Causes and control methods of rapeseed seedling leaves purplish red

1. Boron deficiency

The rapeseed gradually turns into purple-red from the edge of the leaf, and there are also withered yellow old leaves in the field, which is most likely due to the lack of boron in the rapeseed. A further method of diagnosis is to check the root of the rape to see if it turns brown, whether the cortex is cracked, or boron deficiency. In addition, if there are obvious holes in the leaves, it may be caused by cabbage worms and leaping beetles.

Prevention and control method: Boron deficiency at the seedling stage of Camellia oleifera can be sprayed with borax 100-150 g / mu water and 25-50 kg, and sprayed again at intervals of 7-10 days. The cabbage worm can be controlled with 4.5% high-efficiency cyhalothrin emulsifiable concentrate 1500-2000 times solution, 0.3% matrine aqueous solution 500-time solution, 10% carbendazim · indenecarb 1000-1500 times solution, etc. Cypermethrin can also treat pedicel, and it can also be controlled by biphenyl thiamethoxam, imidacloprid and other drugs.

2. Freeze damage and stain damage of rape

The damage caused by rapeseed and freezing will affect the absorption of nutrients by the root system of rapeseed, resulting in insufficient phosphorus, potassium and other elements in the rapeseed plant, the synthesis of chlorophyll is less, the anthocyanin is more, and the leaves will appear purplish red. See you a lot. Symptoms in the field are excessive water accumulation and poor drainage in trenches; if aphids, jumping beetles, etc. damage the leaves, the self-protection ability of the rape is weakened, and the freezing damage will also increase. The lower the winter temperature, the more severe the freezing damage, and even dead seedlings will appear, not just the purple and red leaves.

Control methods: Drainage in time, reduce soil moisture, spray brassinolide (bihu), potassium dihydrogen phosphate, boron fertilizer, and carbendazim when the temperature rises, when the growth situation is poor, apply some fertilizer to promote rape Resume growth and prevent disease. If there are aphids, it is recommended to add acetamiprid, imidacloprid and other drugs for spraying. The prevention of freezing damage should be carried out according to the situation: if the rape is growing vigorously, it is recommended to spray Paclobutrazol and Uniconazole before the winter to control the growth and increase the resistance of the rape to low temperature. If the growth situation is poor, it is better to apply some quick-acting nitrogen fertilizer at the right time (before the small cold), it is better to add grass and ash, and enhance the cold resistance of rape. In case of sudden cooling, it is recommended to spread some ash, firewood, etc. in the rape field.

3. Rapeseed lacks boron and phosphorus

The deficiency of boron and phosphorus in rapeseed will cause the leaves of rapeseed to be purplish red, the growth will be slow, and the leaves will become smaller. Or cracked, some of the leaves will rewind, and in serious cases, the growth point will brown and die; the phosphorus deficiency of rape will not only have symptoms on the leaves, but also the petioles and dorsal veins of the leaves will be purple-red, and there will be spots or plaques on the leaf margins.

Rapeseed leaves are purple-red for various reasons. In addition to the boron deficiency, phosphorus deficiency, freezing damage, and waterlogging damage mentioned above, drought can also cause malnutrition in the root system of rapeseed, causing the rapeseed leaves to turn pale red, and sulfur deficiency can cause veins, The stems appear purple-red and the leaves turn green. You should pay attention to distinguish symptoms and prevent and treat symptoms.

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