Friends who have planted green onions know that the onion is the important reason for the economic benefits of green onions. There are many reasons for the dry onions. In actual production, because the vegetable farmers and distributors can not find the direct cause of the green onions, they often mismatch the medicine, which not only delays the treatment timing, but also increases the burden on the farmers.
First, the disease is dry
1, green onion gray mold
Symptoms: At first, white spots on the leaves, mostly developed from the tip of the leaf, and can extend 2-3 cm down. When the humidity is high, a large amount of gray mold is produced on the dead leaves.
Therapeutic drugs: pyrimethanil, procymidone, carbendazim, vinyl nucleus, iprodione and the like. It can be sprayed with 50% iprodione WP (Phosin 11000-1500 times solution or 50% Pythium WP (Speed ​​Kelly) 1500 times solution. 50% Pythium WP1500 times solution +% Methyl thiobacillus can be used later. Ling WP (methyl thiophanate) 500 times liquid spray control.
2, the disease
Symptoms: The affected part is blue-white and has no obvious spots. When it is enlarged, it is grayish-white spots, causing the leaves to wither from top to bottom. The field is now "dry tip"; when the humidity is high, the ministers are sparsely white, and when the weather is dry, the white mold disappears. . The inner wall of the long conical leaf is examined and the white mycelium is visible, which is different from the physiological "dry tip" of the onion.
Therapeutic drugs: azoxystrobin, fenhexamide, enoylmorpholine, flumorph, triethylaluminum sulphate, propamocarb, manganese zinc, frost urea, chlorothalonil, antivirus sputum.
3, downy mildew: the leaves are damaged, began to produce oval or oval lesions, initially yellow-white, then turned gray-white. When the humidity is high, the surface of the lesion is white with a thin layer of mildew. In the early stage of the disease, 40% ethylphosphorus aluminum WP400 times solution can be used. In the later stage of the disease, 72.2% of the mildew AS can be used (Pulke 1600-800 times liquid or 72% manganese zinc · frost urea WP (Klu) 600-800 times liquid, 40 % ethyl phosphorus aluminum WP + 64% anti-virus 矾 WP400-600 times liquid spray control.
4, root rot
The green onion leaves are yellow and then atrophied and dead. The roots and stems become black and rot, and the roots gradually necrosis, eventually leading to dead seedlings and dead trees. In general, after rooting at the time of planting, after flooding with large water after planting, there is a lot of rain, and when it encounters hot weather, the incidence is heavy.
Therapeutic drugs: carbendazim, metalaxyl, thiram, methyl chlorpyrifos, sodium chloroacetate, iodine, copper preparations, etc.
Second, the physiological dry tip
1. The acid soil hazard causes the dry-point neutral soil to be suitable for the onion length of the onion, which is most suitable for pH 7.0-7.4. When the application of organic fertilizer is less, the application of ammonium sulfate and superphosphate will cause acidification of the soil, causing slow growth of the onion leaves, and the outer leaves are yellow. Control measures: Apply enough decomposed organic fertilizer per acre and apply 150 kg of calcium oxide (CaO).
2, drought caused by the cultivation of dried onion, do not pay attention to watering, soil drought, plant water shortage easily lead to dry tip. Control measures: According to the different needs of different growth stages of onion, watering should be timely and appropriate. Appropriate water control in the seedling stage, do not dry or not, 15-20 days to pour a small water; nutrient growth period combined with topdressing, soil and timely watering to ensure sufficient water supply, so that the field water holding capacity is maintained at 70%-80%; before harvest Control watering for 10-15 days to keep the field water holding capacity at 60%-70%.
3, the lack of trace elements caused by the dry tip of calcium deficiency, the dry tip of the heart, yellowing, developmental resistance, lack of magnesium external leaf tip yellowing. Control measures: It can be applied to the roots, such as 0.1%-0.3% calcium nitrate (ca(NO3)3), 0.1% magnesium chloride (MgCl2).
4. The growth temperature range of dried scallions caused by high temperature and freezing damage is 7-35 ° C. When the temperature exceeds 35%, the tip of the leaf is dry. Below 7 ° C, the tip of the blade turns white after the cold tip is cold damaged. Control measures: Pay attention to the watering and cooling of the green onions cultivated in the open field; strengthen the wind in the greenhouse cultivation, prevent the high temperature above 30 °C, and strengthen the heat preservation so that the minimum temperature is not lower than 7 °C.
5. The toxic gas hazard caused by the application of ammonium sulfate ((NH4)2SO4) or ammonium chloride (NH4C1) in the closed state of the tip, which will cause ammonia gas hazard, and the acidification of the soil will cause harm to the nitrous acid gas. The ammonia hazard causes the tip of the blade to wither and gradually turns brown; the nitrous acid gas damages the tip of the leaf and becomes white and dead. Control measures: First, release the wind; second, increase the application of organic fertilizer, if the air can not be vented, do not pursue ammonium carbonate; third, use Guoguanggenbao or Sanjuan irrigating solution to dissolve the root or spray to remove the hazard, the specific usage is 500 times liquid is irrigated once, sprayed with 1000 times liquid, once every 7 days, even sprayed twice, the control effect can reach 100%.
6, the phytotoxicity caused by the concentration of dry tip agents is too high, so that the tip of the leaves become white, dry. The prevention and control measures are to control the concentration of the chemical solution. Spraying 0.05% of the nucleotide solution 500 times can relieve the damage, or spray 500-800 times of Jiameijin point in the morning or evening, once every 7 days, even spray 2-3 times, the control effect can reach 100%.
Third, the hazard of the fly causes the dry tip
1, the symptoms of the fly larvae into the roots of the onion damage caused by the dry top of the tip of the leaves dry, pull up the onion to see the onion roots turn brown, severely rot or die.
Control method: In the adult stage, use 2.5% deltamethrin EC 3000 times solution, spray at 9-11 am, spray once every 5 days, even spray 2-3 times. When the larva hatching peak and the larvae of the larvae occur, the sooner the better, the better, you can use 40% chlorpyrifos 800-1000 times liquid or 50% phoxim emulsifiable oil 500 times solution to fill the roots, every 7-10 days, even Iot 2-3 times.
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