Myzus aphid explosion imminent

Nine Myzus persicae (peach-potato aphids) and 27 potato aphids were caught in Broom’s Barn water traps in the week 7-13 May, the research station’s Mark Stevens reports.

All of the Myzus were caught in the Bury and Wissington areas, with four of the nine Myzus trapped at Potton, Bedfordshire, a traditional hotspot because of the higher intensity of brassica crops in that area. “It would appear they have over-wintered and are now migrating out of brassica crops.”

The figure is way below the unprecedented 1654 Myzus aphids caught in the equivalent week last year.

But while the picture was not yet moving that quickly – a reflection of the cooler April weather – Dr Stevens warned an explosion in numbers was imminent. “We might not quite reach those [2007] high numbers, but everything is pointing to large numbers coming into crops by the end of the month.”

The first Myzus aphid caught a couple of weeks ago was positive for MACE resistance, he added. “That is a concern. If we have high MACE resistance and Kdr resistance, then the efficacy of the only two foliar chemicals (Aphox and Dovetail) that can be used in sugar beet could be compromised.”

That could be an issue for the 10% of growers who hadn’t used a neonicotinoid seed dressing, he said.

Beet that was protected with a seed treatment should not need to treat again, he said. “Even those who planted in late February/early March should be OK for another five or six weeks, and, hopefully, the crop should be past the 12-leaf stage when adult plant resistance kicks in by then.”