cauliflower, but its color is dark green. It can generally be eaten cold-tossed and is also a great ingredient for fat loss. Broccoli is grown in all regions. Recently, a grower asked why the broccoli they planted developed black rot and what control measures are available.
1. Why does broccoli develop black rot?
The pathogenic bacteria of black rot can overwinter inside seeds or in the soil along with diseased plant residues, and invade through water pores or wounds; seeds can carry the bacteria, and the pathogen can survive on seeds for about 28 months, which is one of the main ways the disease spreads over long distances. In most cases, the disease begins from the rosette stage to the head-forming stage; the pathogen spreads through rainwater, irrigation water, and farm tools, and the use of contaminated seeds or contaminated seedlings can spread it over long distances. High temperature, high humidity and frequent rain, dew on leaf surfaces and guttation at leaf margins all favor disease development; low-lying terrain, poor drainage, frequent flooding irrigation, planting too early, and years of continuous cropping with cruciferous vegetables; applying undecomposed organic fertilizer, over-applying nitrogen fertilizer, poor growth or excessive vegetative growth, root injury during cultivation, and plots with many and severe pests also develop the disease more severely; especially after heavy rainstorms, the disease can easily become epidemic.
2. What control measures are there for broccoli black rot?
1. Seedbed disinfection
Formalin may be used as the chemical. Method: use 30-40 ml of formalin per sq m of seedbed diluted in 2.5-5 kg of water, then spray with a sprayer (with the nozzle removed), turning the soil while spraying. After spraying evenly, cover with agricultural film; after one week, remove the film and turn the soil several times to allow the formalin to fully volatilize. The time required is about 5-7 days.
2. Seed treatment
Seeds can be soaked for 15 minutes in a 200-fold solution of 50% amobam aqueous solution, then washed clean, dried, and sown. Soaking seeds in hot water severely affects the germination rate of cauliflower, so it should be used with caution and avoided if possible.
3. Seedbed management
If seedling raising is done in summer, protected seedling raising must be used, with a shade net added to prevent sun scorching and heavy rain washing. After the seedlings emerge, inspect the seedlings often to ensure they are uniform and strong. If diseased seedlings appear, remove them promptly and spray chemicals for control. At the same time, throughout the seedling-raising period, control diseases and pests such as damping-off, seedling blight, and imported cabbageworm.
4. Crop rotation
Carrying out rotation with non-cruciferous vegetables for more than 2 years can basically solve the problem of soil-borne bacteria. To eliminate or reduce pathogenic bacteria in the soil, deeply plow and sun the soil for 10-20 days before transplanting, so as to speed up the decomposition of plant residues and the death of pathogens in the soil.
5. Cultivation and weeding
After seedling transplanting and recovery, apply sufficient seedling fertilizer. During plant growth, strengthen fertilizer and water management. Apply calcium, boron, and silicon fertilizers together in sufficient amounts to strengthen the plant's resistance, prevent premature aging, and enhance disease resistance. When irrigating, avoid flooding irrigation to reduce opportunities for the pathogen to spread. According to soil moisture conditions, carry out cultivation and weeding in a timely manner.
6. Pest prevention and control
In addition to causing direct losses, pests also provide a route for the pathogen to infect through wounds. Therefore, plots with many pests also have severe black rot. To prevent the disease, pests must be controlled first, especially the damage from imported cabbageworm and diamondback moth. Timely control diamondback moth, imported cabbageworm, beet armyworm, aphids, cabbage leaf beetle, root maggots, and other pests to prevent them from spreading the disease.
7. Disease prevention and treatment
After black rot center plants appear in the field, control should be carried out promptly. Control agents can include a 500-fold solution of 50% amobam, and 200 mg/kg of agricultural streptomycin, streptomycin sulfate, and phytoactin, which have obvious control effects. In addition, 50% thiophanate-methyl and 50% carbendazim wettable powder also have very good control effects.