Effects of Diflubenzuron on Benthic Macroinvertebrates in Littoral Enclosures

Two applications of the insect growth regulator diflubenzuron were made to replicate littoral enclosures at nominal concentrations of 0.7, 2.5, 7.0, and 30 &mgr;g/L. Assessment of the effects of this insecticide on benthic macroinvertebrate community structure was accomplished by measuring changes in abundance and taxonomic richness. Chironomidae and Ephemeroptera were the most sensitive groups sampled, with no observed effect concentrations of 2.5 and 0.7 &mgr;g/L, respectively. No adverse effects were observed on Mollusca or Oligochaeta at any of the test concentrations. Taxonomic richness was noticably reduced at 7.0 and 30 &mgr;g/L on all post-application sampling dates, producing changes in community structure that persisted for >/=57 days.