Botrytis Bunch Rot. The silent enemy.
Botrytis bunch rot can cause significant crop loss and quality problems, particularly around flowering and as berries ripen. Infection can damage flowers and young bunches, while later infections can spread between berries and rapidly deteriorate bunches. Botrytis can also compromise fruit quality and wine quality, making timely management particularly important when weather and bunch conditions become favourable.
Our Mission & Values
Trust & Data Transparency
We provide clear, auditable insights that empower vineyard managers to make informed decisions with complete visibility into the underlying models.
Grower-First Design
Our tools are built by and for viticulture professionals, focusing on practical usability in the field and the unique needs of vineyard management.
Responsible AI in Viticulture
We use artificial intelligence to enhance human expertise, not replace it, ensuring that technology serves as a reliable adviser for seasonal planning.
How Viti Pulse Models Botrytis Risk.
A mechanistic approach to Botrytis forecasting
Botrytis bunch rot is difficult to predict because risk changes with vine growth stage, weather and the availability of infection sources.
Viti Pulse uses the mechanistic model developed by González-Domínguez et al. (2015), which was developed specifically to describe Botrytis infection pathways in grapevines.
Growth stage matters
Botrytis does not behave the same way throughout the season. The model therefore divides the crop into different infection periods:
-
SEV1 — early season: from visible inflorescences through early berry development. This represents infection risk to inflorescences and young clusters.
-
SEV2 — ripening berries: represents the risk of infection of berries by Botrytis conidia.
-
SEV3 — berry-to-berry spread: represents infection through Botrytis mycelium spreading between touching berries.
This means the same weather event can have a very different significance depending on where the vines are in their development.
Weather is only part of the story
Botrytis needs suitable environmental conditions, particularly moisture and suitable temperatures, but weather alone does not determine disease risk.
The model also considers the potential availability of Botrytis inoculum and the different infection pathways that operate at different growth stages.
Viti Pulse uses hourly weather data to derive a daily moisture/wetness measure for the model. An hour is considered wet when there is:
-
≥0.2 mm rainfall, or
-
relative humidity ≥95%, or
-
leaf-wetness probability ≥50%.
This is a Viti Pulse adaptation that allows the published model's moisture requirements to be represented using hourly weather data.
Three Botrytis risk measures
Rather than reducing everything to one number, Viti Pulse keeps the three model outputs separate:
SEV1
Early-season infection risk affecting inflorescences and young clusters.
SEV2
Risk of infection of ripening berries from Botrytis conidia.
SEV3
Risk of berry-to-berry infection where berries are in contact and Botrytis can spread through mycelium.
Together, these provide a more useful picture of which Botrytis pathway is currently most relevant.
Why a distinct "infection gap".
While Botrytis cinerea can successfully attack early in the season during flowering (E-L 19–26) and again late in the season during ripening (E-L 35–38), it seemingly disappears or stalls out during the green, hard berry stages.
The "infection gap" occurs because green berries turn into an incredibly hostile environment for the fungus. young green berries produce powerful antifungal compounds (such as resveratrol and proanthocyanidins).
When a botrytis spore infects the tissue during flowering or early fruit set, these natural plant defense chemicals physically halt the growth of the fungal mycelium.
This is arguably the most vital chemical spray timing in a botrytis program.
Once bunch closure (E-L 33) occurs, the berries pack together tightly. Any latent botrytis spores resting on the internal stems (pedicels and rachis) from flowering will be permanently sealed inside the bunch.
Later at veraison (E-L 35), as the berries soften, acid drops, and sugars rise, those hidden infections wake up and rapidly rot the bunch from the inside out.
Dropping a protectant or systemic fungicide right before the bunch closes is your last chance to coat the interior fruit surfaces.
What does a high Botrytis risk mean?
A high risk reading means that the environment and crop stage are favourable for the relevant Botrytis infection pathway.
It does not mean that bunch rot will definitely develop.
Actual disease will also depend on factors such as:
-
Botrytis inoculum being present
-
canopy and bunch microclimate
-
bunch compactness
-
berry damage or wounds
-
variety susceptibility
-
vineyard management
Why Viti Pulse uses this approach
A simple rule such as “X hours of wetness = high Botrytis risk” does not capture the biology of the disease.
Viti Pulse instead asks:
Where are the vines in their development?
Is the weather favourable?
Which Botrytis infection pathway is active?
How strong is the resulting infection risk?
The result is a Botrytis forecast designed to tell growers why risk is increasing or decreasing, rather than simply reporting whether the vineyard is wet.
Scientific basis: González-Domínguez E, Caffi T, Ciliberti N & Rossi V. (2015), A Mechanistic Model of Botrytis cinerea on Grapevines That Includes Weather, Vine Growth Stage, and the Main Infection Pathways, PLOS ONE 10(10): e0140444.