USE OF STREAM WIDTH FOR DETERMINING THE DOSAGE RATES OF BACILLUS-THURINGIENSIS VAR ISRAELENSIS FOR LARVAL BLACK FLY (DIPTERA, SIMULIIDAE) CONTROL

Data from several operational black Ap abatement programs using Bacill us thuringiensis var. israelensis (B.t.i.) in New York State's Adirond ack Mountains were analyzed to determine what the concentration oi for mulation in the stream might have been if application rates were deter mined by a stream's width rather than its discharge. There was a high correlation (\R\ = 0.87) between discharge and width measured at 315 t reatment sites. Had the applications been based upon the stream width, 96% of the actual concentrations in the streams would have been withi n plus or minus a factor of 5 and none exceeding a Factor of 10, a ran ge in which B.t.i. remains environmentally safe and effective.