Title:

Drones can detect southern pine beetle early attack

The southern pine beetle (SPB) (Dendroctonus frontalis Zimmermann; Coleoptera: Curculionidae) is native to the southern U.S., Mexico, and parts of Central America. In southern states, commercially grown pine are vulnerable to SPB attack. In the expanding SPB range, the beetle poses a threat to the pitch pine barren ecosystems which supports globally and locally rare flora and fauna, including threatened and endangered species. The future of the pine barrens depends on forest management responses to SPB. Currently, forest managers use tree decline symptoms to guide SPB suppression activities, typically relying on canopy color change from green to yellow to red and assuming the attacks are highly localized on neighboring trees, forming discrete “spots.” However, at the northern SPB range edge on Long Island, New York, recent observations indicate that needle color is a less-reliable indicator of attack age and beetle developmental phenology. Southern pine beetle spots also appear to be much more diffuse in northern sites. As such, current decision-making practices based on the regularity of these long-observed patterns may not be suitable for management in the expanding SPB range. We quantified needle color change and spatial patterns of attack on Long Island in 2022 using both ground surveys and unmanned aerial vehicles (UAVs, or drones). We compare the results of ground surveys—including repeated tree-level assessments of SPB developmental phenology—with visible-light and multispectral UAV imagery. Our work provides data to support previous observations, and illustrates the utility of UAVs in detecting SPB infestations. We successfully detected early SPB attack using UAV-collected multispectral imagery and balanced random forest classification.

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