Beetle banks can boost predatory insect numbers which help control pests.
Beetle banks are grass mounds, about 2 metres wide, which run through the middle of large arable fields.
These banks are generally appropriate for fields larger than 0.2 square kilometres – fields larger than 0.3 square kilometres may warrant more than one beetle bank.
- Beetle banks can boost predatory insect numbers which help pest control.
- The field headland can remain intact so the whole field is still farmed as one unit.
- Benefits can be boosted by measures to protect the banks from pesticide sprays.
Benefits to wildlife
Beetle banks boost numbers of beneficial insects and spiders on arable farmland
A tussocky grass strip through the middle of a field, such as a beetle bank, provides essential over-wintering habitat for many welcome insects and spiders. These move into the crop in the spring and feed on crop pests.
These species can travel up to 250 metres from grass field margins during spring, so they do not reach the centre of large fields.
Beetle banks provide an over-wintering habitat that enables such predatory insects to cover a whole field.
Beetle banks provide habitat for ground-nesting birds and small mammals
Beetle banks also provide habitat for species which prefer to nest in open farmland away from field boundaries, such as corn buntings, reed buntings, skylarks and mammals like harvest mice. Grey partridges sometimes choose them in preference to hedge banks to avoid predators.
How to create a beetle bank
September is the best month to establish the grass sward which forms a beetle bank.
You will need to:
- Plough furrows that point towards each other from either side during cultivation of the field to create a raised bank of about 0.4 metres along the plough line. (The headland at each end of the beetle bank can remain cropped.)
- Ensure the grass mix includes a high percentage of tussock-forming species such as cocksfoot or timothy grass. The rest of the mix can consist of fescues and bents. All species should be of native origin.
- Broadcast the seed immediately after the cultivation to get good establishment.
- Three cuts may be necessary in the first summer, when the sward reaches 10 cm in height. This encourages the grasses to tiller and helps control invasive annual weeds.
- Once established, you should only cut the grass strips in order to get the dead tussocks to regenerate. This is likely to be no more than once every three years.
Protection from sprays
Beetle banks are particularly vulnerable to the effects of pesticide drift because these narrow strips of grass are sprayed on either side.
On light soils with a low weed burden, conservation headland management on either side of a beetle bank will enhance its value for insects and birds whenever the adjacent crop is a cereal.
Conservation headlands are selectively sprayed margins. You should avoid the application of insecticides within at least 6 metres of the beetle bank whenever possible, as these will be particularly harmful.