Cold spell reduces aphid risk for British potatoes
Seed potato crops could face a relatively low virus risk from aphids this year as forecasts suggest they will be appearing late and in low numbers. Potato aphids are two weeks later than last year because of the cold weather. The Rothamsted Insect Survey showed that the first potato aphid suction trap captures are expected to fall during the second week of June.
Potato aphids are two weeks later than last year because of the cold weather. The Rothamsted Insect Survey showed that the first potato aphid suction trap captures are expected to fall during the second week of June
Rothamsted's Dr Richard Harrington said: "Due to the exceptionally cold winter, these first flight predictions are more than 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."
Harrington added that this was the case for most of the aphids affecting potato and vegetable crops - apart from species such as the willow carrot aphid that are not as affected by cold winters.
Planting of potatoes has largely been on time with some three quarters of the British crop going into the ground by the end of April. This means that Scottish crops emerging now could be free of peach-potato aphid pressure for four to five weeks. English crops could have a shorter but still welcome respite of one to two weeks.
However, Science & Advice for Scottish Agriculture's (SASA) Dr Jon Pickup stressed that growers of Potato Virus A(PVA) and Potato Virus Y(PVY) susceptible varieties will still need to take account of non-colonising aphids that could transmit these non-persistent viruses before peach-potato aphids arrive.
Pickup said: "In a potentially late aphid year like this, monitoring is more important than ever. Keep a close watch on the Rothamsted/SASA aphid bulletins and the Potato Council/Central Science Laboratory aphid monitoring website to inform decision making. As always, the need for thorough early 'rogueing' of all seed crops cannot be over-stated."
Bayer CropScience's Dr Bill Lankford added that the implications of this year's late and low forecasts were that PVAand PVY-susceptible varieties may only need pyrethroid or pirimicarb sprays until peach-potato aphids arrive.
Growers of non-susceptible varieties should discuss when to start programmes and whether they can get away with fewer sprays with their agronomists.