Relative humidity and activity patterns of Ixodes scapularis (Acari: Ixodidae)

Journal of Medical Entomology
By: , and 

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Abstract

Laboratory studies have shown clear relationships between relative humidity (RH) and the activity and survival of Ixodes scapularis Say (blacklegged tick). However, field studies have produced conflicting results. We examined this relationship using weekly tick count totals and hourly RH observations at three field sites, stratified by latitude, within the state of Rhode Island. Records of nymphal tick abundance were compared with several RH-related variables (e.g., RH at time of sampling and mean weekly daytime RH). In total, 825 nymphs were sampled in 2009, a year of greater precipitation, with a weighted average leaf litter RH recorded at time of sampling of 85.22%. Alternatively, 649 nymphs were collected in 2010, a year of relatively low precipitation, and a weighted average RH recorded at time of sampling was 75.51%. Negative binomial regression analysis of tick count totals identified cumulative hours <82% RH threshold as a significant factor observed in both years (2009: P = 0.0037; 2010: P < 0.0001). Mean weekly daytime RH did not significantly predict tick activity in either year. However, mean weekly daytime RH recorded with 1-wk lag before sample date was a significant variable (P = 0.0016) in 2010. These results suggest a lag effect between moisture availability and patterns of tick activity and abundance. Differences in the relative importance of each RH variable between years may have been due to abnormally wet summer conditions in 2009.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Relative humidity and activity patterns of Ixodes scapularis (Acari: Ixodidae)
Series title Journal of Medical Entomology
DOI 10.1603/ME13186
Volume 51
Issue 4
Year Published 2014
Language English
Publisher Entomological Society of America
Contributing office(s) Patuxent Wildlife Research Center
Description 8 p.
First page 769
Last page 776
Country United States
State Rhode Island
City Charlestown, Exeter, Scituate
Other Geospatial Arcadia Management Area, Burlingame Management Area, Scituate Reservoir
Online Only (Y/N) N
Additional Online Files (Y/N) N