An analysis of the annual costs of weeds in seven winter crops across Australia demonstrated that the most important 15 weed species cause substantial annual costs in both financial and economic terms. Using survey data captured over the 1998-1999 growing season, the financial cost of these weeds in seven crops was estimated to be AU$1,182 million. The main components of this cost were herbicides (AU$571 million), the competitive effects of residual weeds (AU$380 million), and tillage (AU$206 million) while weed contamination of grain was a minor cost (AU$25 million). Across all regions, the most economically important weeds were annual ryegrass, wild oats, and wild radish, although there were regional differences in importance. An economic surplus analysis determined the annual economic cost of weeds in annual winter crops to be AU$1,279 million. This surplus loss represented 17% of the gross value of Australian grain and oilseed production in 1998-1999. Australian grain producers incurred a major loss, with a reduction in producer surplus of AU$1,047 million. Australian grain consumers had a large consumer surplus loss (AU$229 million), while international consumers suffered a small loss and international grain producers gained a small producer surplus from the higher grain prices.JEL classification: D60, Q11, Q16

Serrated tussock (Nassella trichotoma), P grass native to South America, has been B major economic problem in the rangelands of southeastern Australia since 1950. It currently infests 680,000 ha in southeastern New South Wales, drastically reducing animal production. Controlling serrated tussock was profitable in most situations favourable for pasture improvement but only marginally profitable or unprofitable in areas with low to moderate soil fertility/rainfall indices. Internal rates of return ranged between 49.1% and 7.5% and the benefit-cost ratios between 1.83:1 and 0.X8:1. Public intervention was considered to be necessary to expedite control in areas less favorable for pasture improvement. Public rates of return (273.1% to 132.7%) and benefit-cost ratios (32.3:1 to 11.2:l) to control were very high under a system of subsidized finance to private landholders. Various forms of potential public intervention were discussed.

The European rabbit is present in most Australian environments and causes economic loss in agricultural systems by reducing production and imposing control costs on producers and governments. Research into rabbit control has recognised the need for reliable benefit‐cost analysis to justify inputs into rabbit management. This paper provides estimates of the costs of rabbits in Australian temperate pasture systems and of the long‐term benefits of reducing rabbits by the introduction of rabbit haemorrhagic disease (RHD). Rabbits impose annual costs on wool producers in the temperate pasture areas of between 7.1 and 38.7 million Australian dollars (mA$) depending on their density. Controlling rabbits by RHD has the potential to generate substantial long‐term economic benefits by reducing grazing competition with sheep. Reducing rabbit costs by 25% generated 15‐year net present values (NPVs) between 18.4 and 97.3 mA$ at various pre‐RHD rabbit densities. A 50% reduction in rabbit costs increased the total NPVs between 36.9 and 202.4 mA$, virtually all of which was captured by temperate area wool producers. The corresponding benefit‐cost ratios were between 2.9:1 and 16.2:1 for a 25% rabbit reduction and 5.9:1 and32.4:l for a 50% reduction, where the total costs of the RHD program in the temperate pasture areas were incurred by the wool industry. The analysis provides guidelines for the economic evaluation of other pest problems in agricultural production systems.

Weeds reduce the livestock production from pastures and impose control costs on producers and governments. Economic assessments of pasture weed problems are required on and beyond the farm for planning private and public weed control. This requirement has several dimensions that can be used to demonstrate the economic effect of weeds and encourage weed control by the private and public sectors. This paper discusses the economic problems of pasture weeds and the procedures for multi-level economic assessments with a major pasture weed in Australia as an example, and demonstrates the important private and social economic benefits from controlling this weed.

A recent analysis indicated that the direct financial cost of weeds to Australia's winter grain sector was approximately $A1.2bn in 1998-1999. Costs of this magnitude represent a large recurring productivity loss in an agricultural sector that is sufficient to impact significantly on regional economies. Using a multi-regional dynamic computable general equilibrium model, we simulate the general equilibrium effects of a hypothetical successful campaign to reduce the economic costs of weeds. We assume that an additional $50m of R&D spread over five years is targeted at reducing the additional costs and reduced yields arising from weeds in various broadacre crops. Following this R&D effort, one-tenth of the losses arising from weeds is temporarily eliminated, with a diminishing benefit in succeeding years. At the national level, there is a welfare increase of $700m in discounted net present value terms. The regions with relatively high concentrations of winter crops experience small temporary macroeconomic gains.