Comprehensive control of black spot of broccoli

The morphological characteristics and growth habits of broccoli are similar to those of common cauliflower (cabbage). It belongs to Brassica campestris and 1-2-year-old herbaceous plants. Strong growth, heat resistance and cold resistance are strong. The plant is tall, about 20 flower stems are drawn out according to the leaf growth of different varieties, and the apical buds are grouped. Closely clustered into a flower ball, the shape is hemispherical, the bud is turquoise, so it is called broccoli.

Growth habits of broccoli

Lighting requirements: broccoli is not very strict in light requirements, but in the growth process like sufficient light, when the plant growth is strong, can form a strong nutrient, conducive to photosynthesis and nutrient accumulation, and make the bouquet compact and compact, bright green color and good quality, too strong sunshine in midsummer is also not conducive to the growth and development of broccoli.

Temperature requirement: in the range of 5 ℃ and 20 min, the higher the temperature, the faster the growth and development of broccoli. The optimum temperature for germination was 20 ℃, and the optimum temperature for growth at seedling stage was 15 ℃. Broccoli has strong cold and heat tolerance, the suitable temperature for growth at rosette stage is 20 ℃ 22 ℃, and the suitable temperature for flower head development is 15 ℃ 18 mol. When the temperature is higher than 25 Mel, the quality of flower head is easy to deteriorate, but as long as it is not damaged by freezing, it can still grow slowly at low temperature of 5 ℃ or below. There are great differences in temperature requirements for vernalization among different varieties and seedling ages, so the selection of varieties in annual cultivation is very important.

Water requirement: broccoli needs more water in the whole growth process, especially in the period of vigorous leaf growth and flower head formation, even if it is short-term drought, it will reduce the yield. Rainy or high soil moisture at seedling stage can easily cause diseases such as black rot and black spot. During the period of flower head formation, the soil moisture and field capacity are about 70% and 80% in order to meet the growth needs.

Soil requirements: broccoli is not strict on soil conditions, but too barren will lead to poor plant development, low yield and quality, and over-fertile soil will lead to loose buds and hollow moss. Broccoli is suitable to be planted on loam and sandy loam with good drainage and irrigation, deep plough layer, loose and fertile soil and strong water and fertility conservation. The range of soil PH was 5.5 Mel 8, but 6 was the best. Broccoli needs sufficient fertilizer during the whole growth process, and its ratio of N, P and K is 14:5:8. The demand for nitrogen was relatively high at the seedling stage, and the demand for P and K was relatively increased after flower bud differentiation.

It is noted that boron, molybdenum, magnesium and other trace elements are also needed in broccoli during the development of the corm, so the application of appropriate trace element foliar fertilizer before budding will significantly improve the yield and quality.

Comprehensive control of black spot of broccoli

Symptoms of black spot of broccoli:

Black spot of broccoli, also known as pseudo-black spot, is mainly harmful to leaves, flowers and pods. Leaves infected with almost black round with concentric wheel spots, diameter 1 to 10 mm, wheel pattern is not obvious, but the black mold on the disease spot is often more and more obvious than Chinese cabbage, when the disease spot is more, the disease spot fuses into large spot, the leaf yellowing and early withering; stem and petiole disease spot is longitudinal strip, with black mold; pedicel, seed pod dye black brown long fusiform strip spot.

The pathogen of black spot of broccoli:

Alternariabrassicicola (Schw.) Wiltshire. It is called Alternaria brassica, which belongs to semi-known fungi. Fungi grow on both sides of leaves, dark olive to dark light brown, valvular; conidiophores olive brown, size 70 × 5 ~ 8 microns; conidia are more than 20 chain, sometimes branched, light to dark olive brown, with transverse septum 1 × 11, mediastinal few, size 18 ~ 130 × 8 ~ 20 microns. Besides, Alternaria oleracea M.Ibrath is also the pathogen of the disease.

Transmission routes and incidence conditions of black spot disease of broccoli:

The pathogen overwintered on the diseased body, seed collecting plant and soil, and infected broccoli when the conditions were suitable. After the disease, the conidia produced by the disease were transmitted by wind and rain in the field for many times. Generally, after rain, the temperature is 25: 31 ℃, the incubation period is short, the disease is easy to occur, and the disease is serious due to lack of fertilizer, weak growth and poor management.

Comprehensive control methods of black spot disease of broccoli:

1) rotation with non-cruciferous vegetables, using monopolized cropping or high-border cultivation, timely drainage after rain, strict prevention of moisture retention.

2) clear the sick and residual body in time after harvest, turn deeply in time, adopt the technology of formula fertilization, properly control watering and increase the application of phosphorus and potassium fertilizer when the seed ball grows to fist size. Such as topdressing calcium superphosphate, plant ash, bone powder, etc., can enhance disease resistance.

3) when the bulb of the remaining plant grows to 2pm 3, cut off the part that is not easy to be extracted in the middle, leaving only 3 flower branches next to it, and spray 65% Daimen zinc wettable powder 500 times as much liquid at the incision as antiseptic.

4) focus on ecological control when planting broccoli in protected areas and plastic sheds. When planting in early spring, there is a large temperature difference between day and night, 20: 25 ℃ during the day and 12: 15 ℃ at night, and the relative humidity is as high as 80%, which is easy to dew, which is conducive to the occurrence and spread of the disease. Emphasis should be placed on adjusting the temperature and humidity in the shed, especially in the early stage of planting, the stuffing time should not be too long, the humidity in the shed should be too high and the temperature should be too high, so as to achieve the organic cooperation of water, fire and wind to slow down the spread of the disease. If the dust method is used to spray 5% chlorothalonil dust at the initial stage of the disease, 667 square meters of 1kg, once every 9 days, continuous prevention and treatment for 3 times. You can also use 45% chlorothalonil smoke remover or 15% carbendazim smoke agent, 667 square meters, 200 grams 250 grams. Smoke all night.

5) before the onset of the disease, 50% prohydantoin wettable powder 1000-1500 times or 75% chlorothalonil wettable powder 600 times and 80% spray gram wettable powder 600 times were sprayed in the open field or shed. The key to the control effect of the above protective agents lies in the use of the drugs sooner or later. For those who start spraying prevention without seeing the disease spot before the onset of the disease, the control effect is more than 70%. Although the drug has a certain inhibitory effect after the onset of the disease, it is not ideal. Therefore, it is emphasized that the prevention and control should be started before the onset of the disease, the source of bacteria should be depressed, and the disease should be controlled below the index of economic damage. Stop using medicine 7 days before harvest.