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The Lesson of Devon Loch

Date Added: 17/05/2017

BLOG: By Richard Elsdon Technical Consultant, United Oilseeds

 Way back in the mists of time, 1956 to be exact, the Queen Mother’s horse, Devon Loch, took part in the Grand National. The horse had won twice that year and had run well at Cheltenham, but was not especially fancied to win. However, during the race, both the Favourite and a previous winner fell at the first fence, removing at one fell swoop two of the most fancied horses.  During the rest of the race, Devon Loch’s progress was steady. He managed to clear all of the jumps and, perhaps most importantly, avoid horses falling in front of him.

His jockey that day, Dick Francis, said later that the horse had a lot left in him as they turned into ithe final straight and that the result should have not been in any doubt. But disaster struck about 50 yards from the finish when, for no apparent reason, Devon Loch appeared to jump in the air and land on his stomach. He was consequently unable to carry on to claim victory.

You can see the race  on you tube

Oilseed rape is now at the stage when for many crops the risk of Sclerotinia infection has lessened as flowering has passed its peak. Some growers may be tempted to be considering applying a little extra nitrogen to boost yield. My opinion is, after looking at many yield result, that this is rarely profitable. It may lead to a small increase in seed yield but will inevitably lead to a lowering of the oil content thus resulting in a break even situation (another example of the ‘busy fool’?).  In my view, growers need to continue to be vigilant because there is one more obstacle to be aware of before closing the gate. I am referring to the seed weevil (Ceutorhynchus assimilis).

The female weevil will only lay one egg in a pod. The larvae hatches and eats up to a quarter of the seeds in the pod before chewing an exit hole dropping to the ground and pupating. This loss of seed is bad enough. But there is worse to come. The female Bladder Pod Midge (Dasineura brassicae) is looking for a site in which to lay eggs. The exit hole left by the seed weevil larvae is a perfect entry point into the pod. In this case the female lays 20 or 30 eggs which then hatch into tiny larvae. These feed on the pod lining and in doing so, cause it to dry and distort often into a bladder shape. During this distorting the pod will split, allowing the larvae and any remaining seed to fall to the ground.

Control measures center round spraying the crop with an approved insecticide if the threshold of more than one weevil per plant in southern Britain - or an average of half a weevil in the north - has been exceeded. The decision to spray should only be taken after careful monitoring of the crop. Precautionary spraying could lead to accelerated insecticide resistance.

This decision is probably the last one to be made prior to the application of any pre harvest treatment. Spraying against the seed weevil has not generally been needed for a number of years but problems can arise when least expected.

We need to remember the 1956 Grand National and that a “sure thing” and “dead cert” are really no such thing.

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