With no chemical controls likely to be licensed soon to control pathogenic fungus Mycosphaerella, cucumber growers have been urged to be extra vigilant on hygiene when changing over crops.
Last week's Cucumber Growers' Association (CGA) conference (19 October) heard from Stockbridge Technology Centre science director Dr Martin McPherson who has been leading field trials on the effects of a range of glasshouse hygiene regimes, using spore traps to monitor prevalence of the fungus.
"You might end up losing 30 per cent of your crop to Mycosphaerella, costing you £40,000-50,000 a hectare," he said. "Cleaning up might cost you maybe £1,000-4,000/ha, but the saving is pretty considerable."
A single infected cucumber can yield 300 million spores, making early removal essential, he added.
Independent plant pathologist Dr Aleid Dik said: "Growers in the Netherlands have more fungicides available but even then losses to Mycosphaerella are severe."
Dutch trials have shown some benefit from using the biological control Enzicur - not yet licensed for UK use - from flower and dead leaf picking, and from using so-called "hot knife" or self-sterilising tools. Neither irrigation scheduling nor ultraviolet light were found to be effective controls.
CGA technical officer Derek Hargreaves explained that it would be "another three years" before chemical controls for Mycosphaerella are likely to be available.
McPherson added: "Even when we get some more products, we will have to use them wisely."
Cucumber Growers' Association secretary Derek Hargreaves said the association hopes to meet new farming minister George Eustace to press the case for speedier product approvals.
"We are in a ridiculous situation on availability," he told the group's conference. "The companies are trying. The frustration is with the Chemicals Regulation Directorate."