Cambridge, United Kingdom
27th May 2014
This spring’s first flights of peach–potato aphids have been two to four weeks earlier than average setting the scene for a summer of potentially high numbers in vegetable brassica crops.
The Rothamsted Insect Survey (RIS) forecast of first catch at the Kirton trap in the heart of Lincolnshire’s brassica growing area was 27th April, almost three weeks earlier than the previous ten years’ average (16th May). The first peach–potato aphid was actually caught there on 17th March but this was something of an anomaly according to the Allium & Brassica Centre’s Andy Richardson.
“It usually takes a fortnight or so from the first suction trap catch until we see aphids in crops. This year that was during the second week of May: a month earlier than average.” First catches across the RIS network of suction traps in England have generally been two to four weeks earlier than average – as expected – and it is looking like the end of May first flights forecast for Newcastle, Edinburgh and Dundee will not be far out.
Years of early first flight often develop into years of high numbers as aphids are able to multiply through more generations and the dry, warm conditions that favour aphid multiplication are equally conducive to whitefly. Andy Richardson is therefore readying growers to tackle significant infestations of both pests this summer.
“Robust programmes will need to be built around use of the insecticide Movento (spirotetramat) which controls all stages in the generation of aphids and whitefly and inhibits their ability to produce offspring, effectively breaking the life cycle and stopping the next generation,“ he advises.
“Its two way systemicity gets to grips with aphids hiding under lower leaves, getting to the parts other insecticides struggle to reach. This means it has to be applied when plants are actively growing and pests are actively feeding which generally means up to the end of September. Using Biscaya (thiacloprid) between the two permitted Movento applications will provide further suppression and be complimentary for resistance management.”
Andy plans to commence this ‘sandwich’ programme as pest numbers build up, which he expects will be in late June. Should further migration occur beyond the second Movento spray he will deploy a second Biscaya. “This approach will achieve the best possible control of aphids and whitefly and safeguard harvestable quality into Autumn,“ he concludes.
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