Ratio Estimation Fusiform Rust Incidence in Southern Pine Plantations

Incidence of infection with Cronartium fusiforme was determined by examining each tree in eighteen 3- to 15-year-old plantations of slash or loblolly pine of 9 to 11 acres each. With these data, empirical sampling trials were carried out, with the individual rows of trees as the basic sampling unit, to determine the biases involved in various estimates of the proportion of infected trees and of the variances of these estimates. For most purposes the bias in estimating proportions of infection would be negligible even with sample sizes as small as three rows per plantation; whereas, for samples of this size, bias in the estimated variance might be as much as 13 percent. Forest Sci. 17:135-142.