Aquatic insect responses to Bacillusthuringiensis var. kurstaki in a forest stream

A section of forest stream was treated with Bacillusthuringiensis Berliner var. kurstaki (B.t.k.) at 10 × the expected environmental concentration (200 IU/mL) to determine effects on the macroinvertebrate community. Invertebrate drift density increased slightly (approximately 2-fold over pre-treatment densities), but only during the 0.5-h application and only at the site 10 m below the application point. There were no significant changes in taxonomic richness of benthic invertebrates after the application, but there were short-term alterations in community structure at the treated site after the application, as measured by the χ2 dissimilarity index. In 11 of 12 benthic taxa for which there were sufficient data, changes in abundance after the application were not significant compared with changes in abundance at the reference site. The stonefly Leuctratenuis (Pictet) was significantly reduced (~70%) at the treated site 4 d after the application, and abundance of this stonefly remained considerably lower, ...