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Invertebrates--Effect of pesticides on; Vernal pools; Mosquitoes--Control


Three temporary vernal wetlands on the Bayport Wildlife Management Area in eastern Washington County, Minnesota, were divided by sandbag barrier into treatment and control areas. Designated areas were treated with Altosid® SR-10 briquets at standard mosquito control rates. Invertebrate populations were monitored weekly using net sweeps, column samples, and ocular estimates.

The development of Eubranchtpus bundyi, Lyncerus sp, and Daphnia sp., the three major components of the invertebrate fauna, was delayed by as much as one week in site 47. Similar developmental lags were noted for E. bundyi populations in the treated portions of sites 6 and 32. Delay of maturation was expressed in greater longevity and higher male to female sex ratios for treated populations of E. bundyi. Daphnia sp., population growth was also retarded by treatment, with a concurrent lag in ephippium (resting egg) formation. Delay in the development or sexual maturity of vernal faunas could impact those faunas and the wildlife that are dependent on them as seasonal dietary protein resources.

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