FINICKY bullfinches have inadvertently led researchers to a pest repellent that could make scarecrows redundant. Tiny amounts of a compound called cinnamamide can put birds, rodents and slugs off eating seeds and crops.
Cinnamamide is the outcome of a project that began 10 years ago when researchers at Britain鈥檚 Ministry of Agriculture, Fisheries and Food were studying bullfinches. The birds eat most types of plant bud but ignore the buds from some varieties of pear tree.
鈥淭he researchers found that buds containing high levels of cinnamic acid and its derivatives were less damaged,鈥� says David Cowan, who heads the team responsible for developing cinnamamide at MAFF鈥檚 Central Science Laboratory in Slough. The researchers tested how repulsive cinnamic acid and related compounds were to the bullfinches and found that cinnamamide, a synthetic derivative, was the most potent.
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Pigeons rejected food spiked with cinnamamide, even when they had nothing else to eat. Just 1 milligram of the 鈥渁ntifeedant鈥� for every gram of feed was enough, says Cowan.
The compound also worked well in field tests with other birds. Chaffinches, greenfinches, great tits and woodpeckers that had spent six weeks eating from peanut feeders were offered the same fare spiked with cinnamamide. 鈥淚t was 100 per cent effective in that no bird ate from treated feeders,鈥� says Cowan.
Rats also avoid food laced with the compound. Given a choice of food laced with cinnamamide or no food at all, their consumption dropped by two-thirds on average. 鈥淚t did slowly increase over time because the rats would otherwise have starved,鈥� says Cowan.
More recently, the researchers have shown that cinnamamide is effective against slugs, which attack cereal crops. Cowan and his colleagues are trying to find out what it is about cinnamamide that puts pests off. He tried the compound himself without any ill effects. 鈥淚t has a faint cinnamon-like taste,鈥� he says.
Cowan hopes that cinnamamide will provide an alternative to mechanical bird-scaring techniques, such as scarecrows and gas guns that fire automatically. These are seldom effective because birds get used to them. He also hopes that cinnamamide will prove more effective and environmentally benign than other synthetic repellents.
The British Technology Group, which commercialises promising inventions, has now patented cinnamamide and is negotiating deals with potential manufacturers.
