The number of beneficial insects seen in the south east of England this year has resulted in vegetable growers experiencing a ‘mid-season crash’ in the number of aphids appearing in their crops, according to an industry expert, who predicted that this situation will soon be repeated in other areas.

However growers are also being warned to think carefully about their strategy for further pest control if damage to the beneficial population is to be avoided.

UAP’s Chris Wallwork explained: “Levels of beneficials are high because of the high population of aphids found earlier in trees, shrubs and other wild species. This has provided a good feeding station for beneficials such as ladybirds - they don’t mind if they find aphids in a crop or in a tree.”

Wallwork pointed out that it was ususal for the mid-season crash to start in the south east before moving north, though he stressed that not all aphid numbers have crashed so far, with black bean aphids hanging on for another week or two after others have disappeared.

Wallwork went on to say that caterpillars are late in arriving this season, with those going into last year getting targeted by large numbers of parasitic wasps. “The slow start to caterpillars and late arrival of migrants has tied in very nicely this year to give growers the opportunity to deal with caterpillars while looking after the parasites at the same time.”

He advocated that instead of using broad-spectrum pyrethroids for control of caterpillars, which risks killing parasites, growers now have the opportunity of using new chemistry in the form of Steward (indoxacarb) for control of caterpillars. “This will kill all moth and butterfly caterpillars but be safe to beneficials,” he says.

“Most aphids in the UK are controlled by beneficials, not sprays, and so it’s important that within a crop we look after beneficials with better targeting of applications. The beneficials are, after all, providing pest control for free.”