G4TF trials back integrated strategy for powdery mildew control

In the second of our Growing for the Future series, Fruit Grower looks at the latest, encouraging results from trials testing integrated strawberry disease control programmes combining both conventional and biorational fungicide products.

Industry confidence is building that strawberry growers do not need to sacrifice marketable yield to reduce reliance on conventional disease control chemistry.

That certainty is being underpinned by a series of NIAB East Malling trials, designed to test how far integrated programmes can go in balancing efficacy, yield and residue reduction demands.

Led by manufacturer Certis Belchim, the work compares conventional fungicide programmes with Growing for the Future (G4TF) approaches that integrate biorational products alongside standard chemistry.

Biorationals include Bacillus product Amylo-X (Bacillus amyloliquefaciens strain D747) and fully formulated potassium hydrogen carbonatefungicide Karma.

For the firm’s horticulture technical manager Alex Cooke, the starting point is clear – the trials are not trying to show how to replace conventional chemistry, but where it can be used more strategically.

“It’s about reducing reliance, not removing conventionals completely. Chemistry has a key role to play, particularly early in the programme.”

“What we’ve been looking at over the past five years is how you build a programme that ‘starts clean’ with conventional products like Takumi (cyflufenamid), and then integrates biorationals through the season, particularly as you move towards harvest.”

Under pressure

The 2025 trials focused on powdery mildew control in the variety Malling Centenary, using a deliberately high-pressure scenario to give programmes the stiffest of tests.

Plots were artificially inoculated and supported with irrigation to help drive infection, resulting in extreme disease levels in untreated controls.

Alex notes that by the end of the experiment, there was close to 90% mildewed fruit in the untreated.

“Nothing was going to look good under that level of infection and it’s important to say that this is artificially high pressure. In a commercial crop, you’d never allow mildew to get anywhere near that severe.”

Despite the extreme pressure applied in the trial, the relative performance of programmes remained clear and in line with previous seasons where meaningful disease pressure was present.

Across the season, both G4TF programmes tracked closely with the conventional standard, particularly through the early and mid-season when control is most critical.

“What we see is that the integrated programmes hold mildew down early on, and even as pressure builds, they stay well below the untreated.”

“At key timings, the G4TF programmes were roughly half the infection level of the untreated, and towards the end they’re broadly in line with the conventional,” explains Alex.

Marketable yield

Crucially, that disease control translated into the key commercial metric for strawberry producers – Class 1 marketable yield.

“When you look at the total harvested yield, the Growing for the Future programmes were slightly higher than the conventional and from a Class 1 perspective, there was no significant difference.”

“So, it showed you can reduce reliance on conventional chemistry without sacrificing marketable fruit.”

Alex stresses that Class 2 fruit is worth very little, so any uplift in total yield is not commercially significant.

However, he suspects that the observation in this trial could be attributed to the overall plant health benefits which are often seen when using some biorationals, particularly Bacillus-based solutions.

“Products like Amylo-X act as elicitors, improving plant health, root development and stress tolerance, giving you a stronger crop overall.”

Post-harvest quality

Post-harvest latent rot testing of fruit showed that integrated programmes performed similarly to conventional treatments in limiting botrytis and other storage diseases.

“For me, that was encouraging. It shows that these products are doing something beyond what you can see in the field,” says Alex.

He sees both Amylo-X and Karma contributing to that effect.

“Karma plays a role and in France, for example, Karma is used as much in Botrytis programmes as it is for mildew.”

“However, Amylo-X clearly influences latent rots and is probably the stronger contributor of the two, and that’s why it’s on the product label,” he explains.

Formulation matters

One of the clearest findings from the work was the performance gap between formulated Karma – which combines the active with the right wetters – and commodity substance alternatives.

Treatments comparing six back-to-back Karma treatments with six applications of the commodity potassium bicarbonate highlighted a consistent advantage.

“You’ve got about 11% more Class 1 fruit from Karma and when you look at infection levels, it’s about 14% versus 27% with the commodity potassium bicarbonate. That’s a big difference.”

Attempts to close that gap by adding adjuvants to commodity bicarbonate have largely fallen short in practice, notes Alex.

“The feedback from agronomists is that even when you mix in a wetter, it still doesn’t perform like Karma. It comes back to formulation.”

Bacillus performance

The trials also provided a useful benchmark for Bacillus-based products. When used alone, differences between products became more apparent, particularly on leaf infection.

Alex says there was a clear separation between Amylo-X and some of the other Bacillus products in terms of leaf mildew control.

“It’s not as strong as a conventional fungicide, but you wouldn’t expect it to be. The key point is how it performs within a programme.”

That advantage comes down to how the product is produced and behaves on the plant.

“Due to its unique fermentation process, Amylo-X contains a high level of lipopeptides, which gives immediate antifungal activity when applied,” he explains.

“There are three main modes of action – that immediate activity, then a biofilm that protects the leaf once the bacteria colonise and then induced plant resistance. But it’s really that first effect that makes it stand out.” By contrast, some competitor Bacillus products rely more heavily on colonisation.

“With other products, the bacteria need to establish on the leaf before they start producing those compounds, and that process very much depends on environmental conditions.”

“High UV, low humidity and drying conditions in tunnels can make it difficult, so having that immediate activity gives Amylo-X an advantage.”

Programme design

A final key takeaway from the trials is that success can depend on programme structure rather than individual product performance.

“There’s no silver bullet. It’s about how you sequence products and how you respond to pressure,” says Alex.

Early control remains critical, with conventional chemistry playing a major role in establishing a clean start. From there, biorationals can be layered in to maintain control and manage residues.

“In hindsight, there are always tweaks you’d make once a trial concludes. For example, bringing Karma in earlier in the G4TF programmes would probably have flattened the curve even more.”

Next steps

For 2026, the focus will shift towards more commercially realistic demonstration trials.

That includes running longer-season everbearer crops without artificial inoculation and integrating decision support systems to guide spray timing.

“We want to show how these programmes perform in a real-world situation and give growers the information they need to confidently fine tune, whatever the season brings,” Alex concludes.

Agronomist’s view: Andrius Kumstys, Berry Gardens Growers

Berry Gardens Growers head of agronomy Andrius Kumstys says the NIAB East Malling trials have provided valuable, practical insight into how biorational products can be used effectively in commercial disease control programmes.

So much so that the grower co-operative invited Certis Belchim’s Alex Cooke to present the results at its annual technical conference.

“As agronomists, we already know these products can work but seeing them compared side by side under the same conditions gives you much more confidence – and also shows what not to do.”

That is particularly important as growers face tightening residue limits and increasing pressure on product choice.

“In reality, these products are not replacing chemistry, but they are becoming essential tools, especially during busy harvest periods when it’s difficult to fit in sprays with longer harvest intervals.”

In practice, however, success depends heavily on timing. He says if you use them at the wrong point, under high disease pressure, you can get into trouble.

“It’s all about using them strategically,” Andrius adds.

He typically starts with conventional chemistry to clean crops, before introducing biorationals as pressure eases or during harvest. If conditions turn, he switches back.

“You must be flexible. There’s no fixed programme.”

He adds that performance improves when products are used in sequence with two or three applications of Amylo-X in a row to build up protection.

“That cumulative effect is where Bacillus products really start to work and combining products can also strengthen control.”

“Karma is more eradicant, while Amylo-X is more preventative, so using them together helps cover both sides. Infection and protection,” he explains.

For Andrius, the trials highlight both the opportunity and the challenge.

“They show these programmes can work, but also that how you use them is just as important as what you use.”

This article originally appeared in The Fruit Grower, May 2026.