The leaves of watermelon turn yellow after transplanting.

The yellowing of watermelon leaves after transplanting may be caused by the use of immature human and animal dung, long-term heavy use of chemical fertilizer, plant deficiency of potassium, calcium, boron, improper use of herbicides, harm of red spiders and so on. Therefore, when using fertilizers and herbicides, we must master the quantity and skills, and prescribe the right medicine for the disease in time.

Causes and control methods of yellowing leaves of watermelon after transplanting:

First, yellow leaves caused by improper burning of roots with fertilizer

Due to the use of immature human and animal manure, or the long-term use of a large number of chemical fertilizers, resulting in fertilizer damage to the roots. Some use foliar fertilizer too much, because many foliar fertilizers contain hormone substances, resulting in watermelon hormone and micro-fertilizer poisoning, making leaves ossified, chlorotic, brittle, deformed and yellowed.

Prevention and control methods:

1. It is strictly forbidden to use unripe human and animal dung. Chicken and cow dung must be fully fermented and cooked in advance before it can be used.

two。 When using chemical fertilizer, it is best to adopt formula fertilization, properly increase the application of phosphorus and potassium fertilizer, and when applying base fertilizer, nitrogen fertilizer should not be used too much to prevent nitrogen from burning roots.

3. When it is found that fertilizer burns roots, microbial agents should be applied in time, 5-10 kg per mu, along with the water. For the rotten roots and yellow leaves of watermelons planted in the greenhouse caused by the use of raw dung, the method of membrane-breaking ventilation should also be adopted to reduce air damage.

Second, yellow leaves caused by herbicides

Post-seedling herbicides are generally used in watermelon fields, and the operation sequence should be strictly mastered when transplanting, ridging and spraying herbicides on the flat ground, and then digging holes for planting. In this way, the herbicide layer on the soil surface can be opened when planting, so as to avoid damage to the root system of watermelon. When planting watermelons in a small arch shed in the north, double film should be used as far as possible when using herbicides, that is, one layer of plastic film and one layer of arch shed. In this way, the plastic film can effectively press the smell of herbicide transpiration under the film and will not affect the growth of watermelon. For the planting mode of dual-use of one film, that is, the planting mode of plastic film in the early stage and the later stage of the arch shed, the use of herbicides should be very cautious. In a closed environment, water vapor transpiration and herbicide fumigation will inhibit the growth of watermelon seedlings and yellowing leaves.

Control method: timely ventilation, and per mu with gold microorganism agent 5 kg irrigation root, and then watering, yellow leaves can gradually turn green.

Third, yellow leaves caused by element deficiency

In recent years, due to the good planting efficiency of watermelon, the phenomenon of continuous cropping of watermelon is more prominent, which is easy to cause element deficiency. The more common watermelons are potassium deficiency, calcium deficiency and boron deficiency, which are easy to cause different degrees of yellow leaves of watermelon.

Prevention and control methods:

1. Try not to continue cropping.

two。 For continuous cropping watermelon, 50 kg of Shenliu54 mineral fertilizer can be added per mu to supplement the deficiency of trace elements while nitrogen, phosphorus and potassium fertilizer are used. For watermelon seedlings with symptoms of element deficiency, 300 times of compound microbial fertilizer or 350 times of gold and micro multi-purpose solution + 500 times of Indian calcium can be sprayed, which has an obvious effect on preventing the symptoms of element deficiency of watermelon.

4. Yellow leaves caused by soil salt damage

Soil salt damage mostly occurred in greenhouse watermelon shed, and open field watermelon mostly occurred in continuous cropping plots. Long-term use of chemical fertilizer or excessive use of chicken, cow, duck manure, salt damage is often more serious. The surface of the heavily salinized soil will generally turn white and red, and the watermelon growing in the salinized soil will show slow plant growth, dwarfing, dark green leaves and dehydrated edges on the leaf edge.

Prevention and control methods:

1. Crop rotation. It is best to rotate with crops other than melons, especially flood and drought rotation. Proper use of chicken dung and cow dung.

two。 Use microbial agents to improve the soil. Microbial agents or soil modifiers can be used to reduce salt and alkali to promote the rooting of watermelon, which has a better effect on preventing the yellow leaves of watermelon caused by salt damage.

5. Yellow leaves caused by red spiders

The adults and larvae of red spiders will concentrate on the back of young leaves to suck leaf sap, especially the undeveloped buds, young leaves and flower buds are the main damage parts, so that watermelon leaves can not grow normally. The leaves sucked by red spiders lose their greenness and turn yellow, which can dry up when they are serious.

Control method: root out the weeds around the watermelon field (shed) and cut off the insect source. The red spider has a short life cycle and strong fecundity, so attention should be paid to early prevention and control. 1.8% Chongmike Xing water agent 2000-3000 times or 2% avermectin 1500-2000 times can be used for foliar spray control.

The above is the introduction of the yellowing leaves of watermelon after transplanting. I hope it will be helpful to everyone.