Talking about the growth of green onions

The reasons for these problems are as follows:

A. The high groundwater level and poor drainage, especially in the high temperature season in the growing period and later period, are easy to cause the root of Chinese onion to swell.

B. excessive spraying of azoles will lead to plant poisoning. Therefore, the plots with relatively high terrain and good drainage should be selected before planting, and attention should be paid to reducing the excessive use of azole drugs.

02 bends

This is because the green onions are not upright and have holes, which leads to the bending of the green onions in the later stage. It is suggested to choose machine planting or artificial drilling planting.

03 pants, cracked

This is due to the rapid growth in the early stage and excessive water and fertilizer in the later stage. Choose varieties with medium growth and reduce the amount of water and fertilizer in the later stage. This phenomenon is particularly prominent in the continuous rainy days during the harvest period.

04 excessive aging

Dry tip and leaf aging are the manifestations of delayed harvest of early maturing varieties. Excessive fertility in the early stage and continuous high temperature in the later stage will accelerate or advance the aging of green onions. Varieties can be selected according to the target sales period, that is, early-maturing varieties are selected for listing, and mid-late-maturing varieties are selected for listing after the year.

05 presents tillering.

The causes of tillering in actual production are complicated. At present, the in-depth analysis of the causes of tillering is still under study, and there are two kinds of relatively recognized:

A. Usually, the climate is abnormal and changes greatly, which leads to the accelerated development of undeveloped leaf buds. Exposure to sunlight before planting or long-term drought after planting onion seedlings will also lead to an increase in tillering rate.

B. This species has the characteristics of tillering onion, and it will be easier to tiller under the influence of climate change. Methods: It is necessary to choose varieties that are not easy to tiller, and it is not advisable to expose onion seedlings to the sun for a long time after planting. After planting, it is necessary to pay attention to soil moisture and water them in time.

downy mildew

Symptoms of diseased leaves

Pedicel symptom

Onset symptoms

Leaf diseases mainly occur in the middle and lower parts, and gradually dry up and droop above the diseased parts. Sometimes only the top of the leaf gets sick, turns white and dies. False stems break and bend when they are sick. When the pedicel comes on, it presents oval lesions in the early stage, which are large, milky yellow and have white mold, and then turn pale yellow or deep purple in the later stage.

Occurrence law

A cool and humid climate is conducive to the development of pathogenic bacteria and the occurrence of diseases. The temperature is around 15℃, and it is most beneficial to get sick when there is a lot of rain. Downy mildew may be prevalent from mid-April to early May (May to June in Northeast China) when there is continuous rainfall or frequent fog and fog. land

Land with low potential, flooding, close planting and poor growth is particularly serious. The temperature is high in summer, and the illness is restrained. The incidence in autumn is also positively correlated with rainfall, and improper irrigation also induces aggravation of the incidence. In autumn, the field was seriously ill, and so was the next spring.

Preventive and control measures

① Agricultural method: choose disease resistance or mild disease. The incidence of scallions with purple stems, thin leaf tubes and thick wax powder is relatively light. Avoid crop rotation in the affected areas and implement crop rotation for 3-4 years. Maintain rural hygiene, thoroughly eradicate the sick and disabled after harvesting, and plough deeply in time. Choose a flat terrain.

The fertile loam with convenient drainage is used as seedbed and planting ground. Drainage should be done in time after rain. When the soil moisture is high, shallow tillage will disperse the water. Reasonable close planting, strengthening fertilizer and water management, eliminating diseased seedlings when planting, pulling out diseased plants in the field at an early stage and taking them out of the field for incineration.

(2) Chemical control: For spraying at seedling stage and early stage, 58% metalaxyl manganese zinc wettable powder, 64% antiviral alum wettable powder, 800% metalaxyl wettable powder or 72.2% propamocarb hydrochloride can be used for 500-700 times.

Or 800 times of 72% mancozeb wettable powder, etc. , spray every 10 day 1 time for 2 ~ 3 times continuously. There is wax powder on the leaves of green onions, so it is not easy to take medicine. In order to increase the adhesion of drugs, 5 ~ 10g neutral washing powder can be added to every 10kg liquid medicine.

purpura

Leaf symptom

Onset symptoms

Purple spot of scallion mainly harms leaves and pedicels. Most of them spread upward from the tip of the leaf and the middle of the pedicel, showing purple-brown spots or spindle-shaped concave spots. At the beginning of the lesion, it was a watery white spot, then it turned into a light brown circle or spindle, and continued to expand into brown or dark color.

