Why regulatory changes are needed for biopesticides
© Tim Scrivener Increasingly innovative and sophisticated biological-based crop protection is emerging from research programmes, but both the regulatory system and on-farm knowledge of how to use such products are struggling to keep up.
Endophytes, elicitors, arbuscular mycorrhizae and bacteria and fungi species within the soil microbiome all have potential to help growers with disease control in crops (see “Three alternative biological-based disease control solutions”).
But as research continues to improve understanding of how biological control can be applied, it is clear the regulatory system, especially outside of the US, is not fit for purpose, claims independent biopesticide expert Roma Gwynn, director of Biorationale.
See also: Analysis: How Brexit affects farmers’ access to pesticides
“The regulatory system is struggling to cope even with the most basic applications, while innovation is starting to move beyond that.”
Indirect or augmentative control from biological systems is particularly challenging for regulatory systems, she says.
Lovely research
“There’s some lovely research happening – for example, in maize in Brazil, the beneficial fungus trichoderma is applied as a seed treatment to maize, and encourages the plant to send out signals that attract the natural enemy of the fall armyworm.”
Another example was the development of a product based on a hormone wheat releases to attract lacewings to predate on aphids. “It’s not for the direct, but for the next indirect effect. This is where the technology is moving to.”
But multiple modes of action and indirect system outcomes makes regulation more complicated than for chemistry, where it is often a simple cause and effect to show and measure benefits.
While the biological market is growing rapidly – increasing by more than 300% in the 10 years to 2018, albeit from a low base – regulation, which is tweaked from that for chemicals, is a key barrier, she says.
Approval for micro-organism active substances in the EU is taking five to 10 years, rather than the target nine months to one year. “The substances that have got through have done so despite the system, rather than because of it.
Roma Gwynn’s reasons why the EU regulatory system is failing
- Triplicate system involving member state, European Food Safety Authority and EU Commission
- Uses precautionary principle rather than “generally regarded as safe”
- Same regulatory system as chemistry – all products in same system
- Lack of funding in biological crop protection expertise in regulatory agencies
- Precautionary principle and lack of expertise means more questions than necessary asked before a decision is made
- Results in approvals getting stuck in system despite much less data than for chemicals
“I’m trying to get new active substances into the system, and I can’t get a slot until at least 2024. The effect is that companies are writing Europe off their marketing lists – it’s too complicated, too expensive and too unpredictable.
“And I fear it will be even more acute in the UK, as most companies will not pay a second set of fees to get approval in the UK as well.”
Compared to the rest of the world, this process only takes two years from submitting a regulatory dossier to getting approval for use by a farmer, she says.
Post Brexit, the UK could improve access biological crop protection with a new regulatory approach, Dr Gwynn stresses. One of the key differences in other countries with faster regulatory systems is the use of expert evaluators.
“The UK government does have an opportunity to set up a separate group of experts who deal with these technologies, and if that happens it will make a big difference.”
Three alternative biological-based disease control solutions
1. Elicitors
Elicitors are naturally occurring compounds that trigger a plant to produce a defence response when it perceives it is under attack.
This technique is being investigated for the ability to reduce fungicide use in barley by Neil Havis, senior plant pathologist at Scotland’s Rural College.
“We’re trying to induce the defence response in the crop before the pathogen attacks, which suggests we will get most response from earlier timings.”
Trials of various potential elicitors as either seed treatments or foliar applied options at T0 in combination with reduced doses of fungicide have shown some promise, he says.
“In these trials, the cost of a full fungicide programme was £51/ha compared with the elicitor, plus reduced fungicide at £39/ha, so there is a potential economic benefit.
“But their integration will require some careful management as control is more variable, which will be harder to sell to growers.”
2. Microbiome
The microbiome is made up of fungi, bacteria and other microbes that live in association with a plant, either inside it, on its surface or within the immediate vicinity.
“The soil microbiome has the potential to contribute to more environmentally benign agriculture,” suggests Rothamsted Research’s plant and soil microbiologist Tim Mauchline. “It is well-known that soil-dwelling microbes can influence plant health, growth and resource use efficiency of plants.”
Research techniques, such as DNA sequencing and culture-based studies, are helping unravel how management practices such as fertiliser regimes, land management and varietal characteristics influence the microbial population structure and function in the soil and root microbiome.
