Project Overview

Reports

Commodities

Target Pests

Practices

Hairy willow-herb (HWH) is an invasive perennial forb common in the northeastern US, around the Great Lakes, and in several western states (Figure 1; EDDMapS 2024). It often forms dense monotypic stands that clog waterways, exclude native vegetation, and degrade habitat for wildlife (Stuckey 1970; CDA 2015). As a List A noxious weed in Colorado (CDA 2025), HWH is the target of eradication efforts wherever it occurs. While there are effective treatment options (CDA 2015), detecting HWH is difficult when it is interspersed with other wetland vegetation (Figure 2; Figure 3), particularly when working in larger, difficult to access wetlands (Fort Collins, Larimer County, and Weld County, personal communication). Remote sensing using unmanned aerial systems (UAS) is one potential solution to this problem, but there has been limited research into UAS-based detection of HWH. The primary objective of our project is to implement and evaluate UAS-based remote sensing methods to detect HWH and identify techniques that can help managers detect smaller infestations of HWH in larger wetlands, intervene earlier in the invasion, monitor treatment effectiveness, and increase the likelihood of successful HWH eradication. The proposed project will focus on HWH mapping and management, but UAS applications have immense potential to advance vegetation management, and the techniques we implement and evaluate are likely to have applications to other invasive plants.

In addition, we will: (1) examine environmental characteristics that may contribute to HWH invasion (e.g., local topography and co-occurring vegetation); and (2) document ongoing efforts to apply herbicides using UAS. The UAS-collected data we obtain will permit investigation of environmental characteristics that contribute to the suitability of different habitats for HWH invasion, and this could help managers target future monitoring and increase the likelihood of early detection. Northern Colorado weed managers are currently using UAS to treat HWH and other invasive plants, and UAS applications have recently been adopted in some county weed management plans (Boulder County 2024). We will document UAS-based invasive species detection and management, and highlight these activities in an outreach document published and disseminated through Colorado State University (CSU) Extension, and a stakeholder meeting/west-wide webinar to increase regional impact.

To achieve these objectives, we will work with partners (Fort Collins, Larimer County, and Weld County) to identify at least three research sites invaded by HWH. We will conduct three flights at each site: once early in the summer, when HWH is small compared to other vegetation (late-June/early-July); once later in the summer when HWH is larger and comparable to other vegetation (late-July); and once in August/September, after herbicide has been applied to HWH. The first two flights will evaluate mapping techniques at different timings relative to HWH and other vegetation phenology. Data from the third flight will be post-treatment to document the effectiveness of UAS-based herbicide applications. Mid-summer field vegetation surveys will provide additional validation of UAS-collected data products. We expect all field activities to be completed by early- September 2026, and the outreach document, stakeholder meeting/webinar, and project report will be completed by February 28, 2027.

Objective 1: Implement and evaluate UAS-based remote sensing methods to detect hairy willowherb (HWH) when it co-occurs with other wetland vegetation.

Objective 1a: Use UAS and field vegetation inventory data to identify key phenological and structural characteristics, flight parameters, and mapping techniques to enable accurate and efficient mapping of HWH.

Objective 1b: Use UAS and field vegetation inventory data to examine HWH distribution patterns and identify unique environmental characteristics (e.g., topography and co-occurring vegetation) of areas invaded by hairy willow-herb.

Objective 1c: Use UAS mapping of HWH to monitor treatment effectiveness at reducing the abundance of HWH.

Objective 2: Demonstrate the effectiveness of UAS-based applications for invasive plant management (integrated assessment, treatment, and monitoring) to local stakeholders and regional weed management professionals through an outreach document and webinar advertised, published, and disseminated through CSU Extension.

Objective 2a. Document a workflow to produce invasive species maps using UAS, with HWH as an example, including flight parameters and procedures to collect UAS imagery, processing the collected imagery, and statistical methods to map and evaluate accuracy.