Well-chosen, correctly-timed spring fungicides, in combination with later-applied nitrogen, can boost winter oilseed rape margins even in the absence of sclerotinia.
The results from Hutchinson’s trials last season suggest green-bud applications are the most effective as a single timing for fungicides, but split applications could be even more beneficial.
The trials were set up after the company had seen yield responses from fungicides applied at the green bud timing in previous seasons, the firm’s technical manager Dick Neale says. “It needed further investigation.”
Commercial crops of Castille and Lioness, which received most of their nitrogen at early flowering, were treated with a range of fungicides at green bud, yellow bud, or at 50% of flowers open, or in sequence at the first two timings. For the single applications the same rates were used at each timing.
“The highest single application yield in each case came from the green bud timing and achieved an average margin over input costs (MOIC) of £53/ha. Applied at the latest timing, the same input achieved a margin of only £3/ha,” Mr Neale says.
Priori Xtra gave consistently higher yield and margin compared to all other treatments, he notes. “Adding cyproconazole to the Amistar clearly adds growth regulation and delivers more yield.”
The split applications of various products were investigated to see if accumulative doses were beneficial.
Doubling the dose applied dramatically lowered the MOIC, but an application of two reduced doses boosted yield and MOIC beyond any single application. Exactly where the yield responses came from is unclear, he admits.
“Lodging wasn’t a yield-determining factor in these trials, although the results gave a clear indication of which products – for example, cyproconazole in Priori and tebuconazole in Prosaro – are effective in reducing stem height from spring application,” says Mr Neale. Metconazole, which was not tested, would also have a growth regulatory effect, he acknowledges.
Sclerotinia was also absent, he notes. “I think the responses came simply from better green leaf retention.”
The reliability of the returns should increase grower confidence on input decisions, he says. “In these trials 91% of applications gave a positive MOIC.”
A sequence of Prosaro and Priori Xtra gave the highest yield and margin responses of 0.63t/ha and £56/ha respectively. “I have as much faith in Prosaro as Priori Xtra.”
A new Syngenta coded pgr/fungicide product, targeted specifically at winter oilseed rape, was also evaluated. “It is a true pgr with a fungicide mixed in rather than a fungicide with some pgr activity,” says Mr Neale.
“As the cost is not yet known, we can’t apply a margin figure and further evaluation is needed. But it produced the highest yield in both trials from a green bud application in conjunction with Priori Xtra at yellow bud.
“The key point to remember is that no sclerotinia pressure arose in these trials, and the early timing, while optimum for delivering yield, would not extend long enough into flowering to control the disease in a high pressure year. This is why we always advise a split application.”