Clothianidin may see end to follow-up BYDV sprays

Insecticidal seed treatments based on the new active ingredient clothianidin could make the need for follow up barley yellow dwarf virus pyrethroid sprays obsolete in all but the most high pressure situations.

The claim, made by respected ADAS entomologist Jon Oakley, is a direct result of the eight weeks’ protection the new Bayer CropScience Deter range of insecticidal seed treatments gives against BYDV-carrying aphids.

Three Deter products should be fully launched into the market next autumn – Redigo Deter for wheat; a Raxil-branded product for barley, which is awaiting full approval; plus straight Deter for use as a co-application product.

It follows the successful introduction of the standard seed treatments Redigo, Redigo Twin and Raxil Pro in the current season, Bayer CropScience seed treatment campaign manager Adrian Cottey says.

“We’re at the halfway stage in a huge change in seed treatments for UK farmers.”

Deter is a significant advance on the Secur range growers will be familiar with, he says.

“In trials gram for gram it is more effective than imidacloprid.”

A better overall profile has also allowed Bayer to register Deter at a higher dose than Secur – 50g/100kg seed compared with 35g/100kg.

“It means we can deliver significantly more of a significantly more active insecticide, and it has a real impact on what Deter can do.”

Top of the list is controlling autumn aphids that transmit BYDV.

“Deter will last for two weeks longer than Secur.

In many parts of the country it will take away the risk of BYDV for mid-September sown crops, so they won’t need any follow-up.”

Crops sown earlier or in high risk areas may potentially still need a follow-up, he believes, but Mr Oakley is more bold in his assessment.

“If you use a seed treatment you won’t need to worry whether to spray or not in all but the most exceptional circumstances.”

In TAG trials substantial yield increases have been seen with either Deter seed treatments or pyrethroid foliar sprays, but no further increase was seen by applying both, TAG regional agronomist Ben Freer reports.

Even so, for some farmers deciding not to overspray will be an act of faith, he recognises.

“It comes down to whether you are brave enough.”

But it could bring some big advantages, not least because growers won’t have to compromise on BYDV spray timing, as happened this year (see panel), because they are waiting for the correct timing for grassweed herbicides, in particular Atlantis (mesosulfuron-methyl + iodosulfuron-methyl-sodium).

Logistically, using a seed treatment could really help, Mr Freer adds.

“Farmers’ management time is stretched, so it depends on his preference; will he invest upfront or be prepared to do a separate BYDV application in the autumn?

“Investing in a seed treatment could be particularly useful for early drilled crops, which will need spraying when he is still trying to establish other crops.”

As well as early drilled crops, where Deter’s activity against gout fly could prove useful, the product could also be used on crops with a more conventional drilling date, where Deter’s slug activity will be beneficial, Mr Cottey suggests.

Deter is the first seed treatment to have a label claim for slug activity.

“We have got consistent data proving it reduces the amount of grain hollowing caused by slugs.”

Activity is easily at the level of a pre-emergence or admixed slug pellet treatment, he says.

“But it doesn’t protect foliage, so you may need to follow up if there is leaf shredding pressure.”

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