Submitted by BethBradshaw on 28 November 2017
Last month, the first UK case of Fusarium lettuce wilt was found at a farm in Lancashire.
Lettuce wilt is caused by Fusarium oxysporum f.sp. lactucae, a filamentous fungus that causes wilting, decay and death of plants. The fungus invades the plant via its roots before spreading into its xylem (water vessels) and phloem (sap vessels), which become completely blocked. When the plant finally dies, the fungus consumes all of its tissues and produces spores to infect neighbouring plants.
First described in Japan in 1955, it has since spread across Asia, North America and more recently mainland Europe. It is thought that the disease spreads between continents via infected seeds, but it can also spread locally in soil attached to farm machinery, water or plant matter. Italy has been particularly hard hit, with up to 70% of lettuce crops in contaminated fields being lost. Until now the UK has been less affected as lettuces sold in the UK are mostly grown domestically, but if the disease takes hold it could cause devastating losses to British farmers. Alarmingly, the aggressive ‘Race 4’ strain found in Lancashire cannot be controlled with either pesticides or soil sterilisation, and the spores can survive in the soil and crop debris for long periods of time.
There are many different strains of Fusarium wilt, which each infect different plants. One called ‘Panama disease’ is the most serious disease of bananas, threatening up to 80% of the world’s supply. Others infect weeds and have been proposed as a long-acting chemical-free herbicide. It was even suggested by the White House as an ‘Agent Green’ for halting coca leaf production by Colombian guerrillas, although the plan was ultimately rejected by the Colombian government and the United Nations.
Fusarium does not commonly infect humans, but can occasionally cause keratitis of the cornea via eye scratches or contaminated contact lenses.
Read more at Fusariumwilt.org
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