How a Tiny Island Stopped a Big Threat: The Citrus Canker Success Story

In 1984, citrus canker—caused by the highly contagious bacterium Xanthomonas citri—was detected on a handful of backyard trees on Thursday Island, a small community in Queensland’s Torres Strait [1]. This was no minor concern: left unchecked, citrus canker can spread rapidly and cause major damage to citrus industries, both commercial and backyard.

But what followed was a plant disease success story. Through swift action, rigorous containment, and some innovative surveillance techniques, the disease was completely eradicated within four years

Central to this effort was the strategic use of potted West Indian lime seedlings as “bait plants.” These plants are exceptionally susceptible to citrus canker and were placed beneath larger citrus trees and in areas near previous outbreaks. This allowed plant pathologists to detect the presence of the pathogen—even when symptoms were not yet visible on mature trees. In one critical case, a bait plant helped identify an infected tree that had shown no obvious signs of disease, enabling authorities to intervene before further spread occurred.

In addition to this clever technique, authorities implemented a strict quarantine on all citrus movements from the island, destroyed infected and nearby citrus trees, and conducted repeated surveys across Thursday Island and neighbouring islands. A public awareness campaign ensured local residents understood the importance of reporting symptoms and avoiding plant movement.

After the final detection in 1986 (from regrowth on an incompletely removed stump), no further signs of the disease were found. Following years of intensive monitoring—using bait plants and repeated inspections—citrus canker was officially declared eradicated from Thursday Island in 1988.

This case remains a powerful example of effective plant disease management. It shows how early detection and rapid action can help eliminate serious biosecurity threats–before they take hold.