The timing of disease control sprays is the next challenge for our two High 5 oilseed rape growers, as they continue with their efforts to produce 5t/ha crops. Louise Impey gets an update

Tim Goodman
North Hill Farm, Salisbury

Oilseed rape crops are still growing at Wilton Estates, near Salisbury, aided by the mild conditions and warm soils, with plants now between 4 and 8 true leaves.

Farm manager Tim Goodman reports some variation in growth stages, depending on sowing date and the availability of moisture at drilling, but is pleased with how his 400ha of oilseed rape is looking ahead of the winter.

Broad-leaved weed control was done on time and according to plan, with the use of pre-emergence Katamaran Turbo (dimethenamid + metazachlor + quinmerac), while a follow-up graminicide was also applied. “I don’t envisage having to do any more on broad-leaved weeds this side of Christmas, except for specific areas where charlock is a problem,” he notes.

Soil temperatures are still too high for planned propyzamide applications, which are normally made in early November for blackgrass control, he adds. “This year, the crop canopy is also too big. It needs knocking back a bit by some colder weather before we can spray.”

For more on this: See all of the articles on High 5 OSR yields

Phoma levels are building, but remain below thresholds, he continues. “We’ve had the rainfall and the temperatures to favour the disease, but our varieties have good resistance and there’s no great urgency.”

He expects that the first fungicide will be applied in the next 7-10 days, when final fungicide product choice will be based on disease levels and whether the crop needs some growth regulation. “We’ll make that decision much nearer the time.”

That first fungicide application may fit in with the optimum propyzamide timing, he acknowledges, providing soil temperatures have fallen. Given that it is already November, the second fungicide application is likely to be made early in the new year.

Otherwise, his crops will receive boron before floret initiation takes place and may have an insecticide for cabbage stem flea beetle and leaf miner, if threshold levels are reached.

“October did turn out to be a wet month,” says Mr Goodman. “But fortunately we are not up against the wall and don’t need to rush out with the sprayer.”

Andrew Gloag
Busby House, North Yorkshire

Andrew Gloag is encouraged by the rapid development of his oilseed rape crop, most of which is now at four to five true leaves.

“Considering its late start and backwards establishment from a mid-September drilling date, it’s grown very well. Of course, the mild conditions throughout October have helped.”

He is now contemplating the first fungicide application, which will be driven by the need for phoma control. “Crops are generally clean at the moment, but quite small, so phoma is the main threat. But we will be looking for some light leaf spot activity too.”

Cooler temperatures would allow him to combine this first fungicide with the propyzamide application for blackgrass control, which needs falling soil temperatures for best results. “Soil conditions are good for travelling and we would hope to be able to put on the boron and Nutriphite at the same time.”

In a normal year, Mr Gloag would make a split autumn application of prothioconazole, with both sprays going on before Christmas. “But this year, we’ll do the first one in the next 10 days or so, with the follow-up likely to be just before stem extension in the spring.”

Weed control results from pre-emergence metazachlor and a post-emergence graminicide have been very good and have dealt with the volunteers, he reports. “We may have to go in with some Galera (clopyralid + picloram) later on for sow thistle, but that will be all.”

Using propyzamide does add significantly to the costs of rape growing, he comments. “But if you spread it over the three crops in the rotation, it’s only an extra £5/ha per crop. And we need to use different modes of action against blackgrass to keep weed populations down.”