Exocortis
Citrus exocortis viroid (CEVd)
What is Exocortis Citrus exocortis viroid (CEVd)?
Citrus exocortis viroid (CEVd) is a small RNA molecule that infects citrus plants, specifically those belonging to the Pospiviroidae family and Pelamoviroid genus. Its infection leads to a severe viroid disease known as citrus exocortis, or scalybutt, which has a significant impact on citrus crops globally. CEVd primarily affects citrus rootstocks such as trifoliated orange, Rangpur lime, and Swingle citrumelo, which are highly susceptible to the disease. Infected trees display distinct symptoms including stunted growth, leaf yellowing (chlorosis), and the development of a rough, corky bark on trunks and branches.
How does Exocortis Citrus exocortis viroid (CEVd) occur?
CEVd, or Citrus Exocortis Viroid, is primarily transmitted through vegetative propagation methods like grafting and budding, where an infected citrus portion or bud is introduced to a healthy rootstock or tree, leading to viroid spread. Additionally, CEVd can be transmitted through contaminated tools used in citrus cultivation. Unlike some other plant pathogens, CEVd is not known to have natural insect vectors involved in its transmission process.
Symptoms
1 - Plant Health
This disease has detrimental effects on fruit yield and quality, posing a significant threat to citrus production. If left unchecked, it can ultimately result in the decline or death of affected trees, further compounding the economic and agricultural impact of citrus exocortis.
2 - Biodiversity and Ecological Balance
• CEVd primarily affects cultivated citrus plants and does not directly impact wild citrus or other plant species. • The presence of CEVd in citrus orchards can disrupt ecological balance. • Loss of citrus trees may impact habitat and food availability for beneficial insects and birds.
Solutions
1 - Cultural Practices
1. Obtain propagation material from reliable and certified sources to ensure it is free from CEVd and other viroids. 2. Implement strict sanitation measures to minimize the spread of CEVd. 3. Promptly identify and remove trees showing symptoms of CEVd infection. 4. Select rootstocks that exhibit resistance or tolerance to CEVd. 5. Conduct regular monitoring and testing of citrus plants for the presence of CEVd. 6. Implement good agricultural practices and integrated pest management strategies to maintain healthy citrus trees.
2 - Chemical Control
Currently, there are no specific chemical treatments available for the direct control or eradication of Citrus exocortis viroid (CEVd) in infected citrus trees. Management of CEVd primarily relies on preventive measures and cultural practices.
