Flea Beetle attacks on the increase
Cabbage Stem Flea Beetle (CSFB) has placed another hurdle in successful OSR establishment. The experience of most iOSR growers indicates that whilst crops can get away from pest feeding damage in good growing conditions, during in the hot, dry late summer last year heavy losses were incurred.
Furthermore, the intense beetle activity followed by a relatively mild early winter, has left a legacy of extremely high larvae infestation in remaining plants that is likely to further impact on yields.
Martin Parkinson (above) reported instances they were finding where seedlings had emerged, but stalled at cotyledon stage in the dry conditions with evidence of plants being nibbled off at or just below ground level, attributed to CSFB adult or larvae.
It was the first time that some OSR crops at the Cotswold Farm Partnership had been written off, he reported. However, those crops that got up and away were looking vigorous and ready for early nitrogen as soon as conditions allowed, Martin added.
Furthermore, research entomologist and CSFB specialist, Dr Sacha White of ADAS, informed the iOSR group that recent years’ weather conditions, combined with a rapid rise of pyrethroid resistance across the country, is likely to have exacerbated the situation in most areas. Latest monitoring had revealed 90% of CSFB populations sampled showed some degree of resistance, with over a quarter of samples (10 of 38) showing at least 50% resistance, he warned.
“That has made the need for an alternative IPM approach to managing CSFB more important than ever,” he reported.
The situation in 2018, when relatively few beetles were seen around at summer harvest, but then turned into an extremely high pressure autumn, highlighted the need for action every year, he said.
In Norfolk, Chris Eglington detailed he too had lost crops for the first time, due to the combination of conditions and pest pressure. With his precision drilled crops, Chris is prepared to work with low plant populations and still achieve good yields, but this season in some instances even that was not achieved.
St Neots’ grower, Ian Lutey (above), believes the eastern counties OSR area had got so big and beetle pressure so huge that crops have been unable to cope. Now, growers in other areas that had hitherto not suffered so badly, are beginning to bear the brunt. Recent modelling suggests that warm weather in autumn and winter and low spring/summer rainfall have also been shown to increase larvae numbers.