It’s difficult to get beyond the words cabbage stem flea beetle when oilseed rape is mentioned, but the high number seen this year are the result of a ‘perfect storm’ over the last 18 months - warm winter 2018, dry summer & early autumn 2018, warm winter 2019. We just need a weather break to help us out, and we’re also beginning to learn more about this pest.
ADAS research shows there are lower larval numbers in later drilled crops which is the focus for yield loss. But these crops can be more prone to adult attack. Fast, even crop establishment can help counter this. Most of the Clearfield® hybrid varieties provide rapid autumn growth and they are all tolerant to SU residues which can exist if the soil has not been properly cultivated after SU use in the previous crop.
Later drilled crops may also allow neighbouring trap crops of vosr to be more effective and have other agronomic benefits of lower risk of Verticillium, Club Root, TuYV and Light leaf Spot. Once you have a crop established, Clearfield® can help with other aspects of crop management.
The UK and EU legal limit for erucic acid (EA) will move from 5% to 2%. In 2018 20% of crops exceeded the 2% limit – these will now likely suffer deductions of £40/t, or worse, rejection.
The recent AHDB study has found that volunteers are the main source of EA contamination, with the high EA originating from previous HEAR cropping, or even the pre double-low days since the dominant EA gene persists through the generations. As you might expect, FSS crops are the worst – with 87% of the 15 FSS samples in the AHDB study exceeding the 2% level.
Removing volunteers removes the EA problem and it also means you really can use seed rate to achieve the optimum plant population!
Clearfield® herbicides also control brassica weeds which are another potential source of erucic acid.
There are 16 Clearfield® varieties available for autumn 2019 with a range of agronomic profiles to fit each situation. Over the years, the initial yield lag has been eroded. Real farm data provided by Clearfield® growers in 2017, covering 2,800ha, showed an average yield of 3.9t/ha, matching the national average. Remember that RL trials are performed on ‘perfect’ sites, not challenged by weeds or possible SU residues. Talk to the individual breeders about their Clearfield® varieties
