New leaves are slender and small, which is related to more nitrogen on the one hand and zinc deficiency on the other. Nitrogen is used to elongate cells, but the leaves are crisp and thin. In fertilization management, a large number of large chemical fertilizers are used, and base fertilizer and topdressing are used. It is necessary to control the use of nitrogen. In the germination stage of spring shoots, whether the spring shoots are normal or not directly determines the trend of trees throughout the year.

1, old curved leaf

The main causes of old leaves curling are: fertilization, root injury, boron deficiency and nematode damage.

2. Curl of new leaves

Curl of new leaves can be subdivided into reverse curl of new leaves and non-extension of new leaves.

The new leaves are mainly caused by low temperature stress such as insufficient nutrient supply during the growth period of spring shoots, cold in late spring or the ingestion of aphids. On sugar oranges, yellow vein disease can also lead to the lodging of new buds.

Pesticide damage or insect pests can also cause new leaves not to stretch, such as propargite, gibberellin, 2,4-D phytotoxicity, thrips and so on.

What preventive measures are there?

1, strengthen nutrition management and restore trees.

When supplementing nutrition, both leaves and roots should be supplemented. Biological stimulators such as alginic acid can be applied to roots, and brassinolide containing boron and zinc and foliar fertilizer can be sprayed on leaves to restore tree vigor.

2. Raise roots, promote roots and strengthen roots

Apply strong root fertilizer before new buds germinate, spray roots with humic acid and seaweed to supplement root nutrition and improve soil aggregate structure.

3, cold and antifreeze

Pay attention to the weather forecast every day to prevent bad weather such as late spring cold, and spray functional foliar fertilizer such as humic acid before late spring cold to improve the stress resistance of young citrus trees.

4. Prevention and control of pests and diseases

Bacteria and pests are active in spring, so predatory mites can be used to control red spiders, thrips can be trapped with blue boards, aphids can be trapped with yellow boards or drug control can be carried out.

Recommended drugs: (Red Spider) 22% avermectin spirodiclofen suspension 4000-5000 times; (Aphids) 30% Pyrethroid Chlorpyrifos EW 1000- 1500 times.

Early prevention is very important for root-knot nematodes. Before transplanting seedlings, soak the roots in hot water at 48℃ 15 minutes, or soak the roots in 3% avermectin thiamethoxam emulsion 1000 times.

Root-knot nematodes can also be biologically controlled by Verticillium crassum, Paecilomyces lilacinus and Bacillus subtilis. When in use, a hole is opened around the root, Verticillium dahliae is applied, and the soil is covered for 2 cm. Or spray 10% thiamethoxam granules 15 ~ 20g on each plant, and then cover the soil for irrigation.