Treatments keep yellows at bay
Treatments keep yellows at bay
VIRUS yellows in sugar beet is unlikely to be a big problem this season despite the mild winter, thanks to widespread use of aphicide seed treatment. But longer term implications could be on the cards.
With few frosts since the New Year and only one below the minus 7C (19F) needed to kill aphids the prognosis seems bad at first sight, says IACR-Brooms Barn entomologist Alan Dewar.
Virus-bearing aphids could be flying by May 2, three weeks earlier than average, and computer predictions suggest up to 88% of untreated plants from Lincs northwards could be infected with the disease in August.
However, with 70% of the crop due to be sown with Gaucho (imidacloprid) treated seed and 10-12% more likely to receive aphicide granules such as Temik (aldicarb), the true outcome is expected to be closer to last Augusts 1.6% national average.
"Such is the extent of crop protection at drilling these days that even untreated crops are likely to remain relatively uninfected because the aphids will have a job to find them," says Dr Dewar.
However, extensive use of imidacloprid in sugar beet and increasingly in cereals (as Secur) could have other consequences, he admits. It could select for resistant aphids and soil microbes which break the insecticide down faster.
There are no signs of either yet, he says. "But there is evidence for both processes occurring in other insecticides." Where carbofuran (as in Yaltox) is used frequently in carrot growing soils, for example, it suffers enhanced degradation.
Beet virus yellows
* Mild winter & few frosts.
* Potentially high disease risk.
* About 80% of crop protected.
* No evidence of resistance yet.
BEETVIRUSYELLOWS
• Mild winter & few frosts.
• Potentially high disease risk.
• About 80% of crop protected.
• No evidence of resistance yet.