Calibration of an Herbicide Ballistic Technology (HBT) Helicopter Platform Targeting Miconia calvescens in Hawaii

By James J. K. Leary, Jeremy Gooding, John Chapman, Adam Radford, Brooke Mahnken, and Linda J. Cox. 
Published in  2013. Invasive Plant Science and Management: April-June, Vol. 6, No. 2, pp. 292-303. http://wssajournals.org/doi/abs/10.1614/IPSM-D-12-00026.1

Abstract

Miconia (Miconia calvescens DC.) is a tropical tree species from South and Central America that is a highly invasive colonizer of Hawaii's forested watersheds. Elimination of satellite populations is critical to an effective containment strategy, but extreme topography limits accessibility to remote populations by helicopter operations only. Herbicide Ballistic Technology (HBT) is a novel weed control tool designed to pneumatically deliver encapsulated herbicide projectiles. It is capable of accurately treating miconia satellites within a 30 m range in either horizontal or vertical trajectories. Efficacy was examined for the encapsulated herbicide projectiles, each containing 199.4 mg ae triclopyr, when applied to miconia in 5-unit increments. Experimental calibrations of the HBT platform were recorded on a Hughes 500-D helicopter while conducting surveillance operations from November 2010 through October 2011 on the islands of Maui and Kauai. Search efficiency (min ha−1; n  =  13, R2  =  0.933, P< 0.001) and target acquisition rate (plants hr−1, n  =  13, R2  =  0.926, P< 0.001) displayed positive linear and logarithmic relationships, respectively, to plant target density. The search efficiency equation estimated target acquisition time at 25.1 sec and a minimum surveillance rate of 67.8 s ha−1 when no targets were detected. The maximum target acquisition rate for the HBT platform was estimated at 143 targets hr−1. An average mortality factor of 0.542 was derived from the product of detection efficacy (0.560) and operational treatment efficacy (0.972) in overlapping buffer areas generated from repeated flight segments (n  =  5). This population reduction value was used in simulation models to estimate the expected costs for one- and multi-year satellite population control strategies for qualifying options in cost optimization and risk aversion. This is a first report on the performance of an HBT helicopter platform demonstrating the capability for immediate, rapid-response control of new satellite plant detections, while conducting aerial surveillance of incipient miconia populations.

Management Implications

Herbicide Ballistic Technology (HBT) is a novel application technique designed to deliver encapsulated herbicide projectiles with long-range accuracy and precision. We report on the performance of an HBT platform providing immediate control of miconia (Miconia calvescens DC.) satellite plants, detected while conducting helicopter surveillance calibrations in Hawaii's remote watersheds. Flight calibrations (n  =  13) generated efficiency parameters related to the functionality of the platform. Plant target density was a significant variable for determining search efficiency (min ha−1), target acquisition rate (plants hr−1) and herbicide use (g ae ha−1). The product of detection efficacy and treatment efficacy estimated population mortality (i.e. reduction) as another operational parameter used in simulation models to project feasibility and expected cost of different population reduction strategies based on cost optimization and risk aversion. This research is critical to our technology transfer program that includes development of the standard operating procedure for safe use of the HBT platform, which has been approved by the Pacific Cooperative Studies Unit, University of Hawaii and approval by the Hawaii Department of Agriculture for a FIFRA Section 24c Special Local Needs registration for HBT-G4U200 with Garlon® 4 Ultra (EPA SLN Reg. No. HI-120001), with miconia listed as a target species.

Article Citation 

James J. K. Leary, Jeremy Gooding, John Chapman, Adam Radford, Brooke Mahnken, and Linda J. Cox  2013 Invasive Plant Science and Management: April-June, Vol. 6, No. 2, pp. 292-303.