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Morton’s Fork

Date Added: 17/05/2016

Blog: By Richard Elsdon, Technical Consultant, United Oilseeds

One of the very few pieces of historical knowledge I was able to retain whilst at school was the philosophy of Bishop John Morton of Canterbury (1420-1500). He was an interesting character who supported the Lancastrians during the Wars of the Roses (ie the losing team) but still managed to be given ambassadorial roles and become the Bishop of Ely. Then Richard lll became King and once again Morton was on the wrong side, eventually fleeing to Flanders.

Then when Henry Vll became King in 1485, Morton returned and became Archbishop of Canterbury and then Lord Chancellor. It must have been about this time that his infamous money-grabbing taxation policy was formed. Essentially he believed that the rich could afford to pay taxes and, at the same time, so could the poor as they were saving all their money and actively choosing to live in squalor!

I remember this historical quirk when looking at flowering crops of oilseed rape at this time of year looking for adult seed weevil. These weevils have two fork-shaped antennae which are bent about half way down their length, hence my thought about Morton. Now back to the weevil which lays a single egg in the developing pod of the oilseed rape. This egg hatches into a larva which in the course of its development can eat up to a quarter of the developing seeds. However, there is worse to come. The larva chews a hole in the side of the pod and makes its exit to pupate in the soil.

It is this exit hole which allows the female bladder pod midge to insert a multitude of eggs into the damaged pod. These then hatch into larva which, by the action of their grazing, cause the pod to bulge (hence the term bladder pod midge) and often split, losing any remaining seed on to the ground.

Control of this horror story entirely depends on a nicely timed application of approved insecticide to control the female seed weevil. Control is only required if one weevil per plant can be found when the crop is in flower or an average of half a weevil per plant in the North.

The story doesn’t end here. We know that some fungicides when mixed with synthetic pyrethroids can produce a highly toxic mixture, which will have an adverse effect on bees. This is definitely something to discuss with your agronomist to ensure that any tank mixes you use are not toxic to bees.

Having just updated the estimated gross margins for harvest 2016, I can now report that with today’s prices, and applying average premiums, your crop could be worth a total of £300 per tonne at harvest time before bonuses.  At this value,  it is worth checking to see what insect activity is occurring and then taking the appropriate action.

John Morton was an unashamed opportunist who worked the system of the Middle Ages to his advantage. It is up to all of us to use our knowledge of the oilseed crop to ensure that these latter day versions of Morton’s fork do not leave us out of pocket.

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