Peach yellows

The primary vector for the transmission of this phytoplasma is the plum leafhopper, Macropsis trimaculata. When the insect feeds on the sap of an infected tree, it acquires the pathogen and subsequently transmits it to healthy trees during feeding.

The disease is considered a major phytosanitary risk. Since phytoplasmas cannot be eliminated from woody plants once systemic infection occurs, strict regulatory measures are in place in many regions to prevent its spread.

The disease affects various species of the genus Prunus, with peaches, nectarines, apricots, and almonds being the most susceptible. Plums can also be infected and often act as symptomless reservoirs.

Infected orchards experience significant economic losses. The fruit becomes unmarketable due to premature ripening and poor quality, and the productive life of the orchard is drastically reduced, eventually requiring complete removal of the affected trees.

Symptoms typically become visible during the active growing season, peaking in mid-summer. However, because the pathogen is systemic, it remains present in the tree throughout the entire year.

Transmission by the leafhopper vector is most frequent from late spring to early autumn, coinciding with the peak activity and population density of the insect species responsible for spreading the disease.

Affected trees often show premature leaf yellowing or reddening. The leaves may roll or curl, and their color often turns to a distinct bronzed or golden hue as the season progresses.

A classic diagnostic feature is the proliferation of thin, weak, vertical shoots from the dormant buds, often referred to as "witches' brooms." These shoots have small, pale, and stunted leaves.

Fruit symptoms include premature ripening, poor flavor, and lack of texture. The fruit may also exhibit abnormal coloring patterns. Over time, the canopy thins, growth stops, and the entire tree eventually dies.

The most effective management strategy is the immediate removal and destruction of infected trees. It is critical to dig out the roots to ensure no remaining tissue can harbor the phytoplasma.

Implementing a rigorous vector control program using appropriate systemic insecticides is essential to reduce the population of leafhoppers and prevent the secondary spread of the infection in the orchard.

Growers should prioritize the use of certified, disease-free nursery stock. Avoid propagating material from trees of unknown health status or areas where the disease is known to be present.