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

Shelter

Hedgerows

Hedgerows, with year-round shelter, provide the largest source of beneficials. Over 1,500 insect species have been found in them. Hedgerows provide alternative prey as well as pollen and nectar.

Beneficial populations fall after hedge cutting. Therefore, do not cut hedges every year to a standard height as this produces excessive scar tissue and few healthy shoots. It is best to cut different hedges at the end of winter in different years, ideally on a two or three year cycle.

To maintain insect diversity, manage hedges to create different structures with varied plant species. New hedge plantings should include a diversity of species. When gapping up, or planting new woodland, select species that support most invertebrates.


Well-managed hedgerow – flower-rich at base

Flowering shrubs and herbaceous plants, along the hedge base, are a rich source of pollen and nectar; nettles support a diversity of prey. Re-sow degraded hedge bases covered in noxious weeds, eg ragwort, thistles and sterile brome, with a flower-rich grass mix.

Tussocky grasses, along hedge bases and fence lines, are particularly important for overwintering beetles and spiders. Protect this habitat from insecticide and herbicide drift.


Tussocky grass along hedge base

All national agri-environment schemes have options for hedgerow management.

Insect and mite numbers associated with some common hedgerow and woodland plants

Plant species Number of insect and mite species
Willow species 450
Oak 423
Birch 334
Bramble 240
Hawthorn 149
Blackthorn 109
Beech 98
Poplar species 97
Crab apple 93
Alder 90
Elm 82
Hazel 73
Field maple 51
Ash 41
Lime 31
Hornbeam 28
Rowan 28
Sycamore 15
Holly 10
Sweet chestnut 5
Horse chestnut 4

Source: Kennedy and Southwood (1984)

Managing uncultivated areas

Many ELS and OELS options do not permit cultivation. The aim is to protect ground vegetation associated with particular landscape features, including hedgerows, buffer strips, ditches, in-field trees and archaeological sites. Such areas can provide shelter for a diversity of beneficials. They have added value for pest control if flower-rich.

Grass margins and buffer zones

Grasses support a range of insects that can help maintain beneficials through the winter. Undisturbed ground under grasses suits species that overwinter in the soil. In summer, these habitats offer a refuge from disturbance and alternative foraging areas.

Tussocky grasses support large numbers (over 3,000/m2) of overwintering beetles and spiders.

 
Grass margin

Beetle banks, formed by ploughing two furrows together to form a raised bank, create drier conditions favoured by insects. Beetle banks can be located to divide large fields. This reduces the distance over which beetles must disperse in spring, ensuring rapid, even coverage across the field.


Grassy strips, associated with post and wire fences, support high densities of beneficials

Ditch and dyke banks should be cut in alternate years, so that some well-grown habitat remains. Maintain shallow, sloping banks and avoid cutting ditch margins

Beetle bank

Only mow during the first year to aid establishment.

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