C-DRONE GUIDE · 2 AUGUST 2026
Spruce bark-beetle detection by drone multispectral: spotting attacks before browning, price
The spruce bark beetle has devastated spruce stands: an attacked tree stays green for weeks before browning, and by the time it turns red the beetles have already left to colonise the neighbours. The whole sanitary challenge is to spot attacks early, to fell and remove the wood before emergence. The multispectral drone offers a fine reading, stand by stand, between ground surveillance and satellite. Here is what it really detects, at which stage, its honest limits, and the prices observed in 2026.
Published on 2 August 2026, reviewed on 6 August 2026 — regulations in force as of August 2026.
Red, green, and the race against emergence
An attacked spruce goes through stages: green attack (the tree is colonised but its crown stays green — invisible to the eye), then browning, then needle fall. To the eye as on a normal photo, only the red stage shows — too late. The value of multispectral is to catch early signals in the near-infrared and red-edge, before the visible colour changes, while felling can still prevent spread.
A study by Klouček, Modlinger, Zikmundová, Kycko and Komárek published in 2024 in Frontiers in Forests and Global Change tested drone multispectral imagery on a Czech spruce stand at various stages: the NDVI and BNDVI indices identify infested trees with sensitivities reaching 90%, far better than individual bands alone (see the study on Google Scholar). The message stays cautious, though: green-attack detection is not always reliable enough to stand alone operationally.
The drone between the ranger and the satellite
Three scales complement each other. Human surveillance remains the field reference but cannot cover everything. The satellite sweeps vast massifs but with limited resolution and revisit. The drone sits in between: it treats a stand or an at-risk sector tree by tree, on demand, at the right time of year. Its role is not to replace the ranger's round but to target it — flagging suspect crowns to check at the base.
This scouting logic extends our guide to forestry drone inventory and health monitoring, of which the bark-beetle crisis is a major use case. On the same flights, you can feed a forest inventory or track a plantation's establishment, pooling the acquisition.
Honest limits and ground-truthing
One must be clear about what the method promises. Green-attack detection remains hard and condition-dependent: some stresses (drought, other pathogens) produce similar signatures, and reliability varies with timing. The drone flags suspect trees, not entomological proof: confirmation goes through examining the trunk (entry holes, boring dust, bark). An honest provider states detection rates, not certainty.
Good practice is a pairing: multispectral mapping to rank sectors, then foot verification of flagged crowns, and finally a sanitary decision (felling, debarking, removal) taken by the manager. The drone's value is to concentrate human effort where it counts, on massifs where walking every hectare is impossible.
Prices observed in 2026
Ranges observed in 2026 (excl. VAT):
- Multispectral overflight of an at-risk sector (targeted stands, suspect-tree map): €700 to €2,000 by area and terrain.
- Massif campaign (several hundred hectares, at optimal dates): on quotation, often a declining per-hectare package.
- Repeated in-season monitoring (several passes to catch the stages): a series package.
- Ranked report and support for ground verification: extra.
Timing beats price: one flight at the right stage is worth more than ten ill-timed ones. Our drone mapping and monitoring page presents vegetation remote-sensing services; request a quote stating the species, the area and the massif's sanitary history.