A new oilseed rape fungicide will be available this autumn providing vital protection against phoma and the growing problem of light leaf spot.

The SDHI product Refinzar contains the same active ingredient penthiopyrad as cereal fungicide Vertisan, and so offers a different mode of action against some of the biggest yield-robbing diseases in oilseed rape.

Adas plant pathologist Faye Ritchie believes the alternative chemistry to the widely used azoles, is a big boost to growers as they have to rely on fewer disease controlling products.

“It has performed well in trials showing significant reductions in light leaf spot and phoma infections and has the added bonus of offering different chemistry,” she said at a launch briefing.

The new product from the agrichemical giant DuPont is a mix of the SDHI and the strobulurin picoxystrobin and can be applied early in the autumn to tackle phoma and has shown good yield responses in trials

The dual ability to help control light leaf spot as well, is also seen as a much needed lift to growers with this once northern disease spreading rapidly across the UK.

“Having previously shown effects in wheat, I carried out trials on oilseed rape crops and the results were quite astonishing.”
Stephen Rossall, Nottingham University

“Light leaf spot has been the key disease for many this year with levels reaching some of the highest we have ever seen,” she explained.

The control of light leaf spot relies on a programmed approach, with Refinzar providing a break in the reliance on azole chemistry.

Areas of England and Wales have experienced severe infections of the disease which can see yield penalties of up to 1t/ha, and Dr Ritchie pointed out that many growers are likely to see high levels of light leaf spot this autumn.

Rooting

The new SDHI product could also see benefits to rooting in oilseed rape crops Stephen Rossall, plant pathologist at Nottingham University, has carried out trial work looking at the effect of penthiopyrad on the crop.

“Having previously shown effects in wheat, I carried out trials on oilseed rape crops and the results were quite astonishing,” he said.

Significant differences in the lateral branches of the tap root were discovered, when using the penthiopyrad-based fungicide and comparing it with other commonly used ones.

Monitoring the plant up to leaf stage four, Dr Rossall said the improved rooting was very clear visually and also once he weighed the dry matter of the roots.

Further work is set to be carried out, looking at the benefits in the field and Dr Rossall believes if the results are mirrored in these situations the benefits for crop establishment could provide a big bonus to growers.

“It is a characteristic that could benefit crop establishment helping with better water and nutrient uptake and providing better anchorage,” he said.

Dr Rossall pointed out that in future challenging seasons and when growers are facing increasing pressure from blackgrass, the perceived improved rooting benefits could be important to growers, helping crop competition and early vigour.

DuPont fungicide product manager Mike Ashworth agrees the possible rooting benefits could prove useful for the future as they could help crops deal with drought scenarios.

He believes the new product release will help fill a void in the market following the withdrawal of flusilazole.

“The two components of the product have demonstrated they are a perfect combination with the penthiopyrad effective against phoma and the picoxystrobin effective against light leaf spot,” he said.

With no growth regulator in the product, growers will also have the greater benefit of letting the plant establish itself well and combat any difficulties it encounters early on in the autumn.

“One of the main things with oilseed rape is getting it established well, so unless it is particularly forward going into the winter and growers feel it needs pulling back a bit, this will offer a great option,” said Mr Ashworth.

The earliest application will be at two leaves with the latest coming at stem elongation. However, Mr Ashworth predicts most will use it early on in the autumn taking advantage of any possible rooting benefits.

Growers will be able to make one application a season and are reminded to allow for an 8m aquatic buffer zone, or 1m if the ditch is dry.

There will also be the opportunity of tank mixing with a range of insecticides and graminicides, according to Mr Ashworth with no known problems.