Donato Gerin, Stefania Pollastro, Rita Milvia De Miccolis Angelini, Francesco Faretra, Franco Nigro
Department of Soil, Plant, and Food Sciences - University of Bari Aldo Moro
The prokaryote Candidatus Phytoplasma pruni is the agent responsible for the disease in stone fruit plants known as X-disease, which is causing significant economic losses in the United States and Canada.
This phytoplasma is transmitted by at least eight species of pests to plants of the genus Prunus, but it has a wide range of host species, especially in the Asteraceae and Brassicaceae families. Furthermore, like most phytoplasmas, it can be transmitted through grafting and easily spread through propagation material.
On cherry trees, the fruits appear discolored and distorted, with a bitter or tasteless flavor. Initially, symptoms appear on a single branch or often only on a single cluster of fruits, spreading to the entire tree in subsequent seasons. During the growing season, the leaves show chlorosis, curling, reduced size, and premature shedding (Figure 1), while in later stages, bronzing or anthocyanosis along the central and basal veins is observed. The type and severity of symptoms may vary depending on the cherry variety and the strain of Ca. Phytoplasma pruni.
Figure 1. Symptoms caused by X-disease on sweet cherry (Harper et al., 2023). A, size, color, and shape of infected fruits compared to normally developed fruits; B, reduced-sized leaves with enlarged leaf stipules; C, branch dieback.
Considering the increasing incidence of X-disease observed in recent years in both the United States and Canada, an intervention plan has been published (Harper et al., 2023) with the aim of providing information on the biology of Ca. Phytoplasma pruni, the expression of the disease, host-pathogen and pathogen-vector interactions.
Furthermore, the plan includes strategies to prevent the spread of the pathogen through management programs that, as outlined in suitable phytosanitary regulations for containment, are based on the use of certified propagation material, the removal of infected plants, and the control of weed hosts, as well as vectors.
Download the full document (Harper, et al. (2023). Recovery Plan for X-Disease in Stone Fruit Caused by ‘Candidatus Phytoplasma pruni’. Plant Health Progress, 24(2), 258-295. https://doi.org/10.1094/PHP-02-23-0016-RP
Cover Photo: WSU Tree Fruit
05 Aug 2024
A detailed dashboard captures and uploads information in real time. AgPick promotes traceability by informing growers who has harvested their fruit, who is leading production and what quality problems can be attributed to the pickers.
31 Mar 2026
Chilean cherry imports in Argentina hit 1,273 tons, setting a new record. Amid Chilean oversupply and steady premium demand, the market absorbs higher volumes without price collapse, raising questions about future balance and competition in the sector.
03 Jul 2026
Research in Moldova on sweet cherry shows Thin spindle improves yield, fruit quality and canopy management in high-density orchards on Gisela 6, while Improved thin spindle boosts large premium fruit, uniformity and commercial value for modern intensive cherry production.
03 Jul 2026
Chilean cherries 2025/26 face a more saturated China market, flat FOB prices and rising pressure on quality, timing and destinations. Diversification toward the United States and other markets is becoming crucial to protect Chile’s profitability and fruit exports now.
