Tristeza disease complex
Tristeza virus
What is Tristeza disease complex (Citrus tristeza virus)?
Citrus tristeza virus (CTV) is present in citrus-producing regions worldwide. It causes multiple diseases in citrus plants, known by different names globally, such as Tristeza, grapefruit stem pitting, lime dieback & yellow dwarf. Symptoms include seedling yellows, stem pitting, and quick decline. Furthermore, Leaves show vein clearing, cupping, and chlorotic flecking. CTV disrupts phloem cells, causing nutrient and water flow issues, leading to fruit withering and tree collapse. Trifoliate orange and mandarin varieties are more tolerant.
How does the Tristeza disease complex (Citrus tristeza virus) occur?
(CTV) reproduces and spreads primarily through grafting and aphid transmission. Grafting infected budwood onto healthy citrus trees can introduce the virus into new plants. When aphids feed on infected citrus trees, they can acquire the virus and transmit it to healthy trees as they move between plants, acting as vectors. The aphids inject the virus into the phloem cells of the tree while feeding, allowing the virus to spread systemically throughout the plant.
Symptoms
1 - Impact on Plants
• Plants: CTV causes reduced vigor, poor fruit quality, yield reduction, and tree decline, leading to tree mortality.
2 - Impact on Soil and Environment
• CTV disrupts nutrient cycling and influences soil microbial communities. • Environment: CTV impacts biodiversity, and pest management practices, and has significant economic implications for the citrus industry. • The virus affects both commercial and residential citrus trees, posing an economic threat.
Solutions
1 - Prevention
1. Obtain budwood from certified nurseries to ensure it is free from CTV and other diseases. 2. Implement effective aphid management strategies, such as using insecticides, employing reflective mulches, or introducing beneficial insects to control aphid populations. 3. Remove and destroy infected plant material to prevent the spread of CTV. Prune infected branches and sterilize pruning tools between cuts. 4. Implement strict quarantine measures to prevent the introduction of CTV-infected plants into citrus-growing areas.
2 - Treatment
1. Remove and destroy severely infected trees to prevent further spread of the virus. 2. Budwood therapy involves heat treatment or shoot tip grafting of CTV-infected plants to obtain virus-free plant material for propagation. 3. Scion-Indexing: Conduct regular indexing of scions for CTV to detect and remove infected trees before they spread the virus to healthy trees.