Purple. When the humidity is high, the lesion is covered with dark brown or dark gray mold, which is pink and often arranged in concentric wheel patterns. The lesion continues to expand, and several lesions intersect to form long and large spots. The affected parts of leaves and pedicels are easy to soften and break, and in severe cases, a large number of leaves die.

Occurrence law

In hot and rainy summer, the disease is serious, and the optimum temperature is 25℃~27℃. The disease spread quickly during the rainy season and typhoons. Wet and rainy areas or years are often popular. In fertilizer-deficient plots, especially in the middle and late stages of fertilizer removal, the plant growth potential is weakened and the disease resistance is reduced.

The disease is getting worse. Sandy soil and drought-prone fields are early and serious. There are differences in the degree of illness among different species. The waxy layer on the leaves of red-skinned onion is thicker and the disease is lighter, while the waxy layer on the leaves of yellow-skinned onion and white-skinned onion is thinner and less, and the disease is more serious.

Preventive and control measures

① Agricultural method: choose disease resistance or mild disease. Rotation between seriously ill areas and non-onion crops. Eliminate the sick and disabled in the field in time, and plough deeply after harvest. Nurseries and planting areas should be flat and fertile, with convenient drainage. Carry out fitness training, apply sufficient base fertilizer, timely topdressing, give priority to nitrogen, and apply nitrogen, phosphorus and potassium in a balanced way to prevent fertilizer loss in the later growth stage.

② Chemical control: Spraying chemical control at seedling stage or early onset. The effective agents are 58% metalaxyl, 800 times mancozeb wettable powder, 600 times mancozeb wettable powder, 1500 times chlorpheniramine wettable powder and 600 times chlorothalonil wettable powder.

Double liquid, etc. Spray every 7 ~ 10 day 1 time, and spray continuously for 2 ~ 3 times.

gray mold

Onset symptoms

White spots appear on the leaves, and the spots are spindle-shaped to rectangular, and the diseased spots often gather into spots, which makes half or all the leaves curly and scorched. When wet, a large number of botrytis cinerea layers grow on the dead leaves, which mostly develop downward from the tip of the leaves, and the diseased spots are connected in the later stage, causing most or even the whole leaves to rot and die. The surface of dead leaves is also covered with gray mold, and sometimes black particles are produced, which are the sclerotia of pathogenic bacteria.

Occurrence law

Cold and high humidity environmental conditions are most conducive to the occurrence of gray mold. 18 ~ 23℃ is the optimum temperature for onset. In autumn, scallion can get sick at seedling stage, but it gets sick slowly in winter and spreads again in spring, reaching its peak. In winter and spring, there are many rainy days and precipitation, and the illness is serious. The number of rainy days in April-May is often the key factor affecting a large-scale epidemic. The sanitary conditions of crop rotation fields and fields are poor, leaving many sick and disabled fields, and getting sick early and seriously. Heavy soil, poor drainage, improper irrigation, excessive close planting, partial application of nitrogen fertilizer, plant weakness, trauma and slow wound healing can all lead to the aggravation of the disease.

Preventive and control measures

(1) Agricultural measures: implement crop rotation in the affected areas, and completely eradicate the sick and disabled after harvest. Take it out and destroy it. Ridge cultivation and high border cultivation can be carried out in rainy areas, and drainage can be carried out in time in rainy season to prevent water accumulation in the fields.

② Chemical prevention and control: at the initial stage of the disease, 600-900 times of 3% oxygen-rich water solution, 1200 times of 40% botrytis cinerea suspension, 800 times of 50% mirex wettable powder, 2000 times of 25% prochloraz emulsifiable concentrate, 500 times of 30% azoxystrobin wettable powder, or 50% rot.

White wilt

Leaf symptom

Onset symptoms

Also known as white tip disease. The disease can occur at seedling stage and adult stage. At the seedling stage, the diseased leaf sheaths and leaves showed dark green spots with inconspicuous oil stains, and then gradually expanded into a large area of 5 ~ 10 cm oil-soaked blue-white spots, with a white to grayish white center and gradually dry and drooping leaves. At the initial stage of the disease, most of them are at the same height, and the incidence positions of epidemic disease and gray mold are random, so these diseases can be distinguished.

