Introduction to Citrus Planting Times and Spring Pest and Disease Control Techniques

When it comes to citrus, I believe everyone is familiar with it. It is a fruit loved by many people, with a great many varieties, including Shatang mandarin, ponkan, Wogan mandarin, green mandarin, Ugly mandarin, and so on. Citrus is cultivated throughout China, especially in the southern regions. Let's take a look below at the Introduction to Citrus Planting Times and Spring Pest and Disease Control Techniques.

I. Citrus Planting Times

1. Spring planting: Spring planting is best carried out in February to March, around the time the spring shoots begin to sprout. During spring planting, temperatures rise and the rainy season arrives, so the survival rate of citrus planted at this time is generally relatively high. However, because the roots have not yet taken hold while the branches and leaves resume growth, the tree vigor is inevitably weakened and the annual growth increment is relatively small, so its growth condition is not as good as that of autumn-planted seedlings.

2. Autumn planting: After the autumn shoots stop growing, temperatures drop while the soil temperature remains relatively high. The citrus branches and leaves no longer grow, but the roots undergo another period of growth. Therefore, planting at this time can reduce the large water demand of branch and leaf growth, the tree consumes less water, and after planting the roots can continue to grow and promptly restore their water-supply capacity, making this a relatively ideal planting time. However, in places threatened by low-temperature freezing in winter, autumn planting is not suitable, and spring planting should be adopted instead.

II. Introduction to Spring Pest and Disease Control Techniques for Citrus

1. Scab

Occurrence pattern: In spring, when there is abundant rain and the temperature reaches above 15°C, the overwintering pathogen produces conidia that invade new tissues. After moderate rainfall and rising temperatures, scab can spread and proliferate rapidly.

Control method: Seize two key periods to spray for protection of citrus new shoots and young fruit. First, when the spring buds begin to sprout and the buds have grown to the size of a grain of rice, spray the first application; second, when two-thirds of the flowers have fallen, apply the second application. If rainy weather occurs and the application is ineffective, spray once more during the young fruit stage in early May.

Fungicide options: difenoconazole, tebuconazole + mancozeb, etc.

2. Anthracnose

Occurrence pattern: It generally occurs comprehensively from April to June each year. After onset, it causes leaf drop, flower drop, and fruit drop, and branches and shoots die. Especially when there is more continuous overcast and rainy weather in spring, this is a favorable period for the spread of conidia, and large areas of orange orchards suffer damage.

This disease also has the characteristic of latent infection. One month after the spring shoots sprout, the branches and leaves begin to carry latent pathogens. By late autumn, most of the new shoots and leaves that emerged that year carry latent pathogens, and the following year, when conditions are suitable, the disease can be triggered.

Control method: Spray during the young shoot stage for protection and also to prevent scab. Focus on the young fruit stage, spraying once about every 15 days, for 3 to 4 consecutive applications. When spraying, be sure to apply thoroughly and evenly, especially fully spraying the fruit stalk, fruiting branches, and fruiting mother branches, with the standard being that the branches and leaves are wet but not dripping.

Fungicide options: difenoconazole, prochloraz, propineb, etc.

3. Citrus canker

Occurrence pattern: The optimum temperature is 25 to 30°C, and the peak onset period in spring is from late April to early May. Young trees and young-age trees are more susceptible. When there is high temperature and abundant rain, and pests such as the citrus leafminer occur in large numbers, canker is severe.

Control method: Emphasize prevention, spray frequently, do a good job of removing and controlling shoots, and release shoots uniformly. For fruiting trees, spray once each at 10 days, 30 days, and 50 days after flower drop; for young trees and nursery stock, spray once each 20 to 30 days after each flush of shoots sprouts. Spray phosphorus and potassium source stock to promote the maturation of new shoots and reduce the damage cycle of the citrus leafminer.

Fungicide options: copper-based formulations, zinc thiazole, mancozeb, pyraclostrobin, etc. Note to rotate and use in combination. But avoid copper-based formulation + copper-based formulation, to prevent the occurrence of compounded phytotoxicity.