Delina Dority and Morgan Alexander Ford Advisor: Lusha Tronstad, WYNDD Does Mosquito Control Reduce the Aquatic Invertebrates in Spring Creek, Laramie, Wyoming? Delina Dority and Morgan Alexander Ford Advisor: Lusha Tronstad, WYNDD

West Nile Virus (WNV) West Nile Virus effects many western towns Laramie controls mosquitos to reduce the threat of WNV Spraying for mosquitos may have unintended consequences West Nile Virus effects many Western towns in the U.S. To help reduce the risk of infection many towns have increased

The Mosquito Life Cycle Discuss what life stages are targeted with mosquito control practices Most lay eggs in water Bti is the insecticide used to kill mosquitos in standing water where they live as larvae Live in standing water

Permethrin Regulations and Effects on Aquatic Ecosystems Many studies have shown that Permethrin is toxic to aquatic animals, mainly anything with gills 1970s the EPA required a 100 foot open-water buffer restriction for Permethrin application sites In 2006, the EPA removed the buffer restriction in an effort to control the spread of West Nile Virus in the United States

Permethrin Application in Laramie In Laramie, Wyoming mosquito abatement protocols are similar to those across the country. Bti is applied to still-water environments to control larval mosquitos, and Permethrin containing compounds are applied via ultra-low volume (ULV) foggers to residential areas throughout the summer. This includes areas adjacent to an important tributary of the Laramie River known as Spring Creek.” April/ May – September/ October (depending on mosquito detection) Ultra Low-Volume foggers Residential areas are treated on a rotating schedule Parks are treated Sunday- Thursday nights “We collected drift samples before, immediately after (~3-6 hours), and one day after (~28 hours) insecticide application. We measured a significant increase in abundance, biomass, and richness of drifting insects immediately after pesticide application. The increase in drifting invertebrates may have cascading effects on the ecosystem by altering resources available to fish and riparian birds. Understanding the unintended ecological impacts of pest control practices can lead to more effective and less detrimental management strategies.” Laramie Mosquito Control Program/West Nile Virus Plan: First adopted in 2003 Runs congruently with nuisance mosquito plan Bacillus thuringiensis israelensis (Bti) Permethrin and other insecticides Ultra-low volume fogger

Spring Creek Originates from a spring north of Grand Ave. (near Murdoch’s) City of Laramie protects spring Spring Creek exists entirely within City of Laramie

Spring Creek What’s so important about such a small stream? Supports year-round population of brown trout (~1000 fish per mile) Spawning habitat for trout from the Laramie river Provides habitat and food for riparian birds, mammals, and amphibians Several organizations are involved in habitat restoration on the Laramie River

What do we know? Morgan measured invertebrate drift immediate before spraying, immediate after spraying and 1 day after spraying. Discuss why invertebrates drift Measuring Invertebrate Drift Drift = downstream transport of invertebrates

Trends in Drift Samples The density and biomass of all aquatic invertebrates increased immediately following treatment of Permethrin. Spraying Up to 11x more invertebrate drifting immediately after spraying Permethrin 25th and 75th percentiles Box holds 50% of data

Hess Sampling Does mosquitoes control reduce the density and biomass of invertebrates living in Spring Creek?

Methods Collected Hess samples: Before spraying began in June After 2 months of spraying in August Sorted invertebrates Identified invertebrates under a dissecting microscope Measured length to calculate biomass

Invertebrate Density Density of all invertebrates was lower after permethrin spraying for 2 months (ind/m2) Before After

Invertebrate Biomass Biomass of all invertebrates was lower after permethrin spraying for 2 months (mg/m2) Before After

Density of non-insect decreased after spraying Before After (ind/m2) Density of non-insect decreased after spraying Density of insects increased after spraying

Biomass of non-insects was lower after spraying Before After Non-Insects Most Abundant Biomass of non-insects was lower after spraying Non-insects more abundant in Spring Creek Insect body size was smaller after spraying (early instars)

Annelids and crustaceans most abundant non-insects Before After (ind/m2) Annelids and crustaceans most abundant non-insects Densities decreased after 2 months of spraying

Before After (mg/m2) Biomass of non-insects decreased after 2 months of spraying, including Annelids

True flies tolerant of poor conditions Tolerant mayfly in the stream Before After (ind/m2) Densities of true flies and mayflies increased after 2 months of spraying True flies tolerant of poor conditions Tolerant mayfly in the stream

Fewer Invertebrates in Spring Creek Less food for fish Fewer adult insects emerging for birds to eat Fewer insects eating algae = greener stream Smaller insects after spraying may indicate that few insects are surviving to develop into adults Non-insects most abundant = sign of an impaired stream

What Does This Mean for Spring Creek? Permethrin applications near Spring Creek appear to be reducing non-target aquatic animals Re-evaluation of treatment practices to minimize impacts on Spring Creek animals while still effectively controlling mosquito populations may be in order

Acknowledgements Lusha Tronstad, Wyoming Natural Diversity Database Scott Seville, Wyoming INBRE Kieth Wardlaw, City of Laramie Mosquito Control Supervisor Tony Hoch, Laramie Rivers Conservation District Steve Gale, Wyoming Game and Fish Department Biodiversity Institute Wyoming Natural Diversity Database staff Mark Anderson, Wyoming Natural Diversity Database Christy Bell, Cody Bish, Tyler Dooley, Isaac Dority, Kyle Hack, Hunter McFarland, Oliver Wilmot, Aimee Wood