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In the United States, Nebraska has the third highest incidence of human West Nile virus (WNV). Since WNV was first detected in the state in 2002, 3,422 confirmed cases and 57 deaths have been reported. Irrigated agro-ecosystems, which have been associated with elevated WNV incidences in other states, are prevalent in Nebraska. The objectives of this investigation were to 1) characterize mosquito abundance and diversity in irrigated agro-ecosystems, and 2) evaluate associations of two primary vectors of WNV, Culex tarsalis and Culex pipiens, with irrigation methods (sprinkler vs. surface) and crop type (corn vs. soybean). Investigations were conducted at South Central Agricultural Laboratory (SCAL) and privately owned operations in Clay County, Nebraska.
A total of 349,847 mosquitoes were collected during 2012 and 2013, representing 14 species and seven genera. The three most abundant species were Aedes vexans (53.7%), Culex tarsalis (37.6%) and Culex pipiens (2.4%). Other mosquitoes included Anopheles punctipennis, Anopheles quadrimaculatus, Coquillettidia perturbans, Culiseta impatiens, Culiseta inornata, Ochlerotatus dorsalis, Ochlerotatus sollicitans, Ochlerotatus trivittatus, Psorophora ciliata , Psorophora columbiae, and Psorophora cyanescens.
At SCAL, Culex abundance did not significantly differ between crop (P=0.11) or irrigation (P=0.98) types, but did significantly differ between years (P=Culex mosquito abundance in corn fields in 2012 (mean= 52.45, P=0.0053); center pivot irrigated corn fields collected 52.5% fewer Culex mosquitoes than furrow surface irrigated corn fields. Field management practice differences, proximity of alternative larval developmental sites to study areas, and drought conditions during the study period potentially affected mosquito diversity and abundance. Continued surveillance during years with average or above average precipitation is recommended to adequately characterize adult mosquito populations in these systems.
Advisor: Roberto Cortiñas