The Crested Butte News Serving the Gunnison Valley since 1999
Seeking an end to aerial spraying
The aerial application of a pesticide to kill mosquitoes in Gunnison County has been called into question by local fishermen and wildlife experts.
Last June, the annual practice was followed by a noticeable die-off in aquatic insects, including the stonefly, Claassenia sabulosa, which is considered an indicator of ecosystem health, and a good omen for fishermen, as they lure fish to the surface to feed.
Yet many local anglers believe that last summer’s die-off, while more noticeable than usual, was not an anomaly. They say the longtime practice of spraying a Permethrin-based pesticide from airplanes is adversely affecting area waters. They gathered en force when Colorado Mosquito Control (CMC) office manager Chris Kruthaupt gave his annual report to the Board of County Commissioners on December 11. They asked for a review of the pesticide and the policy, and it was likely just the beginning of a more in-depth conversation.
Banner year for mosquitoes
According to Kruthaupt, it is reasonable to connect last summer’s insect kill with the aerial spraying. What many experts predicted as a light mosquito season turned out to be fairly intense in spite of draught conditions. “It took us by surprise and took a lot of people by surprise in the state,” Kruthaupt said.
Locally, he attributes the size of the mosquito population to high temperatures and efficient irrigation practices. CMC followed standard protocol by targeting mosquito larvae first, applying about 800 pounds of a bacteria that targets larvae to more than 1,200 sites in the mosquito control area.
“We did a pretty good job controlling with bio-means until the middle of June,” Kruthaupt said. At that point, some of the mitigation practices became less compatible with irrigation practices. Staff had to stop using ATVs and travel by foot to apply the bacteria—that slowed the entire process until late June, when CMC hired an operator to spray a pesticide by plane.
“That’s typically when the mosquito population peaks as a whole, later in June, and we time that with the Forth of July holiday to provide a level of comfort as well for residents and also for guests,” Kruthaupt said.
He added that CMC typically sprays between 12,000 and 14,000 acres using a pesticide whose active ingredient is Permethrin. The pilot followed standard setbacks of 300 feet from water bodies, but Kruthaupt acknowledged that the insect kill was “pretty timely with the application” and suggested that it would be reasonable to suspect spraying as a root cause.
“We’d like to find a common ground to continue to do this…,” Kruthaupt said. “To me it was an outlier because of the remarkable changes in the flow regime of the river. We were looking at 300 cubic feet per second versus several thousand, which was the historical average.”
But that wasn’t enough for some members of the public, who sought more detailed information.
New pilot could have been a factor
Anthony Poponi, Gunnison resident and outgoing director of the Coal Creek Watershed Coalition, said, “I just wanted to try to tease out some other factors that could have caused this sort of die-off… Are we looking at a wind issue or an inversion or anything like that?”
“Any one of those could have [played a role],” Kruthaupt said. “A bit of a gust of wind can cause a drift of 300 feet, which we know is possible when we’re talking about 15-micron drops of this material,” he said. The chemical is sprayed in aerosol form so it will have uniform drift, but studies have shown that under the right conditions it can drift 1,000 feet.
Kruthaupt explained that an onboard weather station showed some slight winds the evening the pilot sprayed, and there may have also been some temperature inversions. Using a new pilot may have played a role as well.
In the past, CMC hired an operator from Montrose who flew about 150 feet above the ground at 120 miles per hour. He no longer performs vector control work, however, and the new pilot flies a different aircraft 200 feet above the ground at 150 miles per hour.
“I suspect the fact that we sprayed in the evening and had a new operator may have exacerbated the problem,” Kruthaupt said.
And while that may be, many of the anglers present at the meeting suggested that the stonefly die-off is an annual problem. They asked for a careful review of the mosquito program’s policies.
Asking for careful review of chemicals
Mark Day of Almont Anglers said aquatic inspects die off almost every year the county sprays for mosquitoes. “This isn’t the first time it killed insects in the river and it won’t be the last,” he said.
“The warning label says do not apply this unless there’s humongous health concerns. This is not to be decided by the board, it’s to be decided by public health officials. If you can read the label, there would be no spraying. The label says don’t spray this over water,” Day continued.
Chris Madison, president of the local chapter of Trout Unlimited, echoed Day’s concerns. “The guys on the river are really in touch with the pulse of the river and the slight changes made each day,” he said. “Most guides, late in the season, fish the upper river… A lot of them think the green drake hatch is close to extinction on the lower part of the river.”
Commissioner Hap Channell took their concerns to heart, asking county staff, “Are we in violation? Has the pesticide been submitted for review?”
But according to Richard Stenson, the county’s environmental health specialist, the county falls under a state discharge permit. “There would not have been regulatory oversight by my office or the county unless we elected to have that responsibility,” he said.
And human health has been one of the primary drivers for spraying in the first place. The West Nile virus has been a problem in neighboring counties—20 cases, including two deaths, were reported in Montrose County in 2012, while 22 cases and one death were reported in Delta County. So far, Gunnison County has reported only two cases since 2004 and no deaths.
