Olive trees face deadly disease – Losses may amount to over €20 billion

Is Olive Quick Decline Syndrome (OQDS) the COVID-19 of olive trees?

Writer: Sophie Maho Chan
Editor: Karolay Lorenty
Artist: Elena Natsumi


As the world combats the COVID-19 pandemic, another species is fighting a losing battle against a deadly disease of its own. Termed Olive Quick Decline Syndrome (OQDS), the disease is killing olive trees across Europe at an unprecedented rate, and according to a model-based study published last month, this may cost Europe over €20 billion. Such findings have caused panic among many — and understandably so, considering the current economic state of Europe. Just in the past month, statistics after statistics have been quoted on The Independent and BBC among other news media.

Behind this disease is a well-known plant pathogen Xylella fastidiosa. Spread by insects known as spittlebugs, the bacteria feed on the xylems (the water vessels) of their hosts. As the bacteria multiply in the xylem, it obstructs the water-nutrient transport and deprives olive trees of their basic needs. Common symptoms of OQDS include ‘leaf abscission, dieback, delayed growth, and death’. Farmers in Italy have described the rapid rate at which infected trees lose their colouration, leaving groves of ‘burnt’ trees and ‘lifeless trunks’ along what used to be iconic, touristic landscapes. Worst of all, there is currently no cure and the disease spreads quickly. Sounds familiar? Maria Saponari, plant virologist at the Institute for Sustainable Plant Protection in Italy, compares OQDS to Covid-19.

What is surprising, however, is not the disease itself. In fact, OQDS was discovered back in 2013 after the deaths of ancient olive trees were observed in Puglia, Italy. Even then, entire groves of over 230,000 hectares were taken down. In the years that followed, the bacteria is known to have killed millions of olive trees in Italy and Spain, both countries which are among the top olive oil producers.

 In 2015, Italy declared a state of emergency over this crisis. However, quarantine efforts, which require uprooting and removal of infected trees as well as their healthy neighbours, have faced strong opposition by environmentalists and farmers alike. Many have even claimed that such containment measures are based on scientific misinformation and refused to cooperate. Politicians were slow to act; amidst protests and court cases, eight mayors in Puglia declared they would not comply with insecticide requirements. This has significantly and continuously delayed the containment of the disease over the last many years, causing it to spread to other regions of Italy as well as across borders to Spain, France and Portugal. Indeed, it is uncanny how many parallels exist between this plant disease and our current COVID-19 pandemic.

So why the sudden spike in media attention? Arguably, this speaks to the economic-oriented mindset we have come to accept. 

In the publicized study, researchers modelled the potential economic impact of OQDS in Italy, Spain and Greece, which account for 95% of global olive oil production. They found that if nothing significant is done to prevent the spread of the pathogen, losses could amount to €5bn (£4.2bn) for Italy, €17bn (£14.5bn) for Spain and €2 (£1.7bn) for Greece over the next 50 years. The good news is that the study also found that if measures were taken to protect olive groves, like entirely replanting the trees with resistant varieties, losses could be reduced to €1.6bn (£1.3bn) in Italy, €5bn (£4.4bn) in Spain and €0.6bn (£0.5bn) in Greece. However, this will not be without consequences; there will be a shortage in supply and spike in olive-product prices.

Yet, this issue must not be reduced to economic losses and consumer needs. To those involved in the agricultural sector, these olive tree orchards hold significant cultural and historical purpose; many were inherited over generations and even survived the war. Thus, replacing trees, especially those that are currently healthy, is not the ideal scenario by any means. Nonetheless, having tried insect-repelling clays and vegetative barriers as well as having conducted genetic analyses to try to understand differential susceptibility, researchers claim that finding a resistant species is the most promising and environmentally sustainable strategy. Most agree with this view and increasing efforts are going into relevant research.

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