LOG-LOGISTIC ANALYSIS OF HERBICIDE DOSE-RESPONSE RELATIONSHIPS

Dose-response studies are an important tool in weed science. The use o f such studies has become especially prevalent following the widesprea d development of herbicide resistant weeds. In the past, analyses of d ose-response studies have utilized various types of transformations an d equations which can be validated with several statistical techniques . Most dose-response analysis methods 1) do not accurately describe da ta at the extremes of doses and 2) do not provide a proper statistical test for the difference(s) between two or more dose-response curves, Consequently, results of dose-response studies are analyzed and report ed in a great variety of ways, and comparison of results among various researchers is not possible, The objective of this paper is to review the principles involved in dose-response research and explain the log -logistic analysis of herbicide dose-response relationships. In this p aper the log-logistic model is illustrated using a nonlinear computer analysis of experimental data. The log-logistic model is an appropriat e method for analyzing most dose-response studies, This model has been used widely and successfully in weed science for many years in Europe . The log-logistic model possesses several clear advantages over other analysis methods and the authors suggest that it should be widely ado pted as a standard herbicide dose-response analysis method.