Detailed Explanation of Key Technical Points for Citrus Pest and Disease Control
Citrus trees are one of the common tree species in orchards, generally bearing golden-yellow fruit that hangs all over the branches in autumn and winter. Citrus tastes sweet and sour and is rich in vitamin C, making it very popular in the market. During the specific cultivation of citrus, some diseases often appear. Today let us take a look at the key points of citrus pest and disease control technology.
1. Scab
Occurrence pattern: In spring when there is abundant rain and the temperature reaches above 15°C, overwintering pathogens produce conidia and invade new tissues. After moderate rainfall and rising temperatures, scab can spread and proliferate rapidly.
Control method: Grasp two key periods for spraying to protect new citrus shoots and young fruit. First, when spring buds begin to sprout and the buds are the size of a grain of rice, spray the first application; second, when two-thirds of the flowers have fallen, apply the second spray. If cloudy and rainy weather occurs and the spraying effect is poor, 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 dieback of branches and shoots. Especially when there is more continuous rainy weather in spring, this is a favorable period for conidia transmission, and large areas of citrus orchards suffer damage.
This disease also has the characteristic of latent infection. One month after spring shoots sprout, the branches and leaves begin to carry latent pathogens. By late autumn, most of the newly produced shoots and leaves of the year carry latent pathogens, and in the following year, when conditions are suitable, the disease can be triggered.
Control method: Spray during the tender shoot stage for protection and also to prevent scab. Focus on the young fruit stage, spraying once about every 15 days for 3~4 consecutive times. When spraying, be sure to apply thoroughly and evenly, especially fully covering the fruit stalk, fruiting branches and fruiting mother branches, with the standard being that branches and leaves are wet but not dripping.
Fungicide options: difenoconazole, prochloraz, propineb, etc.
3. Brown spot
Occurrence pattern: It generally begins to occur in late March, with the peak period in late spring and early summer. The optimum temperature is 22~28°C. It occurs severely in orchards with poor drainage, weak tree vigor and more wounds on the tree body.
Control method: Prune appropriately, manage water and fertilizer reasonably, and spray fungicides in time for protection. Spray at intervals of about 10 days when spring shoots are 3~5cm, at the flower-falling stage, at the young fruit stage and before and after rainy days.
Fungicide options: propineb, pyraclostrobin, etc. Pay attention to using systemic therapeutic agents, especially after disease onset.
4. Citrus canker
Occurrence pattern: The optimum temperature is 25~30°C. The peak onset period in spring is from late April to early May. Young trees and young-aged trees are more susceptible. When there is high temperature and abundant rain and pests such as citrus leafminer occur in large numbers, citrus 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 20~30 days after each flush of shoots sprouts. Spray phosphorus and potassium source reservoir to promote maturation of new shoots and reduce the damage cycle of citrus leafminer.
Fungicide options: copper-based formulations, zinc thiazole, mancozeb, pyraclostrobin, etc. Note to rotate and compound them for use. However, avoid copper formulation + copper formulation to prevent the occurrence of compounded phytotoxicity.