HERB: Decision Model for Postemergence Weed Control in Soybean

To efficiently use postemergence herbicides, decision makers must determine when weed populations exceed economic treatment thresholds. An interactive microcomputer program named HERB has been developed to help evaluate potential crop damage from multi‐species weed complexes in soybean [ Glycine max (L.) Merr.] and determine the appropriate course of action. Seventy‐six weed species were rated on a scale of zero to 10 according to their competitiveness with soybean. Potential yield loss is estimated from these rankings, the number of weeds of each species present in the field, and expected weed‐free yield. The recommendation whether to apply a herbicide and, if so, which one, is based on herbicide cost and efficacies under different conditions and expected soybean selling price. Alternative herbicide choices are ranked according to expected net return. HERB is intended to provide the latest research information in an organized and easily usable format. The approach should be applicable to other crops and pests.