Lake Roosevelt National Recreation Area Implements Interim Mosquito Measures

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Date: April 24, 2017
Contact: Brandon Cadwell, 509-754-7866

While the National Park Service (NPS) considers mosquitoes a natural component of the ecosystem, we also recognize that mosquitoes can pose a risk to human and wildlife health. Following the recommendations of the Centers for Disease Control (CDC) and NPS guidelines, Lake Roosevelt staff has developed an interim measure to deal with mosquito populations while we work with the public to develop and implement an integrated pest management plan. The interim measures include the following components:

  1. Surveillance (monitoring levels of mosquito activity, and where virus transmission is occurring),
  2. Reduction of mosquito breeding sites,
  3. Possible control of both mosquito larvae and adult mosquitoes, including use of pesticides and biological methods, as indicated to be necessary by surveillance results, and
  4. Community outreach and public education: (
The CDC website states, “Control measures, including the decision to use chemical adulticides (pesticides to kill adult mosquitoes) should be based on surveillance data and the risk of human disease.” For the past two summers the NPS, in conjunction with the Washington State Department of Health, has been collecting and monitoring mosquitoes in the Kettle Falls area for West Nile Virus (WNV) to assess disease risk. Part of this surveillance is to determine the species and mosquito population levels in our area. Through this monitoring WNV was identified once in Stevens County during the summer of 2016. The NPS will continue to monitor population levels and disease risk through surveillance.
With this in mind, the NPS is working on the second aspect in our interim management measures. The Kettle Falls area has a large amount of invasive plant species, specifically black locust trees and several varieties of non-native grasses.  Through the interim measures, staff is working to reduce the number of the black locust trees in this area. In addition, the NPS is planning to reduce more mosquito habitat using prescribed fire in 2018 to manage invasive grasses. Finally, the NPS may also be reducing irrigation in several areas to reduce mosquito habitat. Proactively managing potential mosquito habitat creates a healthier environment and protects more beneficial insects and animals that feed on mosquitoes, such as birds and bats.
The third aspect of the NPS protocol is the possible use of larvicide when disease carrying mosquitoes are identified and pose a significant health threat. The NPS will need to apply to the state of Washington for a permit to use a larvicide when needed. Also, the NPS is prepared to test the use of mosquito traps in areas of high visitor use.
According to the Washington State Department of Health, Zika virus is not a threat in our state due to low wintertime temperatures. West Nile Virus has been found throughout the state for over 10 years in various and changing locations. While mosquito eradication is simply not feasible and not the goal of the NPS efforts, the measures are aimed at managing population sizes. 
With these items in mind, the NPS will continue to ask our neighbors and visitors to apply the following CDC recommendation, “You can reduce your risk of being infected with WNV by using insect repellent and wearing protective clothing to prevent mosquito bites.”
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Last updated: April 24, 2017

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Lake Roosevelt National Recreation Area
1008 Crest Drive

Coulee Dam, WA 99116



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