Late-season vigilance vital as Botrytis risk builds towards grape harvest

Recent rainfall has increased the risk of Botrytis in British vineyards, with grapes now entering a particularly vulnerable stage as they ripen and approach harvest.

After an exceptionally dry summer, wetter conditions have returned across much of the country. England recorded its wettest week since early February in the first week of September, a shift that could prove significant for vineyards approaching harvest.

Rainfall can leave bunches wet and increase humidity within the canopy, creating conditions favourable for Botrytis infection, says Matt Greep, Agrii Area Business Manager for Fruit.

“With harvest approaching, growers need to stay vigilant and assess Botrytis risk based on local weather, vineyard conditions and crop development,” he says.

Good canopy management remains an important cultural control, helping to maintain airflow around bunches and reduce the time they remain wet. However, where disease pressure is increasing, a late-season fungicide may also be required.

Pre-harvest intervals narrow treatment options

One of the main challenges this close to harvest is the pre-harvest interval associated with many conventional fungicides.

Matt says this makes product choice particularly important as growers move closer to picking.

“Botector is one option growers can consider at this stage,” he says.

The biofungicide contains *Aureobasidium pullulans* and has a pre-harvest interval of just one day, giving growers greater flexibility where late-season Botrytis protection is needed.

How Botector works

Botector differs from biofungicides that act by producing antimicrobial compounds against target pathogens.

Instead, *A. pullulans* colonises the surface of leaves and fruit, competing with Botrytis for space and nutrients.

Samuel Caygill, Product Manager at SAN Agrow, says the organism is well suited to the conditions in which Botrytis risk increases.

“Because *A. pullulans* is a yeast-like fungus, it thrives under the same conditions that favour Botrytis,” he says.

“When humidity goes up, triggering the spread of Botrytis in grapes, *A. pullulans* is able to rapidly colonise and protect bunches before infection develops. It gets ahead of the pathogen.”

He recommends applying Botector ahead of forecast rain, ideally around two days beforehand.

“This means that when the conditions are right for Botrytis to start multiplying, Botector is already one step ahead to protect the grapes from rotting,” he says.

“The pathogen cells may still be there; they just can’t grow enough to form a rot and damage the quality of the grapes.”

Protecting crop quality ahead of harvest

SAN Agrow trials have found that Botector has no impact on the vinification process, and the product is already used extensively in vineyards internationally.

Matt says that flexibility could prove particularly useful in the closing stages of what has otherwise been a strong season for British wine.

“2026 is currently shaping up as a potentially very good vintage for British wine,” he says.

“However, rain this close to harvest presents the biggest threat to what has otherwise been an excellent season.

“In Botector, we have a biological product available that gives excellent protection from Botrytis, with a label that allows us to safely apply it this late in the season.

“I’d encourage growers to consider applying it in the next few weeks to protect their investment.”