Unsightly blemishes on the fruit and leaves of lemon trees characterize Canker disease. However, it is important to properly identify the disease as it can be mistaken for other problems. If left untreated, citrus canker can severely damage or even kill the tree. As a citrus farmer, this is a problem that you may face. In this blog post, we will discuss the causes of canker and the most effective methods for treating and preventing it. Whether you’re a professional grower or a backyard gardener, understanding how to treat citrus canker is crucial for maintaining healthy citrus trees.
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Overview of Canker:
Citrus canker is a bacterial disease that affects citrus trees, causing unsightly blemishes on the fruit and leaves, which can lead to premature fruit and leaf drop. While the disease is not harmful to humans, it can have a significant impact on the vitality of citrus trees. As a result, infected fruit may be safe to eat but is often too unsightly to be sold.
Citrus canker is believed to have originated in Southeast Asia and is extremely persistent once it becomes established in an area. In an attempt to eradicate the disease, entire citrus groves have been destroyed. This highlights the importance of early detection and treatment to prevent the spread of the disease.
The disease is not limited to Southeast Asia, as countries such as Brazil and the United States also suffer from canker outbreaks. This highlights the need for a comprehensive approach to controlling and managing the disease, including early detection, treatment, and prevention measures.
What Are Citrus Canker Disease Symptoms?
- Growing young leaf first develops light yellow spots. In the initial stage, the spots are about the size of Alpin’s head. This spot can occur on both sides of the leaf. However, in most cases, the spots are more on the reverse side of the leaf.
- Within a few days of infection, the affected area becomes raised and exposed as white blisters.
- The surface of the blister is sometimes smooth and in most cases ruptures.
- As the disease progresses, the color of the fibers of the affected part first turns white and later turns brown. The center of the scar looks like a volcanic crater. Gradually the spots increase in number and size and spread over most of the leaf. Eventually, the tissue within the scar dies, and sometimes this dead area dries up and sloughs off. Because of this, there are small holes in the leaf.
- Within three weeks, the diameter of the spots on a growing leaf may reach 3 to 4 millimeters. In most cases, the typical spots are surrounded by yellowish fibers.
- Young branches are also affected by this disease and become very unsightly.
- Canker spots can also occur on the fruit. The yellow band that is always present on the four sides of the leaf spot is not particularly noticeable on the fruit spot. You can clearly see the cavity of the canker on the fruit. The disease only affects the lemon peel and does not cause significant damage to the juicy interior.
What Causes Citrus Canker?
This disease is caused by the attack of bacteria called Xanthomonas citri. The bacteria colonize the abandoned parts of the diseased plant and invade the plant anew. Wind and water spread bacteria present in infected plants to different plants in the field. Wind-driven rain plays a significant role in the spread of X. axonopodis, the bacteria that causes citrus canker. Splashed rain and wind easily disperse the bacteria, however, their quantity decreases after the first event of wind-blown rain. Additionally, the bacteria thrive in warm weather. This is why c. canker is more prevalent in areas that receive high rainfall and have high mean temperatures, such as Florida. It’s common to see cankers rapidly emerging during fall, slowly during winter, and most rapidly in mid to late spring.
How To Treat Citrus Canker Disease?
Collect disease-free seedlings from disease-free areas to plant as seedlings. Thoroughly check imported trees for the disease before planting them in orchards.
- In orchards where the canker disease first appears or is newly detected and has not spread yet, remove infected trees by burning them.
- Disinfect clothing and equipment before entering the garden to prevent the spread of the disease.
- In areas where the disease is widespread and removing the trees is not a viable option, implement measures to reduce the incidence of the disease.
- During dry weather in the winter, the disease’s spores are less active. Keep the trees healthy by providing moderate fertilizer and irrigation during this time. Prune affected parts of the tree and spray with copper oxychloride at a 2% concentration. Use insecticides separately from the copper oxychloride spray.
After 2-3 months of fruiting, spray the Bordeaux mixture at a ratio of 5:5:50. A little more lime in Bordomixture is better.
Cankers can have a significant impact on the vitality of citrus trees, causing unsightly blemishes on fruit and leaves and leading to premature fruit and leaf drop. The disease is not harmful to humans, but it can be a big concern for citrus growers. To combat this issue, it is important to know how you treat citrus canker by taking the necessary steps to detect, treat, and prevent it.