Mild weather prompts high risk of aphid attack

Higher than average aphid numbers and very mild weather are creating a greater risk of BYDV this year, researchers and agronomists predict.

According to the latest results from the Rothamsted Insect Survey, the number of potential virus-carrying aphids is slightly higher than the 10-year average.

That alone needn’t be a particular cause for concern, says Richard Harrington of Rothamsted Research.

“It’s just that we’re also experiencing some warm weather, which allows the aphids to move easily between the plants and spread the virus.”

The survey suggests virtually all areas of the UK are under threat.

“In the south and south west, the two aphids responsible for spreading BYDV are being found readily,” reports Dr Harrington.

The east of England is another hotspot, but all areas should be vigilant.

“It’s been warm enough to put the north and Scotland on alert too.”

BYDV inputs may need to be higher this season, due to a greater amount of early drilling, believes Richard Overthrow of The Arable Group (TAG).

“There’s certainly been a lot of aphid activity,” he says.

“That may just be a function of the mild conditions, which makes them easier to find, but they are around.”

Crops need protecting from the day they emerge until early November, when the aphids usually stop flying, he advises.

“There aren’t really any parts in the UK which escape BYDV, although coastal areas are often the worst hit.”

Early protection against the virus-carrying aphids from insecticides such as the Secur range may now be running out of steam.

“Treated crops will still need a follow-up spray.

You can count on getting around six weeks’ protection from a seed treatment.”

Without a seed treatment, protection has to come from pyrethroid sprays, with products such as Hallmark Zeon and Sumi-Alpha.

“You may only get two weeks’ protection from a foliar spray,” notes Mr Overthrow.

“Some are more persistent than others, but it will all depend on when the crop was sown.”

Applying a pyrethroid at a cost of 2.50/ha will always be the cheapest form of control, he remarks.

“But going on twice in the early autumn doesn’t always tie in with herbicide programmes.

That’s become more of an issue since Atlantis arrived on the scene.”

In the future, seed treatments should be seen as a management tool, he suggests.

“They give you some flexibility at a very busy time of year.

And the new ones coming along appear to offer up to eight weeks’ protection, which may do away with the need to spray altogether.”

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