“Understanding the beneficial functions of microbes could potentially help lead to reductions in agchem use,” Dr Mauchline suggests.
Research comparing non-fertilised and fertilised wheat showed that 93% of microbes in non-fertilised wheat had a plant growth promoting function, such as being able to solubilise iron, phosphate or potassium, compared with just 19% in a fertilised wheat.
“The selection of those beneficial microbes means we should rethink about how much fertiliser we need to add to the system.”
Further research into take-all indicates that wheat variety could differentially influence build-up of take-all pathogen inoculum. When analysing the root microbiome, surprisingly it was found that an increased diversity of bacteria known to combat take-all disease resulted in poorer control of the take-all fungal pathogen.
Analysis of the genomes of bacteria associated with a high take-all wheat variety were to possess more genes that were adapted to be on a “war-like” footing against other microbes, which Dr Mauchline presumes allows them to access nutrients from the prematurely senescing plants.
However, the genomes of bacteria isolated from a low take-all building variety possessed more genes encoding functions deemed to be beneficial to healthy wheat growth.
Taken together, these research approaches could provide a platform to decipher the best choice of wheat variety to combat take-all disease with reduced mineral fertiliser inputs.
3. Endophytes
The dilemma with endophytes, which are microbes that live inside a plant host at some point in their life and also part of the microbiome, is how they colonise plant tissues without causing an apparent harm to their host, says researcher Matevz Papp-Rupar from Niab East Malling Research.
“It’s balanced antagonism,” he says. The outcome for the plant and endophyte, whether it is beneficial for either, is dependent on the environment, endophyte strain and plant, and can change from one situation to another.
Their potential to be used as biofungicides requires four things, he says. “They must be easily applied to crops, have an effective mechanism, be easily identified and commercialised, and never cause symptoms in the host.”
Finding endophytes that meet those criteria is challenging, but Dr Papp-Rupar has made promising progress with Epiococcum purpurascens to control European apple canker – a disease that’s hard to control with fungicides.
“It does control apple canker, it colonises apple trees, but needs multiple sprays and will only last one season.”
Other applications of endophytes include as seed treatments to improve nutrient use efficiency.
Amber project suggests biofungicide use could be improved
A lack of tools and knowledge is holding back the successful use of biofungicides in horticulture, says Dave Chandler, a microbiologist and entomologist at the University of Warwick.
Biofungicides should be used in programmes with the objective of reducing conventional fungicide applications, he suggests.
But a key finding from the AHDB’s Application and Management of biopesticides for efficacy and reliability (Amber) project is that application advice and effective equipment for precision application is lacking.
“The spray equipment is mostly not fit for purpose in horticulture,” Dr Chandler says. “There is no point spending millions on developing a product if the grower cannot apply it to a crop effectively.”
Labels are difficult to follow, and there is a lack of accessible underpinning information about persistence, the environment the biopesticide works best in, and its effective dose, which shockingly is often not known, he says.
While biopesticide companies are working to address those gaps, he says, the Amber project ran two practical workshops in conjunction with Silsoe Spray Applications Unit to help 100 growers and agronomists with good spray application principles.
There is a lack of knowledge about how to use biology-based integrated pest management. Many growers believe these biopesticides are equivalent to conventional chemistry, but biopesticides are not as forgiving as conventional chemistry, he says.
“Biopesticides tend to be contact-acting, so if your spray application is poor, you won’t hit the target and they will fail,” says Dr Chandler.
“In particular, label water volumes are too high. They’re often 1,500-2,000 litres/ha, which is inefficient to apply and often you’ll get significant loss of product through run-off.
“For best results, you need to control water volume to get the highest concentration of product in the target zone on the leaf surface.”
Amber has also been reviewing precision agtech equipment for its potential to help in the sector, he says.
“Smart decision support systems using tech, such as low-cost sensors, cloud-based algorithms, dashboards and mobile phones, will help in future to know when and how to use biofungicides.”
Arable and horticultural growers could learn from each other’s experiences, he adds.
“The arable sector lags behind horticulture in its use of biofungicides, despite being more advanced in its spray equipment. There’s a lot the arable sector could learn from protected crops about reducing chemical use,” he suggests.
All speakers presented at the BCPC Diseases Review
