9 February 1996

Yellows risk is low

DESPITE mild weather in the New Year, subsequent frosts have been enough for Brooms Barn to issue a forecast for generally low virus yellows risk to this years sugar beet crop.

Although there were only 11 ground frosts recorded in January, some were of aphid killing proportions (less than -7C). "It is still too early to make a final forecast for virus yellows incidence in August," says Brooms Barn entomologist Dr Alan Dewar.

But if February brings an average 14 frosts, which is most likely, virus yellows will hit 10.4% of plants in the eastern region, 11.6% in the north and 5.8% in the west, he predicts.

As more than half the crop will be treated with Gaucho (imidacloprid), it is only the remaining 47% that may need protecting.

"If these conditions keep up, aphicidal granules will only need to be used in the highest risk areas. This year that means Lincolnshire, and anywhere near fodder beet clamps which will not be used up by the time the new crop emerges. Elsewhere, sprays, when necessary, should be the preferred option," he advises. &#42

Harsh frosts have hindered beet storage this winter, but the good news is that they could have cut the risk of virus yellows later this year.