James Leary isn’t your typical herbicide applicator. Dr. Leary is an invasive weed management Extension specialist with the College of Tropical Agriculture and Human Resources at the University of Hawai‘i at Mānoa. The invasive plants Leary works to control aren’t infiltrating a right-of-way or invading a roadside. They are invading tropical rainforests. Yet the lessons he has learned and the innovative techniques he has developed just might be applicable in more traditional vegetation management environments.
Living and working among tropical rainforests on the Hawai‘ian island of Maui, Leary is leading collaborative efforts to protect the tropical rainforests of Maui’s watersheds — one of the most pristine native ecosystems on the Hawai‘ian Islands. Here, Miconia and, to a lesser extent, strawberry guava, two non-native and very invasive plants, infest nearly all vertical mountainsides. Their growth threatens to work up slopes and choke out the all-important watersheds. These watersheds are critical to the viability of the island and essential to rare and endangered birds and plants that call these rainforests home.
Miconia’s spread spawns partnership
The introduction of Miconia to Hawai‘i can be traced back to 1961, when it was planted as an ornamental on the island of O’ahu. From there, it was planted in other places and continued its spread to all the other Hawai‘ian islands, including Kaua‘i and Maui. The plant is native to Central and South America and was prized by botanical gardens, which led to its use as an ornamental. Now, Miconia is considered one of the most highly invasive, destructive plants in the Pacific islands, having already spread to nearly 20,000 acres across the East Maui watershed alone.
In 1991, efforts to eradicate Miconia started in earnest as it threatened critical watersheds. But, by then, the problem had become more widespread than was initially believed. This realization resulted in public and private organizations partnering in an aggressive eradication effort.
Today, this partnership includes the East Maui Watershed Partnership, the Maui Invasive Species Committee (formerly the Melastome Action Committee), Haleakalā National Park, the University of Hawai‘i at Mānoa, Maui County, the Hawai‘i Department of Land and Natural Resources and The Nature Conservancy.
Herbicides (particularly Garlon 4 Ultra* specialty herbicide) have proven effective in controlling Miconia, but its growth on vertical cliffs makes traditional herbicide application techniques impossible. After joining the partnership in 2009, Leary began developing a technique that’s leveling the playing field against this challenging invasive plant.
“Helicopters were being used for surveillance and detection of infestations in larger areas and more difficult terrain,” said Leary. “But helicopter flight time is expensive, and using it solely for finding the plants that needed treatment wasn’t efficient.”
So Leary developed a unique application technique that allows for finding and treating Miconia in one flight. It’s called Herbicide Ballistic Technology (HBT).
HBT comes to the rescue
HBT is a method for applying herbicides by using paintball guns that are pneumatically powered by compressed air to propel herbicide-filled paintballs at high speeds over long distances. With HBT, the paintball guns shoot gel cap paintballs filled with a premixed herbicide solution. Each 0.68-caliber paintball is filled with 2.6 milliliters of Garlon 4 Ultra.
“It took a while to find a paintball manufacturer that was willing to listen to me when I told them I wanted to put herbicide into their paintballs,” said Leary. “When I did find one, it still took some convincing. But they took a chance and developed the first herbicide gel cap paintball. We found Garlon 4 Ultra very effective in controlling Miconia. Garlon 4 Ultra also was very compatible with the gelatin encapsulation process, because, unlike water-based herbicides, it did not compromise the integrity of the capsule.”
The manufacturer, Nelson Paint Company, based in Kingsford, Michigan, worked with Dow AgroSciences to develop the herbicide-infused paintball. With that in hand, the next step was successfully lobbying the U.S. Environmental Protection Agency for special local needs registration for Hawai‘i for HBT-G4U200 with Garlon 4 Ultra. Full-scale operations using HBT on Miconia began in 2012.
Operations seek and destroy
When you combine a Hughes 500 helicopter outfitted with an HBT platform to target vegetation, the operation becomes very similar to a military search-and-destroy mission. “We are hunting for these plants in order to kill them,” said Leary. Leary contracts with a local Maui helicopter service for conducting what are classified as low-level utility flights.
With year-round growth of the target species, they are currently conducting operations every month. A typical flight is up to two hours, with 70 percent of the time dedicated to surveillance, but if conditions are ideal, they might land and refuel and reload and return for another run. On a typical run, Leary or other certified applicators are seated directly behind the pilot, with a spotter sitting in the co-pilot seat.
Once airborne, Leary works in tandem with his pilot and spotter. The three-person crew is able to search one acre in just less than 30 seconds. If Miconia is found, it takes an additional 30 seconds to treat the plant.
“We’ve been fortunate enough to be working with the same group of pilots for a while now, and they’ve become a real asset to the operation,” said Leary. “Their ability to spot the plants that we need to treat, and then to get us into position to make the application, is critically important.”
In the first year, Leary’s team of collaborators recorded a total of 17 HBT missions, for a total of 65 hours of flight time, resulting in effective control of 3,730 Miconia plants. To date (as of August 2014), they have conducted 55 missions effectively treating 10,028 Miconia plants, thereby protecting over 13,000 acres of watershed.
While the HBT operations are in the air, the spotter uses tablet devices equipped with GPS mapping to plot each application run. This is important data in monitoring timing and control levels, which is vital to planning future operations.
“It’s important that we are efficient when conducting operations,” said Leary. “We need to balance protecting as much area as possible with eliminating as many plants as possible.”
The results have been phenomenal. Control levels for treated plants are near 100 percent. And as evidenced by the drop in treated plants year over year, the spread of Miconia is slowing down. Continuing to treat new areas of infestation and removing mature plants will eventually result in depleting seedbank reserves.
Is this a treatment option for the future?
Utility operations already using helicopters to both scout and treat rights-of-way might one day view HBT as a logical step in remote areas needing targeted control.
The technique comes with many benefits, including having ready-made herbicide projectiles without the need to handle or mix herbicide in the field, the elimination of the need to have water available for foliar applications, and the ability for applicators to treat in the most remote areas, with very precise and effective applications.
And for the record, it’s not as though Leary is an avid paintballer who simply adapted his equipment to apply herbicides.
“I’d never played or shot a paintball gun before in my life,” said Leary. “But in trying to develop a viable way to treat these plants, it seemed like a technology that might be suited to what I was trying to do.”
Article provided by Dow AgroSciences.
* Garlon is a trademark of Dow Chemical Company (Dow) or an affiliated company of Dow. State restrictions on the sale and use of Garlon 4 Ultra apply. Consult the label before purchase or use for full details. Always read and follow label directions.