Oilseed rape growers advised to invest in fungicide and fertiliser

Oilseed rape growers in the south of England should be prepared to invest heavily in fungicides and fertilisers, says Peter Gould of agchem supplier UAP.

“Rape growing is not for the faint-hearted. If growers are not prepared to put the inputs in, either fungicides or nutrition, then they shouldn’t bother with the crop,” he explained to Farmers Weekly on a visit to one of the firm’s trials sites near Winchester.

Disease pressure, particularly stem canker and sclerotinia, had reached “epidemic proportions”, he said, and required at least four sprays to control effectively.

Two autumn sprays were necessary to control phoma leaf spots, which lead to stem cankers. But it didn’t matter too much what product was applied, he noted. The firm was testing Proline, Prosaro, Juventus, Charisma and Kestrel.

In last year’s trials there had been a 0.8t/ha yield response from a two-spray phoma programme over a single treatment, he said.

The lack of a sclerotinia spray in this year’s phoma trial at the site was also showing the pressure from that disease. Two sprays were required to control the disease in high risk areas, which covered most of the south of England, he said. “All the fungicides are protectants, so you need to go in at early flowering to catch the early infection and follow up a couple of weeks later at mid-late flower.”

Prosaro or Proline made good choices for the first spray, he said, while a mix of Filan and Agate was his option for the second spray.

A fifth spray might be necessary in some crops for growth regulation. That would put the cost of fungicide programmes at around £75-80/ha compared with a two-spray strategy costing £40-45/ha.

At current prices of £330-360/t before oil bonus a 1t/ha loss in yield could easily cost £350/ha, he pointed out. “When you’re spending £75/ha that’s a good margin over input costs.”

Which variety?

Varietal resistance to stem canker, for example ES Astrid is rated an eight, was useful up to a point in the region, Mr Gould said. “But don’t choose varieties purely on the basis of canker resistance you have to look at other attributes, such as height and gross output and also match varieties to drilling date and soil type.”

That was why Castille was still a top variety despite it having poorer canker resistance than ES Astrid. “Astrid is useful for early drilling because it is later coming into flower and the better canker resistance is also very useful when drilling early.”

He questioned why growers in the south would want to grow tall hybrids, such as Flash and Excel, even though Flash was top rated for gross output and Excel had a nine rating for stem canker resistance. Both grew very tall and were prone to lodging, he said. “So what’s the point? Growers want easy to combine varieties.”