Britain’s winter oilseed rape (WOSR) area could surge by about 20% this autumn, driven by strong OSR prices and after two years of generally low levels of cabbage stem flea beetle (CSFB). But flea beetle has not vanished, so carefully consider your attitude to risk.
That was a key message from a recent trials hub open day of agronomy firm ProCam, held at Stockbridge Technology Centre, Cawood in Yorkshire.
Speaking at the event, ProCam seed manager, Lee Harker, said: “There are two basic approaches to establishing WOSR in light of flea beetle risks. Either, establish a crop as cheaply as possible and see if it avoids CSFB before spending any money on it. Or, follow a proactive strategy of planting a vigorous variety with the aim of establishing a stronger crop that is more resilient to flea beetle damage and with higher potential yield.
“With the former approach, one option is to plant home-saved seed. However, it does not take many seeds of brassica weeds or volunteer OSR in home-saved samples to push erucic acid levels in the harvested crop above the 2% legal limit. As an alternative, therefore, consider buying new seed but of a cheaper WOSR variety and treating it with a seed treatment for faster germination.
“The conventional variety Keeper, for example, is a large-seeded variety for good seed to soil contact, and even when treated with Sylas ST seed treatment could cost less than £100/ha to establish, half of which is in cultivation and drilling costs. If it establishes well, you have the potential for a high gross margin WOSR crop. If it does not, you can consider writing it off and replacing it with a suitable alternative. The cultivation cost will not be wasted because it will contribute towards the seedbed for the replacement crop.”
Where growers are following the second approach of proactively establishing a crop for maximum performance, Mr Harker urged planting hybrid WOSR varieties for their hybrid vigour.
He said: “When WOSR gets to two true leaves it becomes more resilient to adult CSFB damage, so you want to get it there as quickly as possible. By five leaves, WOSR should also be building a good root mass, and healthy plant stands with thicker root collars are more resilient to CSFB larvae.
“Other factors to take into account as well as CSFB are whether the field has a problem with brassica weeds or WOSR volunteers that could cause high erucic acid levels, and whether the field has a problem with clubroot.
“If brassica weeds or WOSR volunteers are a problem, then consider a Clearfield hybrid so you can remove them. If clubroot is a problem, then look for a hybrid that is recommended for clubroot-infested land. You may pay a slight yield penalty compared with some other varieties, but clubroot is an increasing problem and, if you have it, you need to manage it.
“If you do not need a Clearfield hybrid and clubroot is not an issue, then consider a high-output hybrid such as LG Areti. This has shown excellent establishment, but does not grow too proud over winter so is more resilient to frost damage. Plus, it has exceptional spring vigour and good levels of disease resistance.”