Citrus Canker: How To Spot, Prevent And Beat It


Updated: 4 Feb 2024

155


Hello guys, and welcome to the land of plants!

Do you know why citrus canker is the most deadly disease? Don’t worry, in this blog, we will cover every possible point to make your doubts crystal clear.

One of the most destructive citrus diseases is Citrus canker. It affects almost all of the major citrus crops. The bacterium Pseudomonas citri or Xanthomonas citri is the cause of this disease. Lesions consisting of depression with raised margins are called canker.

It’s time to dig in, get your hands dirty, and let the adventure begin!

Which organism causes Citrus Canker?

 Xanthomonas axonopodis pv. citri is an aerobic, rod-shaped bacterium that causes citrus canker. It is a gram-negative bacterium with a thin layer of peptidoglycan. Under favorable conditions, it can cause severe infections such as fruit drop and dieback.

Classification of Citrus Canker

Citrus canker can be classified as:

KingdomMonera
PhylumPseudomonadota
ClassGammaproteobacteria
OrderXanthomonadales
FamilyXanthomonadaceae
GenusXanthomonas
SpecieX.Axonopodis

Hosts

Any organism in which a parasite lives is called a host. The host provides food, shelter, and habitat to the parasite. Here is a list of some of the hosts of citrus canker:

  • Oranges
  • Lime
  • Lemons
  • Grapefruit
  • Tangelo
  • Kumquat
  • Pomelo
  • Calamondin

Citrus Canker’s Symptoms

The symptoms are obvious on newly emerged leaves, twigs, and fruits. Serious infections include fruit drop, shoot dieback, and defoliation. Infected twigs dry up.

Initial stage

 At first, these symptoms present as tiny, slightly raised, round, light green spots. After infection, it took 7 to 14 days to be seen by the naked eye.

Final stage

As the infection progresses, these spots transition to a rupture with a grayish-white color and develop a brown corky texture with sunken centers. Often, the lesions are encircled by a yellow-colored halo.

Size of lesions

The lesions vary in size. They can range from 1 to 9 mm on the leaves in diameter while on the twigs and fruits, they can vary up to 1 cm in diameter or length.

Extreme infections can weaken the tree on the leaves, twigs, and branches. If a fruit may appear deformed and scabbed, it is also severely infected.

Spread

  • Movement and trade of the infected plant materials can spread the disease internationally (long distances).
  • Short-distance dispersal can occur by wind-driven rain, water splashes, and flooding.
  • Infection can be spread easily by contaminated equipment and tools.
  • Insects and birds can transmit the disease from one field to another.
  • It can be moved through the workers’ shoes, hands, and clothing.

Favorable Conditions

  • High temperature 
  • Humid climate
  • High moisture
  • High rainfall
  • Poor sanitation

Disease Cycle

Soil serves as the essential source of infection.  For example, bacterial cells can easily survive in the soil for 4-5 years without requiring the host. The bacteria enter citrus leaves and other plant parts through entry points created by injuries or through natural openings called stomata.

During rainstorms, citrus canker bacteria can be transported between trees, covering distances of up to 100 meters. They grow and multiply in the intercellular spaces and cause the symptoms.

Disease Cycle of Citrus Canker

Prevention and Cure

There is no cure for citrus canker but several measures can be taken to prevent the disease from spreading:

  • Purchase citrus plants from a trusted source
  • Field sanitation
  • Use of canker-free nursery stock
  • Burning all the infected trees
  • Use of copper compounds and antibiotics (streptomycin and agrimycin) 
  • Bordeaux mixture can be used
  • Disease-free planting material

Facts about Citrus Canker

  • Seeds do not transmit citrus canker.
  • Citrus canker is a plant disease that does not harm people or animals.
  • Japan’s 85% of citrus production is moderately resistant because of the Unshui (Satsuma) orange.
  • In some cases, the lesions caused by citrus canker can resemble a smiley face due to their circular shape with a central pore and a surrounding halo.

History

Citrus canker is endemic in Southeast Asia & Japan. From these two regions, the disease disseminated to all of the citrus-producing continents. In 1912, the US, the citrus canker appeared in the state of Florida. The contamination source was the infected nursery stock from Japan. Later from there, it gradually spread to all of the Gulf countries and beyond. It took more than 20 years, during which more than 1/4 of a million fruit trees and over 3 million nursery trees got infected and later died. Millions of dollars in expenses were incurred along with the inconvenience and extra heartache until the citrus canker finally was successfully terminated from Florida, the citrus capital of the US.

Until 1949, an additional 20 years were employed to eliminate citrus canker from the US. In August 1984, a leaf spot bacterial disease that resembled citrus canker popped up in Florida. The disease was initially thought to be a citrus canker. This prompted a novel wave of eradicatory steps, destroying a minimum of 20 million young orchard and nursery trees by 1990. In 1986, however, the Asiatic canker or true citrus canker (canker A) emerged in Florida, leading to active eradication efforts in disease-affected areas until 1992. Florida was free of citrus canker after two years without any disease findings in early 1994, and all of the related regulations got upheld.

Countries producing citrus without the canker disease still strictly prohibit the import of fruit and citrus plants from non-canker-free countries.

Conclusion

In this article, we have explored the symptoms and their stages, classification, spread, favorable conditions, disease cycle, history, and treatment for the disease of citrus. By taking these measures you will be able to prevent the spread of infection. In addition to this, we also have to get to know about some impressive facts about citrus canker.

My recommendations:

  • Spacing between the plants is beneficial for the aeration process as it will enhance the quality of the fruit. It will prevent your fruit from decaying. Spacing must be kept between 4.5×4.5
  • Intercropping can be done that will help our citrus crop to have good quality fruit, increased growth and perform better than before. It can be done with guar and wheat.

Feel free to Contact Us. Just ask your questions, don’t hold them tight, and I’ll shed some light and make it right. 

FAQs about Citrus Canker

We have some frequently asked questions that will help you know more about citrus canker

What is the scientific name of citrus canker?

Pseudomonas citri or Xanthomonas axonopodis pv. Citri

What is citrus?

Citrus is a fruiting plant. It grows best in subtropical regions. It is a high source of vitamin C. It includes:

  1. Orange
  2. Lemon
  3. Lime
  4. Grapefruit
What are the pests of citrus?

Pests are small things or insects that are harmful to the plants. Citrus pests include

  1. Whiteflies
  2. Stem borers
  3. Termites
  4. Mealybugs
  5. Fruit flies
What is citrus canker?

Citrus canker is a bacterial disease that causes lesions on the leaves, stems, and fruits. It is caused by Xanthomonas axonopodis pv. citri. It is one of the most destructive citrus diseases.

What is the mode of transmission for citrus canker?

Citrus canker can be dispersed by various means:

  1. Wind
  2. Rain
  3. Insects
  4. Birds
  5. Contaminated shoes, tools, and clothes of workers

Dr. M Awais

Dr. M Awais

This is Awais. I am a phyto doctor. I have studied plants my whole life. Plants are my best friends. I have gathered detailed information about plants. My brilliant team is always ready to accept the challenges. Together, we find the solutions for our clients.

Please Write Your Comments