Plum pox

Plum pox, also widely known as Sharka disease, is caused by the Plum pox virus (PPV), a member of the Potyvirus genus. It is arguably the most destructive viral disease affecting stone fruit trees worldwide, leading to significant economic losses in fruit production.

The virus primarily affects species within the Prunus genus. This includes plums, apricots, peaches, nectarines, and almonds. The infection is systemic, meaning the virus spreads throughout the entire tree, eventually affecting the leaves, flowers, and fruit, rendering the harvest unmarketable and of poor quality.

Symptoms are often diagnostic and can be seen on leaves as chlorotic spots, rings, or line patterns. On the fruit, the virus causes irregular depressions, dimpling, and color changes. A distinct symptom is often found on the stones (pits) of affected fruits, where pale rings or mottled patterns appear, which is a hallmark of this specific viral infection.

The virus is mainly transmitted by various species of aphids in a non-persistent manner. However, the most common way it spreads over long distances is through the movement of infected plant material, such as budwood, grafts, and nursery stock. Once a tree is infected, it remains a permanent source of the virus for vectors.

Management of Plum pox is challenging because there is no cure for infected trees. Strategies focus on strict quarantine measures, the use of certified virus-free rootstocks and scion wood, and the removal and destruction of infected trees. Controlling aphid populations can reduce the rate of spread but is rarely sufficient to stop an established outbreak entirely.