Planting oilseed rape (OSR) later and using biostimulant treatments has proved an effective strategy against cabbage stem flea beetle (CSFB). Trials carried out on RGT Black Moon and RGT Paparazzi by biostimulant specialist Orion FT have shown that plants treated with silicon biostimulants Deneb and Sirius had wider stems, sustained less damage and had a higher plant count.

“Using vigorous, fast establishing hybrids that are better suited to late drilling is becoming more popular. However, the threat of CSFB does not diminish entirely for those looking to delay. Our trial showed OSR that was treated with silicon established thicker and wider stems and a thicker cuticle that made the plant less appealing to CSFB,” says Orion’s research and development agronomist Kate Finlayson.

Planting later reduces larval pressure by delaying emergence until after adult CSFB have laid eggs. This, combined with cooler conditions, has helped growers to slow beetle damage. However, with the threat still apparent, Orion’s trial has shown that taking a biological approach can improve plant resilience and reduce reliance on expensive chemical treatments.

“Planting later increases the risk that plants will not establish fast enough to endure early cold weather. Biostimulants help mitigate this risk by helping OSR to take up more nutrients faster. Silicon helps to improve the nutrient availability in OSR, enabling the plant to establish faster with stronger stems and deeper seeking roots,” she says.

In trials, OSR treated with a 0.25 l/ha and 0.5 l/ha Deneb showed stem widths were significantly increased by 38% and 56% respectively after two and four weeks of treatment. While the average CSFB damage for both applications was similar, after two weeks the 0.5 l/ha application showed a smaller range of CSFB damage after four weeks.

“It is not just flea beetle damage that silicon helps with. We have carried out similar trials with slugs which also saw a significant reduction in plant damage. By making OSR stronger using biostimulants it helps to toughen and thicken the cuticle and increase leaf hair density. It also increases phytoliths in the plant which make it less attractive to insect herbivory,” she says.

For those planning to plant OSR later, the risk of CSFB is lower, but focusing on plant health to see the crop establish fast enough is still a challenge.

“Planting late is emerging as a good strategy in the UK, but OSR establishment can be boosted by biostimulants to help it against pests and to establish faster to stand up to cold and challenging growing conditions,” concludes Finlayson.