Drill date options to reduce CSFB damage
Agronomy trials to find solutions to Cabbage Stem Flea Beetle (CSFB) losses had shown little or no differences between current varieties, and very limited benefit in increasing seed rates to counter pest activity, according to ADAS entomologist, Sacha White.
In fact, Sacha (below) told the iOSR grower group meeting that the trials had shown increased seed rates led to far higher total larvae numbers and consequently higher long-term populations.
There could be potential for breeding varieties selected to have low levels of glucosinolate - the precursor to making seedlings attractive to CSFB - however the trait would also be likely to make them more attractive to slugs.
He pointed out that August drilling appeared to reduce the impact of adult feeding damage, typically as plants grow away faster.
However, delaying drilling until September resulted in less larvae presence in the growing crop, primarily as the crop is exposed to egg hatching and infestation for less time.
That is important, he believed, since research has shown that, in good growing conditions, even small OSR seedlings can withstand intense and repeated adult feeding damage. But larvae numbers have a far greater impact on yield.
Survey data had shown an infestation of just five larvae could result in 0.5 t/ha yield loss, and a tonne loss from 15 larvae per plant; when in reality far higher numbers could often be found in crops.
The implication is that delayed sowing may have more to offer by way of preventing larvae damage. However, the iOSR growers highlighted the practical risks to get a late crop successfully established, which was unlikely to find favour for September drilling.
Trials for later sowing on the iOSR Focus Site, drilled on the 20 September, were showing plenty of plants at the end of January (above), but at small growth stages.
Providing they survive pigeon feeding and high Phoma pressure, CSFB numbers will be fully assessed in the spring and compared to levels in earlier sowings, reported Syngen ta Technical Manager, Georgina Wood.