Seville’s marmalade oranges under threat from deadly yellow dragon disease
Oranges are to Seville what cherry blossom is to Kyoto, but the city is having to take preventive measures to protect its 48,000 orange trees from deadly bacteria that have already devastated citrus crops in Asia, Latin America and the US.
The EU’s Life for Citrus campaign, which includes Spain, Portugal, France and Italy, is developing strategies to stop the spread of huanglongbing (HLB), Mandarin for “citrus greening”, also known as yellow dragon disease. Caused by the bacteria Candidatus liberibacter, it is spread by insects and can completely destroy a citrus tree within five years.
The infestation has already reached epidemic levels in 48 Asian countries and 53 African states, as well as Brazil and the US. It was detected in China in 1943, in Africa in 1947 and by 2005 had begun to devastate Florida’s orange groves. It has yet to arrive in Europe but the insect that carries it has.
“One of the vectors, Trioza eryteae, has already been detected in the Canaries, Portugal and Galicia in north-west Spain, but not the bacteria,” says Francisco Arenas, head of Las Torres research institute in Andalucía, southern Spain. “The problem is that, once the vector arrives, sooner or later the disease comes too.”
The first sign that a tree has been infected is yellowing and distorted leaves. Then the tree produces less fruit and, within five years, is dead. There is, as yet, no treatment available; the only answer is to dig up and replant the trees or take preventive measures.
Seville city council and Life for Citrus have embarked on a pilot scheme to encourage the spread of insects and birds that prey on the pest that spreads the disease, as part of a trend of working with nature rather than against it.
In Seville’s Buhaira park, an
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