Why does the onion appear yellow and dry? Main points of onion yellowing and drying
Onion is one of the most common vegetables in our life. Because of its high nutritional value and good planting efficiency, it can be said to have become the main crop. However, with the continuous expansion of onion planting area, the onion yellowing phenomenon has increased year by year, and the serious plot is as high as 80%, which directly affects the onion yield and quality improvement, which restricts the value-added. Therefore, today Xiaobian talks about the causes and prevention points of onion yellowing, as follows.
First, the disease causes yellowing and dryness
1, fungal diseases
(1) There are mainly gray mold, downy mildew and purple spot disease.
(2) Control points: select disease-resistant varieties, select disease-free plants for seed collection; seed treatment before sowing, soak seeds for 30 minutes with warm water; avoid rotation for more than 2 years; strengthen fertilizer and water management, pay attention to remove diseased bodies; 7 to 10 days spraying once, downy mildew can choose 77.2% Plex 800 times solution, 64% antivirus WP WP 500 times solution, 80% strong WP 500 times solution; gray mold can choose 50% Suo Ke Ling WP 1500 ~ 2000 times liquid, 50% phlegm WP 1500 ~ 2000 times liquid; Purple spot can choose 64% antivirus WP WP 500 times or 50% phlegm WP 1500 Double liquid.
2, bacterial diseases
(1) Mainly onion soft rot.
(2) Prevention and control points: avoid continuous cropping, pay attention to eliminate underground pests; avoid spreading to the heart leaves when topdressing; avoid flooding when watering; use 72% agricultural streptomycin soluble powder 3000 times liquid or 58% synergistic ruthenium 600 times liquid control.
Second, pests cause yellowing and dryness
1. When the onion is seriously damaged by the larvae (mantle), red spider, and thrips of the fly, it is yellowed, the leaves are twisted, and the leaves are dry.
2, prevention and treatment points
Application of decomposing fertilizer, trapping adult flies; adults can choose 2.5% high-grade cyanide vinegar 2000 times solution, or 20% chrysanthemum emulsifiable oil 3000 times solution, larvae can be rooted with 50% phoxim 800 ~ 1000 times solution. Anti-red spider can be controlled with 73% gram of 2000-3000 times liquid or 20% 螨 星 star milk 1500 ~ 2500 times.
Third, physiological yellowing and dryness
1. Drought
Key points for prevention and control: increase the application of organic fertilizer; according to the water requirement of different growth stages of onion, timely and appropriate watering; ensure sufficient water in the nutrient growth period.
2. Soil acidity hazard
Control points: increase the application of organic fertilizer; reduce the application of acid fertilizer.
3, high temperature and freezing damage caused by yellowing
Control points; watering should be cooled in case of high temperature; pay attention to prevent low temperature freezing damage.
4, phytotoxicity caused by yellowing and dryness
Control points: scientifically grasp the concentration of the drug, reasonable ratio; spray evenly when spraying; can produce 0.05% green wind 95 when the phytotoxicity occurs, 500 times liquid or 500 times liquid potassium dihydrogen phosphate.
For the wonderful pictures and popular comments on the prevention and treatment of onion yellowing, you may be interested in the following recommended contents. Welcome to read.
Plant Support,Plant Spiral Wire,High Quality Twine Wire,Tomato Spiral Stake
JIANGSU SKYPLAN GREENHOUSE TECHNOLOGY CO.,LTD , https://www.greenhousehydroponic.com