OSR pod sealants offer significant return on investment – Agronomist & Arable Farmer – James Boswell

Selecting an appropriate variety is key says Mr Boswell, and in Kent popular conventional varieties Compass and Elgar both provide impressive gross output and oil content scores, good resistance to lodging, stem stiffness and autumn vigour. But, neither of them are shatter proof.

“Pod sealants should be applied in a separate pass up to 12 days before applications of glyphosate to burn off the crop prior to harvest,” he says. “Applying glyphosate before the pod sealant or at the same time, can result in significant mechanical related seed loss.”

Tramline seed losses, in particular, can be as high as 35%, he points out. Also we are more conscious of using insecticides at flowering so there is likely to be damage from seed weevil and bladder pod midge, which are both responsible for splitting of the pods.

“OSR acreage is down locally by about 25-30% this year and, going forward, is likely to continue falling until reliable control of cabbage stem flea beetle can be achieved,” says Mr Boswell. In general, autumn rape crops established well in Kent, he says, and grew away from flea beetle so potentially yields could be higher than in a season where flea beetle did take hold, keeping that extra seed in the pods is critical. Justification for using pod sealants is even greater where OSR crops were not drilled until later and therefore more likely to have been affected by flea beetle.

“In February we did find some evidence of flea beetle stem damage in crops and these should be treated with a pod sealant,” he advises. “Apply Zip-Pod when seed pods are more malleable – green and bendy – which is around GS 80-82, in a separate pass at a rate of 1.0l/ha in a maximum 150l/ha of water. Afterwards, the tank must be cleaned out with the adjuvant Activator-90.”

OSR growers could learn lessons from last autumn, says Mr Boswell. “Remove straw from the previous crop, drill early and apply a DAP starter fertilise,” he adds. “Rolling fields after drilling will also help seed-to-soil contact of the new crop and reduce slug movement channels and drill early into moisture. If there is no moisture and the forecast is dry, then avoid drilling.

“Margin over input cost for a pod sealant is about 1:12 so it will be very prudent to apply as soon as label recommendations indicate. Growers only need to lose about 30-40kg/ha of seeds to pay for the pod sealant so it makes sense to always apply one.”

He adds that just by selecting shatter proof varieties does not mean that crops are protected. “If pod midge is in the crop already then loss of seed is more likely to occur. Effectively what happens is seed weevils bore a hole in the pod, which is then impregnated with the egg of a pod midge. Seed weevil can damage around 20% of pods and reduce yields by 5%. Pod shatter from seed weevil can be confused with bird damage,” Mr Boswell says. “So, if you apply a pod sealant on all crops, growers are at least adding some level of protection to the pod. Also, seed crops cannot be sprayed with glyphosate so a pod sealant becomes more essential.”