While Huanglongbing has taken center stage when it comes to citrus production concerns over the past few years, there is another incurable disease that growers should not overlook—citrus canker.

Citrus canker is a bacterial disease caused by the Xanthomonas citri pathogen and can be detrimental to the health of citrus trees and the marketability of fruit. Upon infection, this disease can result in severe defoliation, premature fruit loss and drastic reduction in quality of citrus crops.

Early symptoms of citrus canker manifest as blister-like lesions on leaves and stems that darken and become scabby as they mature. Dark brown, raised lesions will also appear on fruit, often with a yellow halo surrounding the spot. When left untreated, infected trees can experience defoliation and premature fruit drop.

The highly contagious disease thrives in warm, wet conditions and can spread rapidly from grove to grove in FL’s subtropical climate. The disease spreads via natural causes, such as wind and rain from storms, as well as movement by citrus leafminer, birds and other animals. Man-made causes also contribute to the spread of citrus canker, such as overhead irrigation and human or equipment movement of infected plant matter.

According to UF/IFAS Extension, citrus canker was first detected in FL in 1910. Between then and 1994, the disease was declared eradicated twice, but it was spotted again in Miami in 1995. By 2000, a statewide mandatory eradication plan was in place with quarantines and decontamination procedures. However, the mandatory plan ended in 2006 due to widespread infection of citrus canker. Since eradication of citrus canker is no longer a viable option in FL, management of the disease is more crucial than ever.

We recommend the following management tactics to protect groves from citrus canker and prevent further spread of the disease in FL:

• Decontaminate equipment and personnel upon exiting a grove to reduce chances of human and equipment movement of citrus canker. The Citrus Health Response Program provides guidelines for decontamination products and methods.
• Implement natural or man-made windbreaks in groves. According to UF/IFAS Extension, reducing wind speeds to under 18 MPH significantly diminishes the spread and severity of citrus canker.
• Apply an effective insecticide to reduce citrus leafminer populations that cause wounds to citrus leaves and allow the canker pathogen to easily enter. Minecto® Pro is a broad-spectrum insecticide that controls overlapping pest populations, including citrus leafminer and Asian citrus psyllid.
• Stimulate natural defense in citrus trees with products like Blockade® 50WG plant activator. Similar to a vaccination, Blockade induces PR protein production in both bearing and non-bearing citrus trees to help trees protect themselves from infection.
• If citrus canker is detected, remove the infected trees and surrounding healthy trees to slow the establishment of the disease.

Although there is no cure for citrus canker, growers can protect the health of their citrus trees and marketability of their fruit with a proper canker prevention program. Visit the Syngenta website to learn more about our citrus crop protection products and the ways we support the citrus industry.

Sign up for the Know More, Grow More Digest to receive twice-monthly agronomic e-mail updates pertinent to your area.

All photos are either the property of Syngenta or are used with permission.

Syngenta hereby disclaims liability for third-party websites.