Aphid alert as bugs survive mild winter

6 March 1998

Aphid alert as bugs survive mild winter

FARMERS everywhere are being urged to check crops for aphids after the exceptionally mild winter.

Met Office figures show January and February averaged 5.1 and 7.2C, compared with a more normal 3.8C. Ground frosts were also rare leaving plenty of aphids across the country. Recent cold weather may have halted some reproduction, but advisers still urge growers to check crops.

Scientists from IACR Roth-amsted, ADAS, SAC and CSL York first warned of a BYDV epidemic last October. The mild winter has vindicated their concerns.

In January aphids on unsprayed wheat numbered 500 per 12m (39ft) strip. By late February that had reached 700. "These numbers are quite amazing," says Adam Burgess of IACR Rothamsted. "Were even seeing typical BYDV symptoms now. Usually they dont develop until April or May."

Jon Oakley of ADAS Bridgets urges growers to check crops. Spraying to reduce early spring virus spread may pay, he suggests.

Further north another BYDV vector, the grain aphid, is causing considerable concern. All untreated winter barley in the west of Scotland, and half those in the east, have retained an overwintering aphid population, says Garth Foster of SAC Auchincruive.

Peach-potato aphids have survived well on oilseed rape and brassicas across the country and now threaten beet and potatoes. The first winged migrants are forecast to arrive in crops on St Georges Day, Apr 23, four weeks earlier than last year and the second earliest on record.

That could mean August virus yellows levels of 82, 98 and 56% in untreated beet in the east, north and west, reports Dr Alan Dewar of IACR Brooms Barn.

Aphicidal granules at drilling will probably pay if Gaucho-treated seed is not used in the east and north, notes Dr Dewar.

In Scotland, Dr Andrew Evans at the Edinburgh School of Agriculture says there is a higher potential for seed potato crops to be at risk. &#42

Peter McGrath

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