A MATHEMATICAL-MODELING APPROACH TO THE STUDY OF THE ECONOMICS OF CONTROLLING RUMEX-OBTUSIFOLIUS IN GRASSLAND

Synthesizing data from several sources, a simplified mathematical model of dock (R. obtusifolius) reproduction, growth and competition with grass was constructed. Using the model, an attempt was made to study the short- and long-term economic implications of controlling dock infestation in a grassland conservation system by use of the herbicide asulam. The sensitivity of the results was tested in respect of assumptions about the efficacy of asulam in controlling docks and the economic values attached to grass and dock dry-matter production. Given the large number of assumptions necessitated by the limited availability of data and in the absence of any means of validating the model, extreme care is needed in interpreting the results. While the model cannot be used to derive practical recommendations it can and does provide some useful insights into herbicide control of docks. Confident economic predictions of the value of controlling docks in grassland await further experimental work on the population dynamics of docks, the factors influencing the effectiveness of herbicides and the nutritive value of docks.