Lettuce chlorosis virus

Lettuce chlorosis virus (LCV) is a significant plant pathogen belonging to the genus Crinivirus within the Closteroviridae family. It is a single-stranded RNA virus that specifically infects the phloem of host plants. Due to its systemic nature, it causes severe metabolic disturbances that negatively affect plant growth and development.

The virus primarily affects lettuce (Lactuca sativa) and sugar beet, but it also has a wide range of alternative hosts, including many common agricultural weeds. Symptoms usually appear as interveinal chlorosis on older and middle leaves, which later may show interveinal reddening or yellowing. Infected plants exhibit stunted growth, reduced leaf size, and lower biomass, rendering the crop unmarketable.

The biology of the virus is strictly linked to its vector, the whitefly Bemisia tabaci. The virus is transmitted in a semi-persistent, non-circulative manner. The whitefly acquires the virus after feeding on an infected plant and can transmit it to a healthy plant within a few hours. The virus does not replicate within the insect, but remains attached to its stylet for a short duration.

Environmental conditions play a crucial role in disease dissemination. Warm temperatures and high humidity in greenhouses provide ideal conditions for the rapid multiplication of whitefly populations. When high vector pressure coincides with the presence of inoculum sources (weeds or infected crops), the virus can spread throughout the field or greenhouse in a very short time.

Integrated Pest Management (IPM) is the most effective approach for controlling LCV. Key management strategies include:

• Rigorous monitoring and suppression of whitefly populations using sticky traps and selective insecticides.
• Removing weed reservoirs around the greenhouse or field to eliminate virus sources.
• Using screen-protected greenhouses to prevent insect entry.
• Implementing strict sanitation practices to remove crop residues.
• Selecting resistant or tolerant varieties if available for the target crop.