Comparison of dry ice-baited centers for disease control and New Jersey light traps for measuring mosquito abundance in California

Mosquito catch in New Jersy light traps (NJLTs) has been declining in recent years, compromising the sensitivity of the California mosquito monitoring program. Centers for Disease Control traps (CDCTs) operated without light and augmented with dry ice have been considered for replacement or augmentation. To provide information on comparative sensitivity and ability to measure abundance over time and space, catch of mosquitoes in NJLTs was compared to catch in CDCTs operated concurrently at 8-10 sites within the Coachella Valley, Kern, San Joaquin County, and Sacramento-Yolo Mosquito and Vector Control Districts. The CDCTs always collected more female mosquitoes than did NJLTs; however, differences in sensitivity varied markedly over time and space precluding the calculation of a universal conversion factor. Regressions of the catch of female Culex tarsalis in CDCTs as a function of catch in NJLTs within districts indicated that the slopes varied markedly, again precluding the derivation of a universal function. Therefore, we recommend that mosquito surveillance programs replace or supplement NJLTs with systematically operated CDCTs to enhance sampling sensitivity for females of most mosquito species. However, both trap types should be operated concurrently at several sites within each district to derive regression functions to convert historical relative abundance data from NJLTs to equivalent counts in CDCTs for retrospective analyses.