15 September 2000

Pigeons prove to be tough research nut

By Andrew Blake

KEEPING hungry pigeons off oilseed rape is proving a stiff challenge for researchers. Four years of HGCA-funded work, costing £120,000, have been only partially successful, admits retiring oilseeds committee chairman Frank Oldfield. The work – to breed a natural deterrent into the crop and develop a spray to protect it – ends this month.

John Innes Research Institute and breeder CPB Twyford produced rape with enhanced glucosinolate levels in the leaves, in the hope that this would be less palatable. Other research involved cinnanamide, a bird-repellent discovered by CSL in the 1980s.

Neither strategy has proved 100% successful and yield results from this years trials are inconclusive. But pigeon damage where the two were combined in a Yorks experiment last winter was cut significantly, says an HGCA report.

"We hope to get more funding from a LINK programme to progress the John Innes work to increase glucosinolate levels in the leaves still further to try to put pigeons off," says Mr Oldfield.

Farming company Velcourt has trialled both approaches. "We tried the John Innes enhanced glucosinolate variety against normal Apex at three sites – in Yorkshire, Norfolk and Wiltshire," says technical director Keith Norman. A two-spray programme of cinnanamide was also tested.

"At each site, we had two fields with alternate 1ha blocks of each. On five of the six fields, we have seen another year when the JI line acted as a total pigeon deterrent or delayed attack. But on the sixth, at York, where we had zero grazing the year before, we saw normal pigeon pressure. The question is whether the birds are becoming tolerant to it, or whether, as the plants get bigger, the glucosinolate levels by March are no longer high enough to put them off."

Despite the HGCA report, which indicates up to 30% less damage by combining the two methods, Mr Norman is less convinced of the sprays potential. "On visual inspection last spring, I couldnt see any real difference between treated and untreated areas," he says.

CPB Twyfords Liz Williams says: "Given a choice, pigeons will go for low glucosinolate varieties. We do have lines with high glucosinolate in the leaves. We can get it in OK and it has no deleterious effect on yield. But I believe the effect on pigeons is only marginal and the work has been shelved." &#42

pigeon prevention

&#8226 Enhanced glucosinolate crops.

&#8226 Cinnanamide spray treatments.

&#8226 Combination cuts damage 30%.

&#8226 Yields this year inconclusive.

&#8226 Vigorous variety best defence?

HGCA-funded research into pigeon deterrence in OSR has so far proved fruitless. Preventing the pest settling in the first place is still the priority.