Unsightly blemishes on the fruit and leaves of lemon trees characterize Canker disease. However, it is essential to correctly identify the disease as it can be mistaken for other problems. If left untreated, citrus canker can severely damage or 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. If you grow citrus trees professionally or for personal use in your backyard, knowing how to treat citrus canker is important to keep them healthy.

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Overview of Canker:

Citrus canker is a bacterial disease affecting citrus trees, causing unsightly blemishes on the fruit and leaves, leading to premature fruit and leaf drop. While the condition is not harmful to humans, it can significantly impact the vitality of citrus trees. As a result, infected fruit may be safe to eat but needs to be more unsightly to be sold.

Citrus canker is believed to have originated in Southeast Asia and is highly persistent once it becomes established in an area. In an attempt to eradicate the disease, entire citrus groves have been destroyed. It is crucial to detect and treat the disease early to stop it from spreading.

The disease is not limited to Southeast Asia, as countries such as Brazil and the United States also suffer from canker outbreaks. It is essential to have a complete strategy for controlling and managing the disease, which involves detecting it early, providing treatment, and implementing preventative measures.

What Are Citrus Canker Disease Symptoms?

Affected lemon fruit

Canker on lemon fruit

Affected Lemon leaf

1. 1. 1. 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.
      2.  Within days of infection, the affected area becomes raised and exposed as white blisters.
      3. The surface of the blister is sometimes smooth and, in most cases, ruptures.
      4. 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.
      5. 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.
      6. Young branches are also affected by this disease and become very unsightly.
      7. Canker spots can also occur on the fruit. The yellow band always present on the four sides of the leaf spot is not particularly noticeable on the fruit spot. You can 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? 

The attack of Xanthomonas citri causes this disease. The bacteria colonize the abandoned parts of the diseased plant and invade the plant anew. Wind and water spread bacteria 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 with high rainfall and mean temperatures, such as Florida. It’s common to see canker rapidly emerging during fall, slowly during winter, and most quickly 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 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 5:5:50. A little more lime in Bordomixture is better.

Conclusion

Cankers can significantly impact 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 can be a big concern for citrus growers. In order to address citrus canker, it’s crucial to understand how to detect, treat, and prevent it. This will assist you in dealing with the problem effectively.

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I am Gaushoul Agam,

𝐂𝐨-𝐅𝐨𝐮𝐧𝐝𝐞𝐫 & 𝐂𝐄𝐎,
ToAgriculture

As an experienced SA Horticulture Officer in the Horticulture Wing of the Department of Agricultural Extension, Ministry of Agriculture, Government of the People’s Republic of Bangladesh, I am dedicated to advancing agriculture and farming.

With a mission to address global food safety challenges amid a growing population, diminishing arable land, and the impacts of climate change on agriculture, I founded ToAgriculture. Through this platform, I empower readers with modern agricultural techniques, effective pest and disease control, and sustainable agricultural management, leading to a more secure and prosperous future in agriculture.

With over four years of expertise in field crops and seven years in horticulture crops, my knowledge spans fruit and vegetable farming techniques, adept pest-disease management, proficient irrigation strategies, and the art of grafting. Join me on this journey of discovery as I share insights and experiences to guide readers toward a sustainable future.