THE FORECAST for potato aphids is predicting them to be late and in low numbers, which suggests that most seed potato crops could face a relatively low virus risk this year.

The Rothamsted Insect Survey’s potato aphid forecast, so far says it looks unlikely that peach-potato aphids will fly in Scotland before July. Predictions of first capture in suction traps are July 8, at Dundee and July 13 at Gogarbank, near Edinburgh.

For England, it’s slightly different, but with a huge range – from May 24 at Writtle to July 16, at Newcastle, but most fall in the second week of June.

Rothamsted’s Dr Richard Harrington told The SF this week: “Due to exceptionally cold winter, these first flight predictions are two weeks later than last year’s and about a month later than average. Potato aphid numbers are also expected to be much lower than average during the critical part of the growing season when potatoes are especially susceptible to viruses.”

Planting, though, has largely been on time, with approximately three-quarters of the GB crop in the ground by the end of April. If the predictions hold true, Scottish crops emerging at the end of May to early June could have a welcome four to five weeks free of peach–potato aphid pressure.

However, Science and Advice for Scottish Agriculture’s Dr Jon Pickup, says that growers of PVA and PVY susceptible varieties will still need to take account of non-colonising aphids, particularly cereal aphids that could transmit these non-persistent viruses before peach–potato aphids arrive.

Bayer CropScience’s Dr Bill Lankford says the implications of this year’s ‘late and low’ forecasts are that PVA and PVY susceptible varieties may only need pyrethroid and/or pirimicarb sprays until peach-potato aphids arrive. Growers should discuss with their agronomists when to start programmes and whether this means they can get away with fewer sprays.