Erwinia pyrifoliae: the cause of a new bacterial disease on strawberry

What is Erwinia pyrifoliae?

Erwinia pyrifoliae is a bacterial pathogen related to fireblight (Erwinia amylovora), a common bacterial disease of apple and pear in the UK. It was found in the Netherlands in 2013, infecting glasshouse crops of Elsanta in several locations. Other infected cultivars included Selva, Clery, Malling Opal and Ischia. The disease is also thought to have occurred on a commercial production site in Belgium in 2011.The high planting density and typical warm and humid conditions commonly found in UK protected strawberry crops, can increase the risk of bacterial disease occurring. As a high proportion of strawberry plants used in the UK are sourced from the Netherlands, it is likely that the pathogen is already present in the UK, although there have been no reports of related symptoms so far.

What are the symptoms of the disease?

Symptoms include a blackening of the immature fruits, the fruit calyx and attached stems, but no symptoms on the leaves. Blackening is also obvious inside young fruits. Release of bacterial ooze is sometimes observed on the surface of the young fruits and their attached stems. In many cases fruits are malformed.

What can growers do about it?

• Surveillance for the disease by growers and agronomists is important and any suspicious symptoms should be sent for analysis to a plant clinic.
• Erwinia pyrifoliae is not a notifiable or quarantine disease, so no mandatory screening or containment measures are required.
• No plant protection products are registered on strawberry for control of the pathogen and none have been tested for their efficacy against it.
• Based on fireblight data ( amylovora), it is believed that a number of biological products could provide some protection by competing with the pathogen when it is growing on the stigma in flowers. Examples include Aureobasidium pullulans (Boni Protect approved on apples and pears), Bacillus subtilis (Serenade ASO approved on soft fruit and tree fruit, Solani approved on strawberry), Bacillus pumilus (Sonata approved on soft fruit) and Bacillus amyloliquefaciens (Sentinel and Amylo X approved on soft fruit and Taegro approved on strawberry).

Further reading