Cut down recovery for OSR
Oilseed rape crops that were mown down or grazed off over the winter, in an effort to remove high populations of cabbage stem flea beetle larvae in leaf petioles, appear to have recovered remarkably well.
On the iOSR Focus Site in Suffolk, Syngenta Field Technical Manager, Georgina Wood, reported virtually no losses in plant numbers from one or two passes with the mower, with good levels of initial regrowth triggered by early spring conditions.
And in Norfolk, where iOSR grower, Chris Eglington, had grazed sheep for six days across half a field in January, recovery was remarkably strong. By early April, with the grazed portion at early stem extension, it was still significantly behind the ungrazed crop – where some plants were just breaking into flower. However, the crop was extremely consistent and vigorous.
Chris Eglington's grazed OSR crop recovery at the beginning of April (above, left) compared to pictured on 17 February, below.
The result in terms of CSFB larvae present, and the resulting yield, could prove one of the most enlightening advances in managing a pest that threatens future viability of OSR cropping for many growers.
Larvae on the move
Cabbage stem flea beetle continue to be a major concern for iOSR growers. In Cambridgeshire, Ian Lutey reported infestations of up to 25 larvae per plant had stunted growth of some plants, leading to risk of an extended flowering period with the mixed growth stages.
With the main stems still appearing relatively unscathed by larvae damage, even on the stunted plants, he’s hoping hybrid varieties can still compensate and put on sufficient growth to yield well.
The high level of larvae damage is not only likely to directly affect yield, but the variable growth stages as plants seek to recover can be expected to result in a protracted flowering period.
Protecting against exposure to sclerotinia and prolonging available green leaf area retention for longer is going to be crucial for crops to fill remaining pods.
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