Whitefly

Key Points

• Cabbage whitefly is normally a localised pest of broccoli, Brussels sprouts and cabbage
• Quality of produce is adversely affected by secondary sooty mould infections
• Some control of Cabbage whitefly can be achieved with Dursban WG

Introduction

Whiteflies are more normally pests of glasshouse crops, but the Cabbage whitefly — Aleyrodes proletella — lives outdoors, attacking crops of broccoli, Brussels sprouts and cabbage. Feeding by the adults and larvae on the underside of leaves from June to late autumn causes white or yellow patches to develop. Honeydew excretions allow secondary infections of sooty moulds to develop, adversely affecting the appearance and quality of produce.

Biology

Yellow eggs are laid in circular groups on the underside of leaves. Within a few days the eggs turn black, before hatching in about nine days at temperatures of around 21°C. Light green, flat larvae are only active for a few days and then remain motionless until they reach maturity. Whiteflies pass through four life cycle stages before reaching adulthood. Adults are covered in a white, mealy wax and only grow to about 1mm in length. Feeding on plant sap is achieved via stylets, much the same as with aphids.

Product Choice

Where applications of Dursban* WG are made for control of aphids and caterpillars, some control of Cabbage whitefly will be achieved if they are present at the time of spraying.

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