Fire blight is considered to be one of the world's most harmful diseases in apple and pear trees. In the summer of 2020, the disease was detected in a commercial orchard in Norway.
In many countries, attacks of fire blight have major economic significance in terms of fruit production, and the disease is also known to destroy ornamental plants and trees in parks and green spaces.
Fire blight was first detected in Norway 33 years ago, but a variety of measures kept it away from fruit production areas. Sporadic outbreaks of the disease have occurred in apple trees in private gardens, but now the bacterium has been detected for the first time in commercial fruit production in Norway.
"Suspected fire blight was confirmed in all the samples, first through a lateral flow test and then a DNA analysis," explains NIBIO researcher Juliana Perminow.
Fire blight can spread very quickly at temperatures above 20°C. Weather conditions, including high temperature, moisture and wind were favourable to the development and spread of fire blight in Ryfylke district in 2020, when outbreaks were observed in July in Cotoneaster in several locations.
Latent infection of fire blight in plant material generally represents a major risk of the harmful bacterium introduced from abroad. Until November 2015, the import of fire blight host plants to Norway was prohibited, but the authorities have since allowed the import of plants for planting of pome fruit from countries known to have a prevalence of fire blight.
Fire blight is very difficult to control, since there are no chemical products that work against the bacterium. Intensive work has been ongoing since 1986 to identify and destroy infected plants. However, for the last few years there have been inadequate resources to remove all of these in cities like Bergen and Stavanger. Instead, the focus has been on the preventive removal of healthy host plants close to areas of fruit production and nurseries.