A COMPUTABLE ECONOMIC THRESHOLD MODEL FOR WEEDS IN FIELD CROPS WITH MULTIPLE PESTS, QUALITY EFFECTS, AND AN UNCERTAIN SPRAYING PERIOD LENGTH

A model is developed to determine the minimum weed population where a decision to apply a postmergence herbicide would be profitable. The economic threshold model accounts for changing economic conditions, the effect of weeds on crop quality, the effect of multiple weed species on yield and quality, and uncertainty about spraying period length. The model is uncomplicated enough for microcomputer or programmable calculator applications. An example of weed threshold calculations for round white potatoes is given.