During the surveillance programme conducted by the Plant Health Directorate within the Parliamentary Secretariat for Agriculture, Fisheries and Animal Rights with the objective of monitoring the status of pest occurrence, the Directorate found a number of citrus trees infected with the Citrus Tristeza Virus (CTV). The infected trees, originating from Sicily, were discovered in various garden centres following sampling and testing.

On detection of the virus, the Directorate activated the contingency plan and carried out the destruction of the infected consignments. In order to ensure the eradication of this pest, the general public is being asked to notify the Directorate of any purchase of citrus trees which occurred in the last six months.

The Citrus Tristeza Virus is the most destructive citrus disease worldwide. Caused by a Closterovirus, it is mainly transmitted by grafting of infected material and aphid vectors. The symptoms are not always visible and may remain unnoticed for a number of years without affecting fruit setting and production.

The most recent outbreak dates back to 2012 when an area in San Blas and Da?let Qorrot Valleys in Gozo was demarcated. During the emergency action, citrus trees of various species were felled from the contingency area and the pest was completely eradicated. In 2013, the virus was detected again in trees brought from abroad in a local nursery.

Monitoring surveys for both the CTV and its vector has been conducted in different citrus orchards throughout Malta and Gozo since 1999, with around 800 samples collected each year. In 2004, Malta was declared as a protected zone for this disease. As a result, movement of susceptible plants is subject to monitoring, and citrus fruits introduced into Malta have to be free from any foliage and peduncles, which reduces the risk of transporting the disease and its vectors. Any citrus trees for planting have to originate from authorised nurseries and be certified as free from the virus and vectors.

The virus cannot be controlled by any pesticide, and the only control mechanism for this disease is that of uprooting and burning infected trees and applying pesticides for the vectors. Since the symptoms are not always visible in view of latent infections, the public is requested to notify the Directorate of any purchases of citrus trees which occurred in the last six months. Trees originating from the same consignments in which infected trees were detected will be tested for the virus.

Source: Government of Malta