Growers advised to take action now as aphids arrive early again

Some aphid species have appeared a month earlier than forecast and whitefly have already been spotted on overwintered brassica crops, an agronomist has warned growers.

Untreated sprouts contaminated by whitefly - image: HW
Untreated sprouts contaminated by whitefly - image: HW

The situation is similar to this time last year when agronomists saw infections begin from late May- early June.

Last summer, as in 2009, whitefly numbers reached epidemic levels in Lincolnshire.

UAP agronomist Dan Hayes said: "It’s a clear sign this year’s crops could again be at risk of early infestation."

The Rothamsted Insect Survey has already recorded first catches of peach–potato aphids at the Starcross, Wye, Silwood Park, Broom’s Barn and Writtle trap sites – and Hayes has found the first in Lincolnshire crops.

He said: "These are a month earlier than forecast so the effects of the cold winter may have been outweighed by the warm dry spring."

Where crops face pressure from either or both of these sucking pests he advises control programmes based on Movento (spirotetramat).

"Timing is key though and you need to deploy the two permitted sprays for best effect according to the main target."

To control whitefly Hayes uses the first spray during early infestation to target the larvae.

Under sustained pressure he follows with Biscaya (thiacloprid), for further suppression and resistance management, and holds the second spray back until late August to early September to maximise protection of harvestable produce.

If control has to begin in June he advises adding a Plenum (pymetrozine) spray between Biscaya and the second Movento.

Should the main target be aphids – particularly mealy cabbage aphid –  a subtly different approach is needed.

"Early on when the crop canopy is more open they can be reached with other chemistry such as Biscaya. It’s therefore best to keep the first Movento spray until mid season when the crop has thickened up and you need to start protecting harvestable parts."


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