Getting the Best Out of CIPM3 / IPM3 Companion Cropping

Companion cropping - with its potential to support integrated pest management, improve soil resilience and diversify rotations - offers both opportunity and complexity. To succeed, the timing, species selection and management must be right. Go too late, sow the wrong mix, or let competition get out of hand, and the benefits may never materialise.

Managed well, companion crops can support pest control, improve soil resilience and make your IPM plan work harder

This "mini-guide" explores companion strategies for oilseed rape (OSR), sugar beet, cereals and other crops under the CIPM3 and IPM3 SFI actions, references relevant trials, and explains how companion cropping differs (or not!) from bi-cropping, intercropping and living mulches.

How companion cropping supports OSR establishment

Companion cropping is widely adopted by growers to mitigate cabbage stem flea beetle (CSFB) damage in oilseed rape (OSR)

We all know how OSR is highly vulnerable to CSFB damage. Companion cropping with the right mix of species is one of a set of risk management tools proven to be worth deploying, alongside other cultural controls such as variety selection, seed rate, moisture management, drill date and sensitive cultivations.

How can companion crops help mitigate CSFB damage?

Extensive trials (for example, the EU-funded EcoStack project) suggest that companions help OSR establish by helping to reduce the impact of pigeon and CSFB Autumn leaf feeding damage, and may reduce larval infestation later in the season. Depending on the species mix, companion crops can offer a masking canopy, scent that disguises OSR's natural volatiles and flowers which encourage natural enemies of CSFB, like parasitic wasps such as Microctonus brassicae and Tersilochus microgaster, into the crop.

What else do companion crops offer?

In addition to helping OSR get off to a stronger start in the face of pigeons and CSFB, companion crops provide complementary rooting, improved moisture retention, early season competition against weeds and soil health benefits - increasing the farm's longer-term resilience.

When is comes to natural pest enemies, a whole-farm approach is key, considering impact of cultivations, insecticides and habitat connectivity across the farm. In addition to parasitoid wasps, this equally benefits other beneficials such as hoverflies, ladybirds and carabid beetles.

Species selection - which should I consider?

Our standard companion crop mix for OSR, combining the complementary traits of buckwheat, berseem clover and fenugreek, remains the most popular choice, but you can speak to our advisors to tailor a mix to your goals and situation. Companion plants are chosen on the basis of efficacy, not being overly competitive with the OSR and ease of destruction by frost or standard herbicide application.

Buckwheat is especially effective at scavenging and mobilising soil phosphorus (P) in forms with low bioavailability, which are then released when the cover crop is terminated.

Legumes, such as berseem clover, can begin to fix nitrogen weeks after establishment, accelerating residue mineralisation and benefiting subsequent crops. In addition, fibrous roots at varying depths help improve soil structure. Micro clovers can be established under the OSR as a living mulch, with additional implications for management in the rotation.

Fenugreek produces a distinctive scent that may help to mask the plant volatiles emitted by OSR, helping to reduce its detectability to CSFB adults during egg-laying periods.

Finally, trials in the UK and Germany suggest that cereals or even cereal volunteers, such as oats, could be an effective companion crop addition for OSR where left for longer than is traditional i.e. after the peak CSFB migration period (Seimandi-Corda, G. et al, 2023). And trials in Switzerland from 2022 to 2024 showed that intercropping OSR with beans reduced CSFB feeding damage, number of Rape Stem Weevil punctures, and number of pollen beetle per inflorescence without negative impact on OSR yield (Magnin., L. et al, 2024)

Tips for planting companion crops in OSR

Drilling the companion just before OSR may be ideal in theory, but in practice in most years - establish them at the same time. This is especially the case in drier conditions, where any soil disturbance before drilling the OSR risks losing vital moisture from the soil.

A multi-hopper drill is ideal, both in terms of moisture retention, seed-to-soil contact and depth adjustment, but broadcasting the companion seed mix into a standing crop is also an option, depending on what kit is available on the farm. However, moisture becomes an even more critical factor, in addition to residue management. Mixing the OSR seed with the companion in one hopper can be done, but requires extra care to avoid any settling out and unwanted gaps in the precious OSR crop itself.

Early establishment (early to mid-August) is best for companions, but late to mid-September timings do not preclude success. In any case, the latest advice for OSR from AHDB is to avoid traditional late-August/mid-September OSR planting timing as this is when peak CSFB migration typically occurs.

Ensure balanced plant densities - enough companion to do the job, but not so much that it competes with the young cash crop. Complimentary rooting systems and a canopy that supports OSR emergence, without shading it out, are key.

Finally, establishing the companion crop as a living mulch - with either a straight or a mix of low-growing clovers, - can also offer a host of benefits. This requires more pre-planning where the living mulch is established in the previous crop, but we have also previously trialled establishing the clover at the same time as the OSR with good results.

🌱 Read our more detailed article on living mulches here →

📞 Speak to one of our advisors on 01480 890686 or email info@oakbankgc.co.uk

Best companion crops for cereals

While less widely used in UK cereals than oilseed rape, a well thought through and managed companion can be beneficial and should not limit yields (which is crucial). Use of pre-emergence residual herbicides significantly limits available options, but our trials in conjunction with Velcourt have highlighted peas, beans and linseed as the strongest contenders for wheat. In oats, vetches offer an option as pre-emergence herbicides are not an issue.

