Potato Cyst Nematode (PCN) remains one of the most persistent challenges facing UK potato growers. Managing it effectively is rarely down to one single action. It requires a joined-up approach, combining accurate soil testing, variety choice, rotation, good crop management and, where required, the responsible use of granular nematicides as part of an integrated pest management (IPM) strategy.
As growers continue to look for ways to reduce PCN pressure while protecting soil health, there is growing interest in biological and cultural approaches that can sit alongside existing control measures.
One area attracting increasing attention is biofumigation. Ongoing PhD research at Harper Adams University is helping to improve understanding of how this technique could be used more effectively in practical potato rotations.
What is biofumigation?
Biofumigation involves growing specific crops, such as Indian mustard, and incorporating their green material into the soil.
Dr Matt Back, nematology expert at Harper Adams University, explains that when these plants are crushed, they release glucosinolates. These natural compounds break down into isothiocyanates, which are gases that can be toxic to soil-borne pests, including PCN.
“Unlike conventional chemical treatments, this approach utilises the plant’s own natural chemistry, offering a more sustainable option for managing nematodes while also contributing to soil health,” says Dr Back.
One of the advantages of biofumigation is its flexibility. Traditional trap crops often require a full growing season, from June through to October. Biofumigant crops, however, can be drilled in late July or early August and incorporated before October, making them easier to fit into commercial rotations.
Dr Matt Back – nematology expert at Harper Adams University,
Making biofumigation work in practice
The success of biofumigation depends on several practical factors. Variety choice, drilling date, crop nutrition, biomass production and soil conditions all play an important role.
Previous work at Harper Adams has highlighted varieties such as Caliente 199, which has been widely studied for its effect on PCN, and the Dutch variety Brons, which has shown promise in partial biofumigation.
To maximise the potential of biofumigation, crops should ideally be sown by late July to encourage strong fresh biomass. Nitrogen and sulphur can also support crop growth and glucosinolate production.
Where full biofumigation is being used, careful chopping and immediate incorporation into moist soil are key. Timing matters, as the crop material needs to be broken down and incorporated quickly to capture the biofumigant effect.
What is partial biofumigation?
Newer research suggests biofumigation may not always rely on full incorporation.
Partial biofumigation is based on glucosinolates being released from living roots while the crop is growing. Soil microbes then break these compounds down into products that may help suppress pests such as PCN.
Dr Back says this could offer practical advantages for growers.
“By reducing the need for intensive chopping and incorporation, partial biofumigation could lower labour demands, offer greater flexibility over timing, and reduce the risk of damaging soil structure in wetter conditions,” he says.
“This matters, because it could make partial biofumigation a more practical option for growers.”
Previous trials have shown varieties such as Bento and Doublet performing particularly well under this approach. Research also indicates that growing these crops can increase the microbial community involved in glucosinolate breakdown.
Which varieties show most promise?
Recent research at Harper Adams, carried out by PhD student Francis Kawalya, compared different oilseed radish and Indian mustard varieties to assess their potential for partial biofumigation.
Nineteen oilseed radish varieties and eight Indian mustard varieties were assessed.
Strong and consistent performers included Caliente 199 and Brons among the Indian mustard varieties, and Doublet, Terranova and Bento among the oilseed radish varieties.
The best-performing varieties shared several useful characteristics. These included stronger roots, higher glucosinolate levels and increased activity from soil microbes involved in glucosinolate breakdown.
This suggests that variety choice could become an important factor in making biofumigation more consistent and practical in the field.
What does this mean for PCN control?
The latest research suggests biofumigation should not be treated as a one-size-fits-all approach. Instead, growers may be able to tailor the technique more precisely by selecting the right varieties and management approach for their rotation, soil type and PCN pressure.
If variety choice, nutrition, crop management and soil conditions can be fine-tuned, biofumigation could offer another useful tool for growers looking to reduce PCN pressure within an IPM programme.
However, it should be viewed as part of a wider strategy rather than a replacement for other control measures.
Simon Alexander, independent agronomist and member of the Nematicide Stewardship Programme group, says the research is becoming increasingly relevant as growers look to combine biological approaches with existing tools.
“As this work develops, growers will better understand not just whether biofumigation can work, but how to make it work within an integrated pest management plan to reduce PCN pressure,” he says.
Responsible nematicide use remains key
While research into biofumigation continues to develop, granular nematicides remain an important tool where PCN pressure justifies their use.
As part of a wider IPM strategy, they should be used responsibly and in line with best practice guidance to protect crops, operators, the environment and future product availability.
Growers using granular nematicides should follow the NSP best practice steps for the application of granular nematicides. which covers key areas including operator qualification, applicator calibration, in-field shut off, spillage management and post-application field checks.
