Scientists have created an agricultural pesticide made from garlic juice concentrate which kills the worms that destroy potato and cabbage crops.
Last September, biologists from the University of Newcastle revealed that garlic juice could kill garden slugs and snails. Now, the same principle is being applied to the tiny worms, called potato cyst nematodes, that destroy £70m of Britain's 37,000 hectares of potato crop annually.
But Ecospray, a company from Thetford in Norfolk which is trying to market the product, is struggling to commercialise the garlic extract for use as a pesticide. Although garlic is a commercial crop, it cannot be certified for use as a pesticide without undergoing tests.
These tests have taken more than four years, and David Sadler-Bridge, the managing director of Ecospray, does not know when they will finish.
"We're hoping to get approval from the Pesticides Safety Directorate (PSD), which does the safety testing, very shortly," he said. "But it also has to be tested by the Health and Safety Executive as a biocide, because it can control red mite which attacks poultry."
Despite garlic's longstanding use in mosquito and other repellents, the PSD has declined to approve its use as a pesticide.
The garlic juice concentrate, which the company calls Nemguard, is dried to form granules and acts against the worms that attack potatoes and crops, including carrots and parsnips.
Experts are divided on how garlic works against the nematodes. One idea is that it boosts the plants' defence systems. Others say some of the chemicals contained in garlic block chemical receptors essential to the nematodes' functioning.
The use of garlic to kill pests is well known and has been co-planted as an anti-pest control for hundreds of years.