Toxicity of methoprene to all stages of the salt marsh copepod, Apocyclops spartinus (Cyclopoida).

The toxicity of methoprene to the salt marsh copepod Apocyclops spartinus was evaluated and compared with sensitivity of mosquito larvae. All stages of the life cycle were tested at concentrations ranging from 0.1 to 10.0 ppm. Eggs and the earliest hatched stages, nauplius I-III were most sensitive to methoprene, with little mortality seen in the later stages. Toxic effects were manifested as death, or failure of eggs to hatch, however, no extensions of the life cycle were observed. In general the copepods were resistant at concentrations of methoprene used to control mosquitoes. Early nauplii, however, did show some mortalities to methoprene concentrations near the lower margins of mosquito susceptibility. This might lead to transient decreases in copepod population growth rates, but not necessarily to decreases in their standing populations.