Increase in OSR area to blame for rising BCN numbers

Researchers have reported higher numbers of beet cyst nematodes (BCN) in soils tested last year, but new findings suggest choosing a tolerant variety could help minimise this build-up.

According to Broom’s Barn crop protection leader Mark Stevens, the pest could be being favoured by a larger area of oilseed rape in the rotation which is also a host. The pest can cause 30-40% yield loss through direct damage to the root.

His advice is for growers is to be increasingly vigilant during the summer months and not to confuse symptoms of rhizomania with those of the nematode.

“Seen from June onwards, beet cyst nematode damage to the roots leads to wilting of crops similar to that seen in rhizomania. The key visual difference is the appearance of lemon shaped cysts on the lateral roots,” he said.

Last year, Broom’s Barn carried out joint BBRO-funded research with British Sugar and NIAB TAG into the ability of tolerant varieties to resist BCN.

Varieties known to offer some level of tolerance were grown side by side in one tonne boxes to see whether they could be used to minimise build up of nematode populations in soils. These included commercially available varieties Annouschka KWS and Sentinel together with seven other RL entries compared alongside susceptible variety Bullfinch.

The research teams measured the numbers of BCN eggs in the soil before and after the varieties had been grown – to give a final population: initial population index or pf/pi.

Results showed that growing a non-tolerant variety such as Bullfinch served as a host for the pest and population levels in the soil rose. In this trial the pf/pi was 6.6 times higher after harvest.

In comparison, Annouschka KWS had a pf/pi of 1.3, showing a slight population increase, whereas Sentinel’s score of 5.9 suggested that the variety is less effective at reducing pest levels in the longer term.