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Diseases of plants: Citrus canker
Citrus canker is a serious bacterial disease of citrus trees including grapefruit, lemons, limes and oranges. It reduces the growth of new fruit and spoils healthy fruit. Outbreaks of this disease have been eradicated from Queensland and the Northern Territory at great cost to industry and growers. Quarantine needs your help to detect any future outbreaks.
Keep a Top Watch
Watch out for scabby marks on leaves and fruit, and if you think you see evidence of citrus canker, contact your Quarantine officer for advice. The disease can spread quickly to healthy plants, so protect our citrus industry by being watchful.
Profile: The disease attacks the leaves, twigs and fruit of citrus trees. It causes the leaves to drop and fruit to fall to the ground before it ripens. Growth of young trees can be severely affected because of damage to new shoots.
Identification: The disease affects any part of the citrus tree growing above the ground. Ugly, warty, rusty-brown spots (cankers) form on the leaves, twigs and shoots. The cankers on leaves develop a distinctive bright yellow halo around them. Scabby cankers also appear on the fruit.
Photos below: The Citrus canker disease attacks the leaves, twigs and fruit. The cankers develop a distinctive bright yellow halo. Warty, rusty-brown spots form on twigs, shoots and fruit.
Distribution: Citrus canker is most severe in hot, wet areas - strong winds and rain help it to spread. The disease is common in Indonesia and Papua New Guinea.
Threat: Citrus canker can spread quickly and has the potential to devastate Australia’s healthy citrus industry. Because the fruit is scarred, it can’t be sold. The costs to growers and consumers increase, while returns are lowered, threatening jobs and income.
Quarantine: Extensive monitoring and controls are in place to prevent citrus canker from entering and spreading in Australia. Quarantine is the only way to stop the disease from establishing in Australia, and AQIS is working with growers to raise awareness.