Beneficials on farmland: identification and management guidelines (HGCA Summer 2008)

Flower-rich habitat

Pollen and nectar are important food for many beneficials. Nectar provides energy and nutrients essential for egg production and increases longevity of parasitic wasps and hoverflies. Parasitoids most readily obtain nectar from flowers with an open structure or nectaries on leaf petioles, and are often seen feeding on flowers of umbelliferous crops, eg cow parsley, hogweed and wild carrot. Flowers most utilised by hoverflies include yarrow, cow parsley, hogweed, white campion, common knapweed, rough hawkbit, field scabious, lady's bedstraw, bugle, self-heal and red clover.

Beneficials also feed on pollen and nectar from hedgerows, shrubs, herbaceous plants, broad-leaved weeds and flowering crops. These habitats may support other beneficials by providing a suitable habitat for foraging and overwintering. Other farmland wildlife - currently in decline - including bumble bees, butterflies and farmland birds also use these habitats.

Perennial habitats

Of the agri-environment options, pollen and nectar mixes, as well as ‘floristically enhanced’ grass margins, provide the most floral resources.

Pollen and nectar flower mixtures

These mixtures, typically comprising clovers, vetches, birdsfoot trefoil and sainfoin, provide plants preferred by bumble bees and butterflies. They may be established with or without grasses, although the greatest numbers of beneficials occur in mixtures without grasses.

Floristically enhanced grass margins

Grasses in such margins initially prevent invasion by annual weeds. Non-aggressive, fine-leaved grasses, eg common bentgrass, crested dogstail and sheep’s fescue, should be used. Proprietary pollen and nectar seed mixes contain many plants, eg birdsfoot trefoil, utilised by beneficials and species, that support insects. If an existing hedgerow base does not already contain many umbellifers, then add these and yarrow to the seed mix. To ensure an even spread of flower resources across the farm, establish flower-rich swards in fields where the hedge base contains few flowering plants. In large fields, a flower-rich sward next to a beetle bank ensures more even coverage of beneficials.

Annual habitats

Broad-leaved arable plants can provide significant amounts of pollen and nectar in uncropped, annually cultivated margins and fallows or beneath crops with low or no herbicide inputs, eg conservation headlands and extensively farmed crops. Annuals, eg phacelia, buckwheat, alyssum or coriander, improve biocontrol levels in adjacent crops. They may be sown as a component of wild bird cover to provide a suitable foraging habitat for farmland birds. Some principles on this page result from Project Report 356 (2004) Managing biodiversity in field margins to enhance integrated pest control in arable crops (3-D Farming Project).

Floristically enhanced grass margin

Pollen and nectar margin

Hoverfly on umbelliferous flower

Phacelia strip

Wild bird cover with flowering plants

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