Continued hot weather means cereal crops face a high risk of BYDV infection this season.
Last year saw the worst incidence for more than 50 years in many areas, to leave a legacy of inoculum now being spread by aphids, according to Syngenta.
The company’s insecticide specialist, Max Newbert, says: “Warm conditions increase the numbers and movement of aphids, but also shorten the persistency of any seed treatment.
“Growers should be ready to tackle rising aphid numbers as soon as possible, to prevent early BYDV infection.
“Earlier infection will result in more severe yield effects and increases the risk of secondary spread from initial hot-spot foci through the season. Early sown crops are most at risk, however, delayed drilling - to aid blackgrass control - means crops will be slower to develop and remain at more susceptible early growth stages for longer.”
Bird cherry oat aphid and grain aphid are the primary vectors, says Mr Newbert. “Fast knock-down of aphids is important to stop feeding activity and prevent further virus spread.
“The UV stability of Hallmark Zeon, provided by its titanium dioxide formulation, is especially valuable to maintain better persistence and effective results in bright, sunny autumn conditions.”
He advises that the product should be used at the full rate of 50 ml/ha. “Field trials and lab research indicates grain aphid with KDR resistance remain susceptible to full rate treatment; whilst reduced rate applications achieved a lower level of kill and increased risk of resistance developing. Independent resistance monitoring has shown no pyrethroid resistance among populations of bird cherry oat aphid.”