Citrus leprosis

Citrus leprosis is a serious viral disease caused by viruses of the Cytorhabdovirus and Cilevirus genera (CiLV). It is considered a significant threat to citrus production globally. The disease is classified as a quarantine pest in many citrus-growing countries because it can drastically reduce fruit yield and lead to the decline of trees if left unmanaged.

The disease is transmitted exclusively by flat mites of the genus Brevipalpus, notably Brevipalpus yothersi. The virus is acquired by the mite during feeding and then transmitted to healthy host tissues. Mechanical transmission or seed transmission does not occur, which makes the management of mite populations the primary strategy for preventing the spread of the virus within and between orchards.

Symptoms of citrus leprosis appear as localized lesions on leaves, stems, and fruits. Initially, these may look like chlorotic spots, which eventually develop necrotic centers. On fruits, these lesions can cause blemishes that significantly decrease market value. In advanced stages, severe leaf drop, twig dieback, and general tree weakening are commonly observed, leading to premature fruit drop.

Environmental conditions that favor the proliferation of Brevipalpus mites are critical for disease outbreaks. The mites thrive in warm, moderately humid environments. In commercial orchards, poor canopy management and lack of airflow within the trees create ideal conditions for the mites to colonize, thereby increasing the risk of virus transmission.

Management and prevention focus on an integrated pest management (IPM) approach. This involves regular scouting for mite presence and the application of chemical acaricides to keep populations below economic thresholds. Strict quarantine protocols for nursery stock movement are essential to prevent introducing the virus into disease-free regions. Additionally, removing heavily infected branches can help lower the viral inoculum in the orchard.