Applying a silicon product to oilseed rape (OSR) crops could help mitigate attacks from cabbage stem flea beetle, say two agronomists.

Cabbage stem flea beetle is the number one pest of oilseed rape with adults devouring newly establishing OSR plants.

Plants use silicon – the primary constituent of glass – as a physical barrier against attacks by pests and pathogens, laying down a hard crystal layer of “opals” within the leaf cuticle.

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This means one way to help make plants better able to withstand attack is to increase silicon levels, and one independent agronomist has found that applying two to three applications of silicon have been sufficient to reduce the feeding damage from the key pest.

Based in Yorkshire, Sustainable Ag Solutions’ Chris Coates has been recommending silicon in place of insecticides for the past three years, after attending a farmer meeting where the idea was first floated.

In early usage, Chris applied Zeme (potassium silicate) in tank-mix with an insecticide, before stripping applications back to silicon alone with no appreciable change in results.

“Applications must be made early, but should be balanced against the plant presenting a big enough target. Standard cotyledon stage is ideal,” Chris suggests.

Prevention

As the silicon is not a control for flea beetle, Chris says applications should be made prophylactically.

“There’s been very little flea beetle damage so far this year, which I suspect is down to the wet weather having disrupted insects’ lifecycles.

“Now we’re monitoring flea beetle levels and will be primed to make applications if numbers rise.”

He adds that if numbers don’t rise enough to merit a separate application, then he will wait to tank-mix the product with the first herbicide application.

“At £7/ha, it’s a very affordable, very effective option for controlling this pest without recourse to insecticides.”

A similar sentiment – transitioning farmers away from harsher inputs – lay behind Dan Lievesley’s exploration of silicon.

“I’ve always believed that disease and pest pressures come easily to weak crops,” explains the independent agronomist from DJL Agriculture.

“Besides its physical properties, silicon has a role in several plant metabolic functions.

“Boosting the crop’s inbuilt resilience to attack, be it from pests or pathogens, and reducing abiotic and biotic stress, has to be a more sustainable option.”

Other benefits

Dan has used various forms of potassium silicate over the past five years, finding it a good tool to manage not just flea beetle attack, but also lodging and nutrient management.

“My recommendation centres on three applications of Zeme before Christmas,” he explains.

“The first at cotyledon stage, the second at 1-2 true leaves, and the third as the last application once you’ve applied Kerb (propyzamide).

“We’ve avoided insecticides completely since starting to use silicon.”

Dr David Marks, co-founder of Levity Crop Science which produces Zeme, says silicon – while rarely used as a crop input – brings considerable benefit to crop health.

“Not only is it implicated in production of anti-stress hormones and antioxidants, silicon’s also vital for phosphate redistribution and trace element transport.

“It also improves crops’ nitrogen recovery abilities, especially during dry spells when soil nitrogen availability can be very low.”