- Trial, Joan Garner
University of Maine
Sampling in six streams which had been evaluated in 1976 for the impact of Sevin-4-oil on aquatic insects was continued in 1977. Standing crop was sampled in June and August. Included in the study were two streams treated in 1975 and 1976, two streams treated only in 1976 and two untreated streams. The objectives of the study were to determine if recolonization of Plecoptera occurred in streams from which the order had been eliminated by the insecticide and if long term changes in the communities of Trichoptera, Ephemeroptera and Diptera occurred as a result of insecticide application.
1977 Plecoptera collections from treated streams were not similar in generic composition to prespray collections for the same streams. However, the numbers of individuals and taxa were not significantly different in May 1976 and August 1977 for streams treated in 1976 only. Plecoptera collections from one stream treated in 1975 and 1976 showed recolonization by some genera. Recovery of Ephemeroptera populations had occurred except for the complete loss of Hexagenia from collections on one stream. Revocery of Diptera and Trichoptera populations had occurred with the exception of Tipulidae. This family was low in number of individuals and taxa for all of 1977 in two treated streams, one from each treatment group.