C-DRONE GUIDE · 6 SEPTEMBER 2026
Botrytis and noble rot by drone: mapping the risk, timing the successive picks
Around the Sauternais, the Ciron — a cool tributary of the Garonne — triggers a thermal shock each autumn that produces morning mists which clear as the day warms up. That precise cycle, morning humidity followed by dry afternoon heat, is what lets Botrytis cinerea develop into noble rot rather than the destructive grey rot — the same fungus, two opposite outcomes depending on the weather and the terroir. Across the 1,200 hectares of Sauternes and Barsac, as on the late-harvest vineyards of Alsace or Jurançon, that balance forces growers into successive picks, bunch by bunch or even berry by berry, sometimes five to nine passes over a full month. On an ordinary vineyard not aimed at a sweet wine, by contrast, the same fungus is simply a threat to catch early. Here is what a multispectral drone survey brings to both cases, and what it does not replace.
Published on 6 September 2026, reviewed on 11 September 2026 — regulations in force as of September 2026.
One fungus, two opposite outcomes
Botrytis cinerea is one of the most widespread vine diseases in the world. On an ordinary vineyard it takes the form of grey rot (Botrytis bunch rot): it attacks ripe berries, cuts yield and degrades wine quality, with losses that can turn severe in a wet year. On certain terroirs, by contrast, the very same spores produce a prized noble rot: the fungus pierces the berry's skin, water evaporates, and sugars, acids and aromas concentrate. That mechanism is what produces Sauternes and Barsac, Alsace's late-harvest and Sélection de Grains Nobles wines (Gewurztraminer, Pinot gris, Riesling, Muscat), or sweet Jurançon.
The swing between the two outcomes hinges on a precise weather balance: around the Sauternais, the Ciron, whose water stays at 11-13°C in autumn against 17 to 18°C for the Garonne, produces a thermal-shock morning mist that must clear as the morning goes on. Without the dry, warm afternoon that follows, the same fungus turns to grey rot. That fine dependence on microclimate explains why a single estate can see a lower, damper plot succumb to grey rot while an exposed plot a few hundred metres away develops perfect noble rot.
What a multispectral flight detects before the grower's eye does
A team led by Sergio Vélez published in 2023, in the journal European Journal of Agronomy, a method for mapping the spatial variability of grey-rot risk from drone-borne multispectral imagery (see the study on Google Scholar). The idea: water stress, vigour and canopy density — all measurable by drone — correlate with the zones where botrytis is most likely to develop, before symptoms become visible at all.
More recently, a team led by Guillem Montalban-Faet published in January 2026, in the journal Sensors, a method for direct detection of Botrytis cinerea using a chlorophyll-absorption index (CARI) combined with a deep-learning detection model (YOLO): 92.6% precision, 89.6% recall, a 91.1% F1 score (see the study on Google Scholar). Chlorophyll degradation in affected tissue changes the leaf's and berry's spectral signature before rot becomes visible to the eye from the row — a usable signal from the very first outbreaks, across dozens of hectares in a single flight, where a walking inspection covers only one row at a time.
Two opposite uses for the same tool: treat early, or pick at the right moment
On an ordinary vineyard, a risk map is used to act quickly: targeting a spray pass or leaf-thinning on the highest-risk zones alone rather than the whole plot, or steering sorting at harvest reception toward lots from flagged sectors. It is the same vigour-mapping logic detailed in our guide to vineyard water stress by drone, applied here to disease risk rather than irrigation.
On a sweet-wine terroir, the use flips: the goal is no longer to avoid botrytis but to track its progress in order to time the successive picks — five to nine passes sometimes needed in the Sauternais, spread over about a month. A flight repeated weekly through the over-ripening period gives the vineyard manager an overview: which plots have reached a noble-rot level worth sending the pickers to first, and which still need time. The drone still replaces neither tasting nor a refractometer check of sugar content: it says neither the exact must weight nor whether a given berry's rot has stayed noble rather than turned grey — both decisions the grower still makes with a bunch in hand.
Who commissions this kind of mission, method and 2026 prices
These flights are commissioned by estates in the Sauternais and Barsac, Alsace producers of late-harvest and Sélection de Grains Nobles wines, Jurançon properties, and ordinary estates looking to limit losses in a high-botrytis-risk year. Sensor choice follows a trade-off close to the one detailed in our guide to multispectral vs RGB cameras: multispectral for risk mapping and early detection, high-resolution RGB alongside it to visually confirm a sector's state before sending a picking team there. On estates with steep plots, the same access constraint as in steep-slope spraying applies to the mapping flight.
Ranges observed in France in 2026, excl. VAT:
| Service | Range (excl. VAT, 2026) |
| One-off multispectral flight, risk mapping (up to 15 ha) | €300 to €600 |
| Weekly monitoring through over-ripening (3 to 5 passes) | €1,200 to €2,500 per estate |
| Combined multispectral + high-resolution RGB mapping | €450 to €900 per pass |
| Multi-year monitoring built into managing successive picks | quote-based, by area and frequency |
These amounts cover the flight, index processing and map delivery; they exclude sugar-content checks, tasting, and the decision to start a pick, which remain the responsibility of the vineyard manager or the winemaker. For an estate, a domaine or a cooperative winery, request a quote stating the area, the grape variety and the goal (disease risk or noble-rot monitoring).