Xylella fastidiosa- the Olive Pest

If you were to fly over southern Italy’s olive groves, you’d see dense lines of trees stretched over the hills, flourishing in the Mediterranean climate. Livelihood, culture, and culinary tradition converge in these groves in a way that is emblematic of Italy itself. But with a closer look and some frank conversations with those who work the groves, you would discover that a struggle is raging in this idyllic setting. A struggle with the pest Xylella fastidiosa.   

What is Xylella? 

Xylella fastidiosa is a bacterium that attacks the nutrient and water transportation system of plants. It can infect a wide range of crops, including many that have high agricultural value. Over the past few years, it has struck the Italian olive industry hard.  

What does it do? 

Xylella infects the internal waterways of the tree, feeding off its resources and choking the flow of water and nutrients to the leaves. This causes scorching of the leaves, withering of the fruit, slowed overall growth of the tree, and eventual death of the host.  

How does it spread? 

Once inside a tree, Xylella spreads by itself. But reaching new hosts requires the help of insects. Fluid-sucking insects, such as spittlebugs and leafhoppers, drink infected nutrients from a tree, move on to another tree, and deposit the bacterium in this new host during the feeding process there. Oftentimes, an infected tree does not show symptoms until it’s far too late to quarantine and prevent further spread.  

Where is Xylella found? 

Beyond olives, Xylella has been known to affect a wide range of important crops: 

• Citrus 
• Coffee 
• Wine & Table Grapes 
• Peaches & Plums 

It is primarily found in the Americas but known infections have occurred in Asia, central Europe, and most importantly for our purposes, in the olive groves of Italy. 

Xylella & Olives 

Olive oil has been produced in the Mediterranean for thousands of years. In that time, growers have endured wars, droughts, and countless other obstacles to maintaining their lifestyle. Now they are facing the destruction of their groves via Xylella. 

10 years of Infection 

The pest was discovered in Italian olive groves almost ten years ago in the south of the country. The effects became clear as trees began to wither and die while olive yields from the region plummeted. Tragically, Xylella has killed many valuable older heirloom olive trees and threatens the existence of several rare olive cultivars with rich and unique histories. 

Fighting Back 

Though we are nearing a decade into the struggle against Xylella, there still isn’t a reliable means to fight the pathogen. Currently, farmers are hyper-vigilant about infection and do their best to eliminate infected individuals. This is not a permanent solution, but it does buy precious time while research continues on a more direct way to combat the disease. 

Hope for the Future

While the challenge presented by Xylella is formidable, we should remember that it is an obstacle that can be overcome. Olive trees are tough and the people that tend to them are tougher. In the face of the millennia-old determination of southern Italy’s olive growers, hope is high that the Xylella pest will soon be another footnote in history.