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Abstract
Herbicide labels recommend sufficiently large doses to achieve high efficacy of weed
control under a range of environmental conditions. While users may not apply doses
greater than recommended they may apply less, but do so without quantitative
guidance. This paper explores long-run biological and economic outcomes of fixed
label doses and strategies keyed to density of weeds in Òbest fixed-doseÓ (BFD) and
Òbest efficacy-targetingÓ (BET) modes. Analysis based on 59 experiments in wheat
fields across southern Australia, from 1986 to 1995, indicate the latter strategies are
superior to maximum label rates in terms of (a) mean net present values of current and
future benefits and costs of weed management, expressed as Hamiltonians keyed to
weed seed banks, (b) mean current gross margins, and (c) lower overall herbicide use.
BFD have further practical advantages in simplicity and lower information
requirements for the user, BET in tailoring applications to specific field
environments.