Ground beetles are key predatory insects that help control pests and weeds in crop production systems.

There are some 350 different ground beetle species recorded in the UK – 30 of which are commonly found on farmland. 

The benefits for farmers are clear. Beetles not only act as natural predators of all invertebrate crop pests – including flea beetles, weevils aphids, and slugs – but also have a compelling ability to consume up to 4,000 weed seeds/sq m every day.

See also: Grower’s tips for introducing cornflower and marigold crops

Kelly Jowett, applied entomologist at Rothamsted Research, is working closely with UK farmers to increase ground beetle numbers on farm.

“We aim to encourage a range of different ground beetle species across different cropping areas as each species has specific tolerances and preferences, and therefore a variation in benefits to farmers,” she says.

Dr Jowett explains what steps can be taken to improve populations.

1. Minimise tillage

Reduce the frequency of soil passes and level of soil disturbance, where possible.

As beetles lay their eggs in the soil, intense cultivations can negatively impact the number of eggs that hatch and larvae, which develop into fully grown adults.

Reducing cultivations therefore has a positive impact on their growth and development.

2. Intercropping and undersowing

Integrating a diverse and complex range of species into existing cropping systems can provide a greater range of habitats for beetles to support population growth.

3. Grass margins

The establishment of grass margins on the outskirts of fields can help provide a permanent habitat for beetles to overwinter in.

Tussock-forming grasses with mounds provide an effective overwinter permanent landscape feature.

However, in-field measures such as cultivations and undersowing may provide a greater effect on predation in crops than outer-field measures.

4. Monitoring and trapping

Monitoring and trapping ground beetles can be an effective way to track any potential baseline improvements that you have made on farm.

One simple method for catching ground beetles is to set up a pitfall trap.

Wheat pitfall trap © Kelly Jowett

This involves digging a hole about the same height as a 500ml plastic cup, ensuring the edge of the cup is level with the soil.

“These are ground-running beetles and we want them to run along the soil surface and fall into the trap.

“Making sure there is no lip to the cup that they can get trapped against or run around is key to effective trapping,” she says.

Unfortunately, during the sampling process the beetles are killed.

This is because ground beetles are predatory insects and will otherwise eat each other in the trap, providing an inaccurate representation of the number and species present.

On average, pitfall traps should be placed for between seven and 14 days, during which time anywhere between 20 and 100 beetles can be trapped depending on location, soil type and cultivation strategy.

Pilot trapping scheme and app launch

Dr Kelly Jowett © Kelly Jowett

Dr Jowett is working with 18 farmers and agronomists to pilot a farmer monitoring scheme.

Since mid-September, those involved with the scheme have been pitfall trapping to monitor the number and species of ground beetles, and helping to develop a quick and easy protocol.

The full monitoring scheme will be running next spring, which includes a farmland carabid ID guide, and an app to help growers map out and locate field traps and identify key beneficial species.