Canary Islands vs. Citrus Greening: A Wake-Up Call for Europe

Citrus greening disease is the most devastating threat facing citrus crops worldwide. Spread by small sap-sucking insects known as psyllids, the disease causes trees to produce misshapen, bitter fruit, gradually decline, and eventually die. Once it takes hold, there is no cure, and infected areas face long-term economic and ecological damage.

Florida is a stark example. Since citrus greening disease was detected there in 2005, orange production has fallen by over 23%, costing billions in economic losses and tens of thousands of jobs [1].

Now, Europe faces a growing risk. The African citrus psyllid (Trioza erytreae), one of the known carriers of the bacteria that cause citrus greening disease, has spread across parts of Spain and Portugal since it was first detected in 2014 [2]. While the disease itself hasn’t yet reached the European mainland, the presence of the vector means the threat is real—and potentially imminent.

But there is reason for hope, thanks to a remarkable success story from the Canary Islands.

After Trioza erytreae appeared there in 2002 and became widespread, decision-makers acted quickly. In 2018, they began a biological control program by releasing a tiny wasp called Tamarixia dryi. This wasp is nature’s own solution: it specifically targets and kills the pest by laying its eggs on the young insects. The wasps were released in a pesticide-free orchard on Tenerife—and the results were dramatic.

Within a year, the wasps had spread to four neighboring islands. In just two years, the percentage of sites infested with the psyllid dropped from more than 80% to under 5% in the main citrus-growing islands of Tenerife, La Palma, and Gran Canaria [3].

The takeaway is clear: early, science-based intervention can stop invasive pests before they cause irreversible damage. Had this approach been implemented sooner, the spread of Trioza erytreae into mainland Europe might have been prevented [3].