Measuring the Local Distribution of Ribes

Abstract

Blister rust control, as is well known, consists of the destruction of the alternate hosts, currant and gooseberry plants (Ribes spp.), in and near stands of susceptible five-needle or white pines. The ribes population must be reduced to a very small figure in order to accomplish the protection of the pine. Making sure, either before or after eradication, that the ribes in a stand are so few as not to menace the pine involves systematically checking the stand and its environs. The checking procedure used in the Rocky Mountain and Pacific Coast States is described by Harris ('41). The checkers are usually required to cover either 4 per cent or 5 per cent of the land area under examination and to report the number and location of the ribes discovered. Considerable attention has recently been given to the problem of evaluating the sampling data obtained by 4 per cent, 5 per cent, and 8 per cent checks, respectively. Their significance involves three phases: (1) The reliability of the checking record as an estimate of the total ribes population on unit areas of various sizes; (2) determining how ac-