What started out as a “rocky” relationship between the Salt Lake City Mosquito Abatement District and the Kennecott Inland Sea Shorebird Reserve (home and nesting place to more than 250 species of birds) has evolved into a successful public/private partnership, explains Dr. Sam Dickson, District Manager. Because the district covers the environmentally significant bird reserve, the challenge facing Dr. Dickson was how to treat the man-made wetlands on the reserve without disturbing the birds and their nests.
Created by Kennecott Utah Copper in 1997 to replace land affected by mining, the reserve covers more than 3,600 acres. In addition to being a refuge for birds, the area is an important educational and scientific resource for Kennecott employees, birding groups, schools and university research teams.
When the reserve first opened, the district was not allowed to treat the wetlands. To precipitate a dialog, Dr. Dickson sent a team into the area, which forced the issue and started the conversation.
“I didn’t want to, but I had to treat the lands. After knocking heads a bit, we both backed down and started talking more. We get along pretty well now.”
“Each week, the reserve must document the number of birds living there. The staff who do the counting really love birds, and any time we’re out on their area, we want to coordinate so we don’t disturb birds and affect the count.”
Dr. Dickson was looking for a solution that would satisfy the reserve superintendents and allow him to treat the wetlands. Always willing to explore new solutions, he agreed to test MetaLarv® Mosquito Growth Regulator, Valent BioSciences Corporation’s (VBC) new biorational pre-hatch insecticide.
“The test gave the district an effective and safe solution because we could meet Kennecott’s needs and ours and avoid going in and walking around stepping on eggs or nests,” Dr. Dickson adds.
“We asked the reserve manager if we could have some lakes for a trial with a long-lasting mosquito larvicide product that could potentially be applied in the springtime. That way, we wouldn’t have to disturb the birds during the nesting period. The manager was happy with that idea. It looked like a win-win.”
As with all field trials, conditions didn’t exactly match expectations. Some of the lakes in the test area got flooded, some didn’t get reflooded. Where there was flooding and reflooding, excellent results were observed — about six weeks of control, according to Dr. Dickson.
“MetaLarv® is very different from other Valent BioSciences products because it doesn’t cause immediately visible larval mortality. It’s a mosquito growth regulator, meaning the mosquito larvae don’t become viable adults,” adds Stephanie Whitman, Senior Public Health Products Specialist. “Areas pre-treated with the product are expected to be free of mosquitoes for up to 42 days. Salt Lake saw 50 days of suppression.” The mosquito species prevalent in the area is Aedes dorsalis, also called Ochlerotatus dorsalis.
District biologist Banu Kesavaraju explains how the test was conducted: “We started the field test during the last week of April. We applied MetaLarv® with backpack sprayers. It took about three or four hours to lay down the product. Because Kennecott is a bird reserve, the caretakers can control the flooding. There are several lakes and the caretakers decide what areas can be flooded, depending on the birds and nests. This is what we wanted to test — could we apply one single product that would withstand the reflooding?”
After they applied MetaLarv® on May 3, the team began sampling the sites weekly for pupae. Once they had gathered 50 pupae and returned them to the lab, they waited a week to see if mosquitoes emerged. “Typically, most pupae emerge as adults in two days. But if they are affected by the product, they won’t come out or they will die in a few days,” Kesavaraju continues.
On June 22 (around the 50th day), the final dip was performed. All the pupae had died, showing 100 percent suppression. When the next flooding occurred on August 8, they collected pupae and saw some reduction in
Kesavaraju notes that he would have preferred to have reflooded the fields more frequently, but nature doesn’t always cooperate. Because this year was extremely hot, the water at some of the sites evaporated quickly and they were not reflooded. “We had reflooding in only two sites. We would have preferred if they had flooded all seven sites, because the results would have been more comprehensive.”
“Operationally, we may have rain. We may have drought. Putting out a longer-lasting product may save on manpower, but in the long run it may hurt you if you have unusual environmental conditions. So I’d rather apply product every week. MetaLarv® was not used in any other parts of the district. But in this particular case, we wanted to limit the time we were in there so we didn’t disturb the birds,” Dr. Dickson adds.
Previously, the district relied on aerial applications of VectoBac® and VectoLex® Biological Larvicides. “In deciding whether to use MetaLarv® in other parts of the district, I need to make sure I get the best bang for my dollar or have a unique circumstance like the bird preserve. From what we saw this year, MetaLarv® is something we can use in the future in this area and keep everyone happy. It’s another tool that I can now use. It adds to my tool chest.”
The test also gave the Salt Lake City District the opportunity to share their successes with other districts across the country. Kesavaraju presented a paper on their results at the Northwest Mosquito and Vector Control Association meeting in West Yellowstone, Montana. Dr. Dickson believes that other districts with similar issues may benefit from his district’s experience.
To learn more about MetaLarv®, visit us at www.publichealth.valentbiosciences.com/products/metalarv.