This year is the year of El Nino. China's South China region experienced an exceptionally large arid climate in 54 years. It is expected that most of the temperature will fall below 20°C from December of this year to February of the next year, and the relative humidity will be less than 50%. Insect reproduction and prevalence, relatively few occurrence of pests, the occurrence of a shrinking area, the degree of decline. However, some experts pointed out that the occurrence of vegetable virus disease in southern China has been more serious this year than in previous years. Powdery mildew and wilt disease have been severe in some areas. Large numbers of roundworms have occurred, and fleas, diamondback moths, cabbage caterpillars, and spotted fly flies have become lighter. 1. Powdery mildew mainly affects southern pea crops. 1, symptoms of peas can be the entire growth period, the incidence of the main parts of the leaves, petiole, stem and axillary times. At the beginning, the front or back of the leaf had small spots of chlorosis and pale yellow; the spots gradually expanded into irregular patches around the site with a small amount of white powder; the lesions were yellow and the surface was covered with white powder. In severe cases, the entire leaves, stems and pods were covered with white powder, and the leaves were withered and plants died. 2. Occurrence of the condition Powdery mildew is the pathogen of the powdery mildew. It belongs to the special parasite and can only survive on living organisms. There is no overwintering phenomenon in the southern part of China. The conidiospores of pathogenic bacteria are mainly transmitted by airflow. The suitable temperature for the growth of pathogens is 15-25°C, and the humidity does not affect the humidity. Many diseases and residues in the fields, warm nights and cold weather, dense planting, and partial application of nitrogen fertilizers are likely to form a large area. 3. Prevention and cure method 1 Rotation: It is best to use crop rotation, followed by non-bean and non-cucurbit crop rotation. Remember not to continue cropping with peas (because pea rhizobium secretions remain in the soil and affect the growth of peas.) 2) Selection of disease-resistant varieties: At present, safflower and leaf peas are resistant to powdery mildew; 3 Management: rational close-packing, application of organic fertilizer, use of three-component compound fertilizer as top dressing, and enhancement of plant disease resistance; 4 Seed Dressing: Uniform Mixing with 2.5% Seed Suspension with a seed mass of 0.3%, or 75% of dextran wettable powder, or 70% thiophanate-methyl wettable powder, or 50% carbendazim apparent powder Seed sowing 24 hours after sowing; 5 Leaf picking: timely removal of old leaves and diseased leaves in the lower part and burning, increase ventilation and light transmission and reduce the source of the disease; 6 spraying: early stage of disease, spraying 12.5% ​​to get the EC (powder rust) Rikke) 3000 times, or 75% of Dikekon wettable powder 600 times, or 20% triadimefon EC 1000 times, or 50% polysulfide suspension 600 times, spray once every 10 days, pay attention Rotation medication. 2. Fusarium wilt mainly damages winter melon crops, causing the crops to grow very slowly. The whole plant withered and died. 1, the symptoms of seedling stage and plant stage can be pathogenic bacteria invade the roots, but the leaves, stems and roots can show symptoms. At the seedling stage, young leaves lose water and wilt, and their growth stops and they die. 1 Leaf symptoms in the middle and late stages: During the daytime, the leaves from the bottom or the side of the plant gradually become water-loss from the bottom to the top, the water loss at high temperature is more obvious at noon, and it can return to normal at night, and can not return to normal after a few days. The color gradually changed from brown to yellow, and later leaves yellowed and died; 2 stem symptoms: yellow lesions, longitudinal stripes, and sometimes cracking and flowing out of the brown glial pus, no odor, the browning tube becomes brown; 3 Root symptoms: The main root becomes brown, and the surface is rough and cracked, rot, and then the lateral roots are also rot and rot, the vascular bundles turn brown, and when the humidity is high, red mouldy material grows on the surface of the diseased part. 2. Occurrence conditions Fusarium wilt pathogens are mainly soil-borne pathogen Fusarium oxysporum. Conidia are sickle-like and live for many years in the soil with mycelia, conidia, chlamydospore, or sclerotia. Tissue or seed propagation, pathogens suitable for soil temperature 8-30 °C, the influence of air humidity is small, but the continuous rain and rain caused poor crop resistance and susceptible to disease. 3, prevention and control methods rely on prevention to control, once the disease, vascular bundle system is damaged, it is difficult to control. 1 Selection of disease-resistant varieties: After study, there are 7 different physiological specialization types of pathogenic bacteria, and the specialization type is strong, so we must choose the corresponding disease-resistant varieties in the local area; 2 selection and rotation: choose well-drained, rich organic matter , Previously cultivated as a non-legume, non-melon crop land; 3 Soil sterilization: If the previous crop had blight, use 95% hymexazide wettable powder 3000 times, or 40% pentachlor, before planting. Nitrobenzene wettable powder 1000 times liquid drenching or leaching; 4 seed disinfection: As the seeds with a large number of pathogens, before sowing with 50-55 °C warm water invade 30 minutes, or 75% chlorothalonil WP 500 times Soaking for 5 hours, remove and wash with water, germination sowing; 5 low temperature when covered with a small arch shed, so that seedlings grow robustly, improve disease resistance; 6 Grafting disease prevention: can fundamentally prevent the occurrence of blight. The results showed that the use of Yunnan Black-skinned squash seedlings as rootstocks and melon seedlings resistant to other diseases as scion could achieve both the resistance to wilt disease and other diseases, but the affinity of rootstocks and scions must be noted;7 Lime disinfection: The diseased plants were found to be brought out of the field and burned in time, and were disinfected with lime in the diseased points; 8 Chemical control: After transplanting, the disease was prevalent with 23% of the Gram-negative water solution 500 times, or 50% more Diosperm wettable powder 1500 times, or 95% hymexazide wettable powder 2000 times Irrigation roots, irrigation intervals of about 20 days, a total of 4 times. Other pests and diseases that occur from December to February are virus disease, root rot, aphids, flea beetles, diamondback moth, cabbage caterpillars, and leafminers. (Guangdong Academy of Agricultural Sciences Li Renke Ke Huanan South Agricultural University, College of Resources and Resources, Rao Xueqin)
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