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Estimates of numbers of weed grass inflorescences in a single wheat field were made using 0·25 m2 quadrat counts. Precise estimates of mean field density could be achieved only at high sampling intensity, at least 18 locations (m2) ha-1.

Weed maps are typically produced from data sampled at discrete intervals on a regular grid. Errors are expected to occur as data are sampled at increasingly coarse scales.

Numerous studies have demonstrated the patchy distribution of weeds within fields. The majority of these studies have used discrete sampling, recording weed densities at the intersections of regular grids. In this study, Avena spp. seedlings were recorded on square grids at four sites.

This paper aims to provide guidance to ecologists with limited experience in spatial analