A juvenoid insect growth regulator, pyriproxyfen (Nylar or Sumilarv), in a 10% emulsifiable concentrate (10 EC) and a granular (3% sand granules) formulation was evaluated for efficacy against natural populations of chironomid midges in man-made ponds in central Florida. Both formulations at 0.05 kg AI/ha induced complete suppression of adult midge emergence for 1 wk. At 0.2 kg AI/ha, emergence of adult midges completely ceased for 2 and 5 wk with the EC and the granules, respectively. The EC formulation was not effective beyond 2 wk, but the granules at both treatment rates reduced midge emergence by 81-100% for 9 wk posttreatment. The differences in suppression of adult midge emergence between the 2 formulations and times posttreatment were both highly significant (P < 0.01). No significant difference (P > 0.05) was found between the posttreatment percent inhibition of midge emergence caused by the lower and the higher rates of the granular formulation. Some reductions of midge larvae occurred in the ponds receiving the higher rate of the 2 formulations, but these reductions were statistically not significant.