Science into practice: Controlling flea beetles on leavy salad brassicas
by HDC
Horticulture Week
29 May 2009
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Even small numbers of adult flea beetles feeding on high-value speciality brassicas grown for salads can cause shot-holes in the leaves, which significantly reduces quality and thus marketability.

Control of this pest has been exacerbated by the withdrawal of key insecticides and by the increase in the acreage of rape, which acts as a reservoir for brassica pests.

HDC project FV 301 is investigating what control strategies growers can use in the future, combined with a better understanding of the life cycle of the flea beetle.

After two years, several chemical treatments have been identified as giving significant control, applied as sprays and one used as a seed treatment. They will be trialled again this summer, as flea beetle pressure was relatively low during the trial period in 2008, in order to confirm results with a more rigorous test.

The well-proven control technique of using nylon crop meshes, like Wondermesh and Enviromesh, as physical barriers provided the best protection in the first two years of trials. Insecticide-impregnated mesh provided the same level of protection as crops under standard mesh that had also been sprayed. However, pre-treated mesh would be more expensive, effective for only a year and personal protective equipment would need to be worn when handling it. The trial proved that the danger from flea beetles is not from those that hatch from underground under the mesh. None were detected. The immigration of adult beetles into the crop from surrounding rape and other brassica crops on surrounding farms or even grassland with wild and volunteer brassicas was by far the most important source of adults causing damage.

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