• Helps reduce pest feeding damage
• Affordable and effective option
• More sustainable than insecticides
Growers could combat cabbage stem flea beetle on winter oilseed rape by applying silicon to the crop, say independent agronomists.
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 Chris Coates, an independent agronomist with Sustainable Ag Solutions.
Mr Coates has been recommending silicon in place of insecticides for the last three years. He started by applying Zeme (potassium silicate) in tank-mix with an insecticide, before using silicon alone with no appreciable change in results.
When to apply
“Applications must be made early but should be balanced against the plant presenting a big enough target,” suggests Mr Coates. “Standard cotyledon stage is ideal.”
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.
“If numbers don’t rise enough to merit a separate application, then we’ll wait to tank-mix Zeme with the first herbicide application. At £7/ha, it’s a very affordable, very effective option for controlling this pest without recourse to insecticides.”
Inbuilt resilience
Independent agronomist Dan Lievesely, of DJL Agriculture, has also been exploring silicon’s potential to combat flea beetle. “I’ve always believed that disease and pest pressures come easily to weak crops,” he explains.
“Besides its physical properties, silicon has a role in several plant metabolic functions. Boosting the crop’s inbuilt resilience to attack – whether from pests or pathogens – has to be a more sustainable option.”
Mr Lievesely says he has used various forms of potassium silicate over the last five years. Three applications of Zeme before Christmas also helps nutrient management and reduces lodging, he says.
“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.”
Nitrogen recovery
David Marks, co-founder of Zeme supplier Levity Crop Science, says silicon is vital for phosphate redistribution and trace element transport. “It also improves nitrogen recovery – especially during dry spells.”
Dr Marks describes Zeme 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’s 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.
“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 add lodging protection too.”
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