Spread of Erwinia amylovora via commercial apple fruit: an insignificant risk
In 1998, the risk of introduction of Erwinia amylovora (causing fireblight - EPPO A2 List) associated with the movement of commercial apple fruits was assessed and was considered insignificant (see EPPO RS 98/084). It can be recalled that EPPO has always taken the view that this risk was negligible, however some countries (e.g. Australia, Japan) have taken the opposite view and prohibit imports of pome fruits from countries where the disease occurs. This potential risk was reassessed based upon data available since 1998. This analysis concluded that the low epiphytic fitness of E. amylovora on apple fruit, the documented low incidence of viable populations on mature apple fruit and the lack of a documented pathway by which susceptible host material could become infected from fruit-borne inoculum remain unchanged. Therefore, current knowledge still supports the view that the spread of fireblight via imports of apple fruit is highly unlikely. The risk of transmitting fireblight (introduction followed by an outbreak) to disease-free areas was estimated by using an already published model under different scenarios (various disease levels in the orchard, presence/absence of phytosanitary measures in the importing countries). According to the different scenarios, the likelihood of inducing an outbreak with imports of infected apples ranged from 1 outbreak in 5 217 years to 1 in 753;144 years. It is concluded that the risk of introducing E. amylovora on commercial apple fruit and establishing new outbreaks of fireblight is so small as to be insignificant.
Sources
Roberts RG, Sawyer AJ (2008) An updated pest risk assessment for spread of Erwinia amylovora and fire blight via commercial apple fruit. Crop Protection 27(3-5), 362-368.