Bacterial shot-hole of cherry laurel

Bacterial shot-hole of cherry laurels (Prunus laurocerasus) in the UK is caused by Pseudomonas syringae pv. syringae. These pages provide relevant information on the symptoms, pathogen, biology and control for UK growers.

This information was last updated in 2023.

An important disease of cherry laurel

Cherry laurel (Prunus laurocerasus) is one of the single most important hardy nursery stock species in the UK; large numbers are produced and widely used in landscaping and amenity plantings. Propagation is via cuttings and production is in containers or in the open ground.

In a survey conducted in 1996-97, leaf spot and shot-hole of cherry laurel was the most prevalent bacterial disease noted on nurseries (research project HNS 71). It is one of the major causes of losses in cherry laurels on commercial nurseries and can result in up to 30% of stock becoming unmarketable. Losses have led some growers to reduce or stop production resulting in increases in the level of imported plant material.

The disease has been reported in the UK, Europe and N. America since the early 1980s. It is particularly troublesome on ground cover laurel varieties such as ‘Otto Luyken’ and ‘Zabeliana’, but the disease affects all varieties and the related Portuguese laurel (P. lusitanica).

Key points

• Bacterial leaf spot and shot-hole of cherry laurels is caused by Pseudomonas syringae syringae in the UK.
• Brown spots 2-10 mm in diameter that drop out to leave shot-holes.
• The primary source of inoculum is the stock plants.
• The pathogen is disseminated with cuttings, plug-plants, liners.
• Local plant-to-plant spread is mainly via water-splash from rain or irrigation.

Recommendations for growers

Growers should:

• Press suppliers for assurances of the health status of young plants.
• Quarantine and carefully check bought-in plants for the presence of symptoms, on arrival and for the next few weeks; reject the entire batch if there are symptoms on any plants.
• Get the identity of the pathogen checked in new outbreaks, especially on imported plant material.
• Keep batches of plants from different sources separate if practical.
• Dispose of visibly infected plants and plant debris quickly
• Clean and disinfect production beds between crops.
• Consider growing cherry laurels under protection.
• Use sub or drip-irrigation or minimise overhead watering.
• Use as wide a plant spacing as economically possible.
• Create barriers of non-hosts plant species between batches of plants.
• Minimise the movement of machinery and people within and between batches of laurels, especially when plants are wet.
• Wash hands when moving between susceptible crops.
• Clean and disinfect pruning and cutting tools frequently.
• Do not mix batches of over-wintered and current season's production on the same beds.
• Carry out trimming and pruning during dry weather and when it is forecast to remain so for a few days after the operation.

Recommendations for propagators

• Keep stock plants separate from production.
• Grow mother-plants under protection with sub-irrigation.
• Consider micropropagation for production of high-health stock plants.
• Test parental material for the presence of Pss; discard any that are positive.
• Only propagate from plants which are known to be free from Pss
• Do not propagate from parental material where any have visible symptoms.
• Clean and disinfect hands, secateurs/knives, trays, benches between different stock plants and batches.
• Do not mix material from different sources.

Symptoms and biology

Find out more about the symptoms of this disease and how to identify it, as well as its epidemiology.

Prevention and control

Bacterial diseases are very difficult to control once disease has become established in a crop and symptoms are widespread. The best means of control is prevention through the use of clean (pathogen-free) propagation/planting material and good nursery hygiene.