Applying silicon to oilseed rape crops could help to reduce cabbage stem flea beetle damage, field trials suggest.
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.
“Two to three applications of silicon have been sufficient to reduce the feeding damage appreciably,” says Sustainable Ag Solutions’ Chris Coates from Yorkshire.
Growing confidence
The independent agronomist has been recommending silicon for the past three years, after attending a farmer meeting where the idea was first floated, he explains. In early usage, Chris applied Zeme (potassium silicate) alongside an insecticide, before stripping applications back to silicon alone with no appreciable change in results.
“Applications have to be made early, but should be balanced against the plant presenting a big enough target – standard cotyledon stage is ideal,” he suggests.
As silicon isn’t a control for CSFB, Chris says applications should be made prophylactically. “There’s been very little CSFB damage so far this year, which I suspect is down to the wet weather having disrupted the insect’s lifecycle. Now we’re monitoring CSFB levels and will be primed to make applications if numbers rise.
“If numbers don’t increase enough to merit a separate application, then we’ll wait to tank-mix Zeme with the first herbicide application,” he adds. According to Chris, at £7/ha, it’s an affordable and effective option for controlling the pest.
Further independent support
Moving away from synthetic plant production products is behind DJL Agriculture’s Dan Lievesley’s exploration of silicon. “I’ve always believed that disease and pest pressures come easily to weak crops,” explains the independent agronomist.
“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.”
Dan’s used various forms of potassium silicate during the past five years, and says he finds it a good tool to manage not just CSFB, but also lodging and nutrient management.
“My recommendation centres on three applications of Zeme before Christmas – 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,” he says.
Additional benefits
Dr David Marks, co-founder of Levity Crop Science, adds that 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 vital for phosphate redistribution and trace element transport.
“It also improves a crops’ nitrogen recovery abilities, especially during dry spells when soil nitrogen availability can be very low.”
David describes Zeme, Levity’s silicon product, as potassium silicate ‘on steroids’. “Standard foliar silicon always has some effect, but because the plant quickly locks it away into opals – a one-way process – it becomes unavailable to the plant again.
“Zeme has been formulated with naturally occurring silicon transporters that allow the silicon to move within the xylem, so the plant can actively manage absorption and distribution,” he explains.
This ensures sufficient silicon is available for metabolic functions, while allowing the plant to lay down the opals that provide the all-important pest feeding protection.
“Once in the stem and leaves, the opals confer structural strength too, which is why autumn silicon applications will last through the season to provide additional lodging protection,” concludes David.
