Adult pollen beetles (Brassicogethes spp.) are occasional pests of cauliflower and broccoli. The adult beetles feed on the curds or florets causing physical damage. This type of damage usually occurs in mid-summer when new adults emerge from oil seed rape crops and move into other areas to feed. They are also often found in flowers at this time. These new adults feed for a period of time and then seek hibernation sites, for example in leaf litter at the base of hedges. They overwinter as adults and emerge from hibernation in spring, when they can again be seen feeding on flowers such as dandelions. They then move to suitable host plants such as oil seed rape to lay eggs. Once hatched, the larvae feed on flower buds and then drop to the soil to pupate, from which the new generation of adults emerges.

The pollen beetle forecast indicates the predicted dates of the migration of newly-emerged pollen beetle adults from oil seed rape fields to feeding sites – such as broccoli and cauliflower crops. This usually happens towards the end of June.

The risk of infestation is obviously higher if horticultural crops are close to fields of oil seed rape. Pollen beetles are particularly active when the weather is warm and humid. Adult pollen beetles will continue to feed for a period of time and then seek hibernation sites, for example in leaf litter at the base of hedges.

Updated 12 July