The spread of the deadly olive tree disease and potential repercussions

On a global scale, one of the most dangerous plant bacterium is the Xylella fastidiosa, a plant pathogen which causes huge negative impacts not only on the environment but also the economic and social facets.
The bacterium inhabits plant xylem tissue and is spread by insects (cicadas, froghoppers and spittlebugs) feeding from the sap. The xylem is the tissue mechanism that allows the transport of water and nutrients from roots to stems. Once the xylem is compromised, the tree’s ability to move water and nutrients is limited. Disease symptoms include leaf scorching, foliage wilting, dwarfing and even plant death. Currently, there is no available method to cure a diseased plant in the field.
Although the bacterium has been detected on more than 300 plant species, not all of them are affected by Xylella fastidiosa. Amongst the identified host species which are affected are several trees of high economic value, including the olive, stone fruit, vine and citrus.
Xylella fastidiosa has become closely associated with the olives after a strain of the bacterium was first detected in olive trees in Puglia, Southern Italy in October 2013. The common froghopper/ meadow spittlebug (Pulċinell, Philaenus spumarius) has been identified as the vector of the Xylella in Italy, the agent which transmits the pathogen. The disease has also been recorded in Southern France, Spain and Portugal. The devastating consequences of the spread of the disease in Italy resulted in an estimated 60% decline in olive crop yield since 2013 and the death of over a million trees. In 2015 alone, the outbreak caused a 20% increase in olive oil prices. Apart from the economic losses, there are also potentially touristic and cultural losses.
Considering the climatic controls on species distribution, through computer simulations, it was found that the areas which are most at risk to certain subspecies of the Xylella fastidiosa are located in southern Europe.
EU financial support has become available to compensate owners for the value of their destroyed plants and to enact projects to restore olive oil production. The institutional delay in intervention against the Xylella fastidiosa in Italy, now exacerbated by the national effort to contain the spread of Covid-19 can potentially hinder the timing and efficiency of the response against the plant pathogen. Possibly, a secondary negative longer-term impact would be further spread of the bacteria. Although it is recognised that main EU funding is being diverted to tackle the immediate and necessary health threat caused by the coronavirus, adequate food supply and security through EU funding on agriculture are still important and needed.
Long-distance spread of the bacterium is caused by the movement of infected propagating material (e.g. budwood, rootstock seedlings and budded trees) through harbours and airports. Given that Malta is an island, and the fact that the infection spreads via the movement of infected propagating material, it is only human intervention which can either spread the disease through shipping or prevent it from arriving.