I. Sclerotinia
The important constant diseases of rapeseed in Jiangsu Province have a great impact on the quality and yield of rapeseed. Generally, the year yield is reduced by 1-20%, and in severe years, the yield is reduced by 5-80%.
1. Occurrence of regular sclerotia left over in the soil or diseased body in the past spring germinate, release of ascospore spores spread with the airflow diffusion, as the initial infestation source, spores falling on the plant to produce hyphae, invade the aging leaves, petals Onset. The rape flowering period is generally at the beginning of the onset of disease. As the diseased petals and old leaves are reduced to other parts of the plant, lesions often form on the petiole or branches of the main stem, or are spliced ​​through the defeated leaves, resulting in stems or branches. Incidence, general before and after the final flowering period for the peak incidence of the blade and the beginning of the stem disease. The incidence of culms after the final flowering rose rapidly. The most predominant factor in the recurrence of disease is the more rainy days between the flowering stage and mature stage of rape. Continuous cropping or cruciferous crops, lettuce, etc., change the crops disease, heavy nitrogenous fertilizers, poor drainage, and severe disease caused by freezing injury. The main factor affecting the severity of sclerotinia is the flowering weather conditions. Because rape is the most susceptible, the longer the flowering period and the ascostic spore dissimilation, the heavier the disease, the more rainy and humid, the less sunshine during the flowering period, and the serious disease.
2. The field diagnosis rapeseed leaves, petioles, stems, branches, flowers, pods and other parts can be disease, the main stem of the largest incidence of loss. Usually in the lower leaves of the early spring to see disease, lesions are round or irregular shape, yellow-brown or gray, typical lesions can be seen several layers of concentric ring pattern, lesions back iron blue, field moisture can be seen when the white floc. Stems and branching lesions are fusiform or long strips, light brown water stains, gradually grayish, with high humidity the disease is soft rot, the surface of the white flocculent layer, hollow inside, later see rat manure Sclerotia, after drying, the epidermis is broken, and the fibers are exposed like hemp ropes. Petal sensation showed brown spots with oily spots. The incidence of pods was similar to that of stems and branches. The diseased part was gray and the epidermis was rough. Some diseased pods were surrounded by white mycelia and formed small sclerotia.
3. Chemical prevention and control technology The prevention and control measures of “grasping the appropriate period, taking the initiative, and using drugs in an all-round way†are taken care of when the flowering rate of the main stem is 80% to 100% and the flowering rate of the primary branch stems is about 50%. Mu with 25% carbendazim WP 150 to 250 grams, 40% sclerotin net wettable powder 100 to 150 grams, 50% procymidone (Sikron) WP 35 to 50 grams. In areas where S. sclerotiorum is resistant to benzimidazoles, S. sclerotiorum, procymidone (sulfacin), sirocacil (prochloraz), vanadin (bacetam), and enemies should be used. Force stripping (propiconazole) and other single agents and their compounding agents, such as 25% prochloraz 40-50 ml, 50% Tengyin 100 g, 25% strength drop 25-30 ml, 50% bacillus sclerotiorum (Fumei pairs + sclerotia net) 80 ~ 100 grams and so on. To use sufficient water, the amount of water per mu should be no less than 60 kg, and be thoroughly sprayed thoroughly to improve the control effect. The spraying should be done as far as possible to the lower part of the rape stalk, and the control effect is better than spraying only upwards.
Second, downy mildew
Commonly known as the "leading disease", the Yangtze River Basin is widespread. In the epidemic year, the diseased plant rate was 10% to 50%, and the yield loss exceeded 20%, which reduced the rapeseed yield and oil yield.
1. The law of occurrence is a kind of low-temperature and high-humidity disease. The temperature rises from April to May in spring to 10 to 20°C, and it is popular in wet and wet weather. Partial application of nitrogen fertilizer, low-lying terrain, poor drainage, closed fields, and persistent disease.
2. Field diagnosis of rape can occur from the seedling stage to the flowering and scab stage, and it mainly damages leaves, stems, flowers and pods. At the beginning of the disease, yellowish spots appeared on the leaves, and afterwards they expanded into irregular large spots of yellow-brown color. When the humidity was high, a white frosty mildew layer appeared on the lesions on the leaves. Stem warts, branching chlorotic spots on the onset of primary disease, after the expansion of irregular brown-brown to dark brown spots, on the frost layer of mold. After the pedicel suffered damage, it sometimes appeared swollen, curved and "headed", and the applicator turned green and swollen. There was also a layer of mold and dryness was not true.
3. Prevention and control techniques In the early spring of March, the disease period and rape twitching to the initial flowering period, when the diseased plant rate reached 10% or more, the use of drug control. 70% Mango-Manganese Zinc 100g, or 69% Dimethomorph-Manganese Zinc 100-130g, or 66.5% Propomethasone 50-75ml, or 58% Metalaxyl Manganate Zinc (Threonomycin manganese zinc) 150 to 175 grams, or 64% frost Mn-Zn (anti-mite) wettable powder 120 to 150 grams and other spray control, Amesida (azoxystrobin), ether and other agents are also relatively Good results.
Third, virus disease
Mainly caused by the spread of a variety of viruses caused by rapeseed aphids. In the early and heavy years of locust occurrence, the onset was widespread and severe.
1. The occurrence of virus is mainly transmitted by aphids, and its occurrence mainly depends on factors such as the number of aphids and climatic conditions during the growing period of susceptibility to rape (between cotyledons and 6 true leaves). In the seedling stage of rapeseed, there is a large number of winged pupa. The average monthly temperature is 15-20°C, and the relative humidity is less than 77%. The seedbed or rape field is located near the vegetable field or the field where the former pod is a vegetable is heavy, and the cabbage type is heavy. .
2. The field diagnosis of the disease is generally dwarfed, deformed, shortening stems, flowers and fruit clusters, short twisted pods, there are small black spots, and sometimes like chicken hairy claws. The symptoms of Brassica napus seedlings at the seedling stage include three types of macular, spotted and mosaic leaves. There are three types of stem spots on the adult stem: stem spot, rotenian spot, and spotted spot. The symptoms of cabbage and mustard were seedling stage, and the leaves and leaves were shrunken at the seedling stage, and the plants were dwarfed at the later stage. The stems and fruit axes shortened and the pods were deformed.
3. Prevention and control technology focuses on controlling locusts at the seedling stage. One is to use silver-grey plastic film to avoid maggots during the seedbed period, or to use the yellowishness of locusts, and to trap and kill 6 to 8 pieces of yellow plates per acre in the autumn seedbed or transplanting fields. The second is to do a good job of seed dressing. Use phoxim by mixing 2% to 3% of the seed weight and 10% to 15% of the water to mix evenly, and boring for 8 to 12 hours. Allow to dry after sowing. The third is to prevent and control locusts in a timely manner. When the amount of 100 strains in the seedling stage or in the flood season reaches 1,000 or 3,000, the pesticides are controlled by imidacloprid, acetamiprid or pyrethrin, such as 10% imidacloprid 20g or 2.5% beta-cypermethrin 2000x, 3% pyridine. Insect mites emulsifiable concentrates 40 to 50 ml, 50% anti-indoles can wet 10 to 18 grams, 2.5% cyhalothrin (Kung Fu) EC 10 to 20 ml and other spray control.
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