Unless under-sowing a living mulch, establishing the companion and the cereal together will increase chances of success, reduce establishment costs and decrease the likelihood of residual herbicide damage.

Where beans are already part of the rotation, drilling wheat into bean stubble to make the most of the volunteers can work well in our experience. Otherwise, a dual-hopper drill that can deal with different seed sizes and planting depths is beneficial, although not an absolute requirement. Peas can be more straightforward to incorporate due to seed size.

Linseed can more straightforwardly be mixed with the wheat where a more specialist drill is not available, and is not generally affected by common pre-emergence herbicide stacks.

Using companion crops in sugar beet to reduce virus yellows risk

The British Beet Research Organisation (BBRO) has been exploring how companion cropping can contribute to integrated pest management (IPM) in sugar beet, particularly in the fight against virus yellows. Aphid vectors, which transmit the virus, are attracted to young, exposed beet plants. Cereal companion crops, correctly deployed, can help mask the crop and reduce early infestation.

Practical considerations

• Timing - the barley or other companion should be drilled about 5–7 days before the beet to establish enough cover without outcompeting the main crop

• Destruction - companions must be removed early enough to avoid competition and protect yield - typically before the beet canopy closes. BBRO trials have shown that delayed removal will likely lead to yield penalties

• Alternative approaches - in some trials, in-field strips of flowering plants (brassicas and potatoes) or cereals (rye planted as a windbreak) are also being tested for their ability to disrupt aphid movement and provide areas for more targeted management

Does companion cropping work in vineyards and horticulture?

While most UK research and practice has focused on companion cropping in arable systems, interest is growing in applying these principles to other crops - particularly vineyards, orchards, and horticultural systems.

Species selection, timing, and management remain key, always balancing the benefits of biodiversity and soil health against the risk of competition with the main crop.

If you’re exploring companion cropping in a non‑arable system, talk to our team about species and management strategies that work.

Species commonly used in UK and European vineyards, for example, include:

• Low-growing legumes such as white clover for nitrogen fixation and ground cover

• Grasses and deep-rooted herbs to improve structure and avoid erosion

• Flowering strips (e.g. phacelia, buckwheat) in headlands to enhance pollinator and predator habitats

Case studies from Sussex and Kent show improved biodiversity and reduced vineyard floor management costs after just two seasons of companion/cover cropping between vines, provided species are chosen carefully to avoid excessive competition with the vines for water and nutrients.

Optimising companion cropping with maize

Undersowing maize in June around the 5 leaf stage with a mix of grass and clover, ensuring there is no damage to the young maize plants and provided there is adequate soil moisture, can be of benefit to soil structure, following crop nutrition and water quality.

Although this action can't be stacked with CIPM3, following maize with an SFI SOH4 winter cover crop which will not be harvested as a cash crop (but can be grazed) is a good option worth considering even outside of SFI, in the absence of another winter-sown crop.

If you would like to avoid using grass in your undersowing mix, there are other options available. Give us a call to discuss.

Bi-cropping, intercropping, trapping and living mulches

All of the below are included in Defra’s definition of companion cropping under IPM3.

Bi-cropping and intercropping involve growing two cash crops simultaneously. Companion crop under SFI can be harvested, thereby becoming your second cash crop; however, in that case, any herbicides would need to be approved for use on the companion crop, which is different from crop safety. The seed rates will have to be adjusted according to your aims and seed separation costs will need consideration.

Living mulches are permanent companions under cash crops, typically clovers (micro and sub-terranean) persisting for several seasons (see our dedicated article on living mulches for more detail).

Trap cropping is designed to attract pests away from the cash crop. Trials indicate a decrease in CSFB larvae as a function of the proximity to a trap crop. Turnip rape, for example, is typically preferred by CSFB over OSR. It's important to destroy trap crops by the end of February to reduce the risk of them becoming a subsequent source of flea beetle.

Frequently Asked Questions (FAQ)

Can companion cropping help reduce pests in oilseed rape?

Yes - trials have shown that companion species such as buckwheat, clover and fenugreek can help mask oilseed rape from pests like cabbage stem flea beetle and attract natural pest enemies into the crop. It’s not a silver bullet, but it’s part of an integrated pest management (IPM) strategy, alongside species selection, drilling date, seed rate and cultivation.

What are the best companion crops for cereals?

In cereals, legumes such as vetch and clovers are commonly used to fix nitrogen and improve soil health, while supporting biodiversity.

Can you use companion cropping in sugar beet?

Yes - under‑sowing barley or sowing strips of flowering species has shown promise in helping reduce virus yellows by masking young beet plants from aphids. Careful management is required to avoid competition with the sugar beet and research is ongoing.

Is companion cropping suitable for vineyards?

Absolutely - in vineyards, low‑vigour legumes and flowering herbs are often sown between vine rows to improve soil structure, suppress weeds, attract beneficial insects, and support biodiversity. The right species and careful management avoid competition with the vines.

Are companion crops the same as living mulches?

Living mulches are companion crops that are typically permanent under‑sown covers, persisting for several seasons. Read our guide to living mulches here.

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📞 Speak to one of our advisors on 01480 890686 or email info@oakbankgc.co.uk