Science Into Practice - Better control of whitefly in Brassicas

Whitefly is becoming increasingly difficult to control, on kale and Brussels sprout in particular. It is not clear why this is the case, although outbreaks appear to be more severe in hot, dry years (2003, 2006, 2010).

There are a number of possible insecticide treatments to control whitefly, but we do not have a clear understanding of a good spray treatment programme and the optimum timing of sprays.

There are also questions about the best ways to apply spray treatments to maximise control and the best way to space crops to ensure effective distribution of insecticides applied as sprays.

Natural enemies such as ladybirds or parasitic wasps may be suppressing whitefly infestations, but the extent of this is also unknown. If pyrethroid insecticides are applied to Brassica crops to control caterpillars and other pests, then these will kill the natural enemies. If whiteflies are resistant to pyrethroids, the applications may exacerbate the problem.

The FV 399 project being carried out by Rosemary Collier of Warwick Crop Centre, University of Warwick, was requested by the Brassica Growers Association in anticipation of a 'bad' whitefly year in 2011. The project is evaluating the effect of spray programmes using approved and promising novel insecticides for the control of whitefly. The work will also look to identify the best spray application system by examining the deposition patterns, and investigate the susceptibility of different whitefly life stages to insecticides in potted plant tests.

Date for your diary

HDC/NIAB drilled onion produce demonstration, Cambridge, 8 November.

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