Crop Watch: aphid numbers on the increase

Aphid numbers are building in both cereal and pulse crops and some may warrant control with an insecticide, report our Crop Watch agronomists this week.

David Martindale of Arable Alliance (Yorkshire) says aphid numbers have been increasing in peas, which required controlling with an insecticide.

“Keep monitoring crops as recent warm weather can soon allow aphid numbers to increase quickly above the 20% of plants infested threshold,” he advises.

Mr Martindale says although June rainfall improved crops, it may have arrived too late for winter barley.

Many barley crops have large levels of secondary growth so applying glyphosate pre-harvest may be necessary, he adds, but wide maturity variations in a field means getting the application timing right could prove tricky.

Oilseed rape and wheats generally look well on the heavier land, but wheat on lighter soils or late drilled after roots will struggle to produce good yields, he reckons.

Philip Vickers, of Farmacy (Lincolnshire), says spring barley crops that have not been treated with an insecticide recently are suffering from high aphid numbers. “These will be treated with pirimicarb or a pyrethroid within the next week,” he adds.

Spring beans will be receiving a final bruchid spray as they finish flowering. A pyrethroid and half-rate pirimicarb will be used as black bean aphids are increasing, he says. “This will be our third bruchid spray in some cases due to the protracted season.”

However, disease levels are still low in bean crops, says Mr Vickers, so a low rate triazole and chlorothalonil will be enough to keep the crop clean.

Early maturing oilseed rape varieties are nearing desiccation timing, he says. “After recent rains, crops picked up some late nitrogen and the pod filling period has, thankfully, been prolonged. All crops will be treated with glyphosate, unless they are for seed.”

With the current high value of seed, most treatments will include a pod sealant to reduce the risk of pod shatter and harvest as much seed as possible, he adds.

Swaran Bachoo, of Agrovista (Buckinghamshire), says June rainfall saved the day for most crops, especially oilseed rape which is “looking good and should yield well”.

However, he says Septoria tritici is starting to appear on the middle leaves of some crops and mildew is visible on many.

Poor blackgrass control is also apparent in many crops, he adds. “Weeds were tough at the time of spraying due to the dry weather, but resistance may slowly be creeping in.”

Dan Dines of Wessex Agronomy Services (Wiltshire) says June rainfall has improved wheat crops, but he fears most are too thin to produce top yields.

Late foliar nitrogen has been applied to milling wheats with reasonable yield potential. “Only time will tell if we were right,” he says.