Pilot Study of Sublethal Effects on Fish of Pesticides Currently Used and Proposed for Use on Maine Blueberries

Blueberry pesticides have been detected consistently in some Down East Maine rivers, yet little is known about the sublethal effects of these pesticides on fish early life stages. The Maine blueberry industry is proposing to replace the insecticide ImidanTM (active ingredient phosmet) and the herbicide VelparTM (active ingredient hexazinone), two of the pesticides found in these rivers, with candidate alternatives SpinTor TM (active ingredient spinosad) and Callistso TM (active ingredient mesotrione). Our objective is to evaluate potential sublethal effects of these four formulations before the industry adopts the two candidate alternatives. We exposed zebrafish (Danio rerio) early life stages, from fertilization through larval swim-up, to a range of pesticide concentrations and evaluated their response relative to untreated controls. In this report we provide preliminary data on immune function as well as on parameters in addition to those originally proposed: development and performance fitness. We also provide information on our progress towards optimizing chemical protocols for analyzing the concentration of active ingredient in each of our formulation dosing solutions, another new parameter we added to those originally proposed. Preliminary results indicate that at environmentally realistic concentrations, these pesticides may have no significant effect on innate immunity, development rate or behavior (spontaneous swimming), however further replication is needed to confirm these initial findings. We have also observed some degree of developmental abnormalities in both pesticide-treated and control zebrafish embryos; however, additional replication is underway to determine if these groups differ significantly.