Symptoms of black rot of broccoli in greenhouse

At present, broccoli is mostly planted in open field, but not in greenhouse. Mainly in the process of cultivating broccoli in greenhouse, because the high temperature and humidity environment is conducive to the occurrence of diseases, especially the occurrence of black rot, once the disease occurs, the light ones will reduce the yield, and the heavy ones may lose the harvest. In view of this situation, we have done a study on the integrated control technology of black rot of broccoli in greenhouse, and now the integrated control technology is summarized as follows.

I. Identification of symptoms of black rot

The disease can occur from seedling to adult stage. The infected cotyledons of the seedlings were immersed in water, and then quickly withered or spread to the true leaves. The disease occurred in the adult stage, mainly harmful leaves, first formed from the edge of the leaves, and then expanded inward into "V" shaped withered spots. The disease spot is yellowish brown and the edge is yellowish. The roots were damaged, the vascular bundles blackened, the internal dry rot, and even the whole plant wilted and died. Bulb disease, from the spherical spot gradually spread, serious the whole flower bulb is black, rotten.

The pathogen is mainly transmitted by diseased plants, fertilizers, wind and rain or agricultural tools. The disease is easy to occur under the conditions of general seed carrying bacteria, high temperature and heavy rain, improper fertilizer and water management, continuous cropping with cruciferous crops, rampant pests and so on.

Second, the characteristics of the disease

Black rot is a bacterial disease. High temperature and high humidity are beneficial to the disease. The growth temperature of the pathogen is 5: 39 ℃ and the optimum temperature is 25: 30. C . The relative humidity is more than 95%, especially the leaf dew and leaf edge spit water, which is beneficial to the invasion of bacteria. When broccoli is cultivated in greenhouse, the environment of high temperature and humidity in the greenhouse is more conducive to the occurrence of black rot. Once the water droplets on the greenhouse film drop on the flower buds during the heading period, it is easy to cause black rot.

III. Prevention and control measures of black rot

① selected disease-resistant varieties.

② rotation was conducted with non-cruciferous vegetables for 2-3 years.

③ to strengthen cultivation management: deep drying soil, border cultivation. By drying the soil, the source of disease can be reduced. Border cultivation can dredge water in the field, reasonably close planting, do a good job of fertilizer and water management, and keep the plant healthy. When transplanting, use large and small rows to plant; adjust the temperature and humidity in the greenhouse. First of all, do a good job in seedbed management. The temperature of cultivation in early spring is low, so we should mainly pay attention to the times and amount of watering of seedling bed to prevent the occurrence of black rot. The seedling temperature of other cultivation methods is higher, especially the seedling time of winter broccoli cultivation is in mid-late August, mainly to reduce the temperature and cover the seedling bed with sunshade net.

Secondly, do a good job in post-transplanting management. Generally, it should be watered every 7-10 days after transplanting, and big fertilizer and water is needed after budding. At this time, watering times and amount of water should be increased, and a lot of ventilation should be given after each watering to reduce the humidity in the shed. Timely ventilation when the temperature in the greenhouse exceeds 25 ℃. Generally, the door of the greenhouse is opened for ventilation after 8:00 on a sunny day, and the skirt membrane on both sides of the greenhouse is opened after 9: () 0 to reduce the humidity in the greenhouse, and then all covered before and after evening. The bud stage can cover the buds with the upper leaves of broccoli before the evening of the first day to prevent water dripping on the greenhouse film in the morning.

To the buds, causing black rot. When there are no water droplets on the greenhouse film in the morning, remove the covered leaves.

At the same time, excessive drought and waterlogging should be avoided, the early diseased leaves should be removed in time, and the diseased and residual bodies should be removed completely during harvest so as to reduce the source of initial invading bacteria in the field.

④ chemical control generally starts from emergence every 10 days with 72% agricultural streptomycin soluble powder 15g + benzoiodide 2 (15mU) spray control of water 13kg, the whole growth period needs to be prevented and treated about 10 times.