Occurrence law

The pathogen mainly overwinters in the soil in the form of chlamydospores, and sporangium appears in the spring of the following year under suitable conditions, which is spread by irrigation water or wind and rain, and the newly emerging zoospores on the lesion and surface are spread by raindrops. Generally from May to June, with the arrival of the rainy season, the illness is aggravated. Rainy weather in summer is prone to disease, drainage is not timely after heavy rain, too much water and nitrogen fertilizer in the field or plants grow white.

Preventive and control measures

(1) agricultural measures: advocate rotation with non-onion, garlic and solanaceae vegetables every other year to reduce the source of disease in the field. After harvest, the sick and disabled should be eradicated in time, taken out of the field and buried or burned to reduce the source of disease in the field. Digging deep into the soil to accelerate the decomposition of the sick and disabled. Cultivate the soil in time and try to avoid the contact between onion seedlings and water. The compost fermented by enzyme bacteria should be applied with less available nitrogen to enhance the disease resistance of plants.

(2) Drug prevention and treatment: spraying drugs at the initial stage of onset, every 7- 10 days 1 time, and spraying for 2-3 times continuously. The medicament can be 72% gram green wettable powder (per mu100g) or 69% Anke manganese-zinc wettable powder (per mu100g). The growth problem of green onions has long been known and will be used for preservation.

epidemic

Leaf symptom

Onset symptoms

Leaves and pedicels are not obvious blue-white spots at the beginning of the disease, but become gray-white spots after expansion, resulting in dry leaves. When the rain is continuous or the humidity is high, the disease grows white cotton mold; When the climate is dry, the white mold disappears, and the cotton-like white mycelium can be seen when the epidermis is torn open.

Occurrence law

The pathogen is suitable for high temperature and high humidity environment, the optimum temperature is 12~36℃, and the relative humidity is above 90%. The most susceptible growth period is from adult stage to harvest stage. It is easy to get sick in rainy season; Fields with high planting density, low terrain, stagnant water in the field and excessive plant growth are seriously ill.

Preventive and control measures

① Agricultural measures: completely eradicate the sick and disabled, and reduce the source of bacteria in the field; Rotation with non-onion and garlic vegetables for more than 2 years. Choose plots with good drainage for planting, and drain them in time after rain, so as to achieve reasonable close planting and good ventilation; Formulated fertilization is adopted to enhance the disease resistance of the host.

② Chemical control: At the initial stage of the disease, spraying 60% foscarnet wettable powder 500 times, 70% ethyl manganese zinc wettable powder 500 times, 58% metalaxyl manganese zinc wettable powder 500 times, 72.2% propamocarb aqueous solution 800 times, 25% metalaxyl wettable powder 600 times and 64% emulsifiable concentrate.

verticillium wilt

Onset symptoms

At first, the scallion showed pale yellow-green variegated leaves, and the new leaves had yellow stripes or stripes of different lengths at the base. In severe cases, they were covered with leaves, and some of them were flat and twisted. Another symptom is that the leaves turn yellow, and then the whole plant is malnourished, yellow and short, with many branches and thin leaves. Onion often begins to get sick in the late stage of seedling raising, with slow growth, flat and wavy leaves, mosaic symptoms or long yellow spots, and the diseased plants are obviously short.

Occurrence law

The disease is caused by virus, which is mainly infected by aphids or field juice friction. If there is high temperature and drought in July, there will be a few typical atrophic plants in August, and the peak period is from mid-September to mid-June. Thrips and aphids in onion seedling stage are often seriously ill; The years of high temperature, drought and little rain are serious. Severe diseases caused by harsh operating conditions and neighboring Allium plants.

Preventive and control measures

(1) Agricultural measures: Carefully select onion seedlings, eliminate diseased seedlings and weak seedlings, and do not raise seedlings near onion planting fields or planting areas.

Choose plots with fertile soil to grow green onions and onions. Apply sufficient organic fertilizer and increase phosphorus and potassium fertilizer. It is necessary to apply sufficient fertilizer and topdressing in time, and planting should not be too dense, so as to facilitate ventilation and light transmission, promote growth and enhance plant disease resistance. Control thrips and aphids that spread the virus in time. Clean up the fields in time after harvest.

② Chemical control: At the initial stage of the disease, 20% virus A wettable powder was selected to be 500 times, and sprayed 1 time every1day, 2-3 times in total.