CHOOSING the right fungicide for use on oilseed rape crops has been making the difference between good and bad yields in what has been a difficult year for the crop in Scotland.

According to Catriona Bancroft, an agronomist with Wallace of Kelso: “Temperate, wet weather is the worst when it comes to disease. Phoma can occasionally be a problem, but light leaf spot is the biggest challenge in this area.

“Phoma is creeping further north and we have a challenge about one year in three. This year, we haven’t seen much, but light leaf spot was a big problem. Any untreated crops were plastered in the disease by February.”

Good establishment is the key to success, but this year's Scottish crops sat in wet ground throughout much of the winter. “It then turned really dry in May and June, which stressed the crops badly – where the crops didn’t root well they died off early; it was very easy to spot,” she pointed out.

Ensuring crops get their roots down early is becoming ever more important, she argued. “This year we either had torrential rain or drought, which isn’t good for crops. It’s all about maximising plant health to produce a good core plant.”

Mrs Bancroft said there is now no standard method to successfully establishing oilseed rape. “I have farmers ploughing and drilling, min-tilling, and drilling behind the legs using air-seeders on cultivators or subsoilers. There are a huge number of ways to produce good results, the secret is to find a method that is reliable in varied conditions on your ground.”

One of the most successful options this year was direct drilling oilseed rape behind a subsoiler, something which one of Mrs Bancroft’s clients in Berwickshire chose to do. He sprayed off the stubble prior to drilling and used a seed rate of 2kg/ha in 52cm wide bands.

“Initially it looked as though it was drilled at too wide a spacing, but by the time we came to harvest, the canopy had filled all available space,” she said. “With this season’s strong winds, a thick canopy deterred movement and limited shedding.”

Fertiliser application methods and rates are equally as varied as establishment techniques, she added. “Many farmers are ploughing in hen manure or muck to try to improve oilseed rape establishment prior to our normally harsh Scottish winters and some farmers prefer to apply 30kg of nitrogen in the autumn.”

The direct drilling Berwickshire farmer applied 7.20.0 liquid fertiliser in precision bands at drilling, with 190kg/ha of nitrogen in total over the year. “He made the drill himself and commented in the spring how good the rooting was – in fact, he won the new entrant category in the local crop competition and I think the rooting was a factor in that.”

Placing the fertiliser directly where the plant can access it has worked incredibly well, explained Mrs Bancroft. “It’s very effective. The fertiliser was immediately available to the plant but with no fertiliser in the spacing between rows the weed pressure stayed low.”

Once the crop is established, it is essential that farmers apply a light leaf spot fungicide in the autumn because pressure is always high, she said. “Phoma is also becoming more of a problem in Northumberland and the Borders. With the loss of the triazole fungicide, flusilazole and the threatened ban by Europe of all triazoles, we have been concerned what would replace this chemistry.

"Du Pont's Frelizon [penthiopyrad and picoxystrobin] has proven to be the non-triazole answer we were looking for.” She recommended a half rate of it in the autumn, with a triazole (prochloraz and tebuconazole) mix in the spring, followed by a flowering spray of Galileo (picoxystrobin) to protect against sclerotinia and prolong flowering.

However, because of limited spraying days, some did not manage to get sprays on last autumn at all. “I had one client who couldn’t get on in the autumn as it was too wet – he delayed the Frelizon until the spring and it gave good light leaf spot control,” said Mrs Bancroft.

“He followed it up with metconazole and mepiquat chloride which has a plant growth regulatory effect and this improved the depth of the canopy.”

An unexpected bonus of using Frelizon in the autumn is the improved rooting, she added. “You certainly get 25-30% more root mass. You can visibly see the difference, which is remarkable really. It’s the small roots more than the tap roof itself, but as soon as we’d sprayed the crops never looked back.”