The role of plant growth regulators (PGRs) used alongside that of fungicides can deliver cost benefits that might not be as appreciated as it should.
That was one of the key messages from a briefing held by B ASF, last week, where its head of business, Steve Dennis, pointed out that not using a PGR as part of a spray strategy was taking an unnecessary risk with the crop.
"We all take calculated risks every day, but what should our attitude be with our crops – insurance, or investment," he argued.
"Lodging typically occurs every three or four years and when it happens, there are serious consequences for the crop in terms of yield and quality. Not using PGRS means that growers are taking a risk.
"At full dose rate, this could cost £10 per ha, but the risk of going in too low with rates is far greater than going with too high a rate in terms of cost benefit. The risk is four times greater with a low rate, than it is with a high rate."
Matched to a well-chosen fungicide, like BASF's Revystar, a PGR has been shown to have a significant impact on return on investment.
That point was echoed by BASF's Stuart Kevis, who pointed out that in high lodging years up to 20% of the wheat area could be affected, with a subsequent considerable loss in income.
"And the economic loss is greatest when crops lodge early, with up to 75% of yield lost if crops lodge at ear emergence," he pointed out. "Later lodging has less effect on yield, but impairs quality characteristics such as Hagberg falling number."
These crops often require extra drying, which can cost £3-£7.50 per tonne. He pointed to results from using MedaxMax PGR which had been shown to increase root mass, as well as shorten the crop's stems.
"Bigger, better rooting allows the crop to access more available nutrients leading to a more healthy crop and better yield," he argued.
The plant on the right had been the result of a spray of 0.6kg/ha at GS31/32 against an untreated plant on the left
In the wake of increasing disease resistance to certain fungicides and their modes of action, Mr Dennis said growers should work hard at making the most of Revysol's stable position by careful use and sensible use of other modes of action to reduce the risk of building resistance.
Jon Helliwell, BASF and Rebecca Joynt, from ADAS, both pointed out that septoria remained the No 1 enemy for wheat growers. And, despite a low disease pressure year last year the co-formulation fungicide Revystar XE showed up well in trials to control it and yellow rust.
Lodging and brackling impacts
Lodging and brackling risks were highlighted by ADAS' Pete Berry
Pete Berry, of Adas, pointed out that:
• Increasing seed rate by 100 seeds/m2 was equivalent to reducing varietal lodging resistance score to stem/root lodging by 1.5 to 2 points
• Increasing N fertiliser rate by 50 kg/ha reduced the score to stem lodging by 1 point and root lodging by 0.5 points
• Delaying the first N split from seed bed to tillering/ GS30 was equivalent to increasing the score to stem lodging by at least 2 points, but also reduced yield
• Using a PGR to reduce crop height by 5cm would increase the varietal lodging resistance score by almost one point
• Larger canopy size at GS30 was also associated with greater lodging risk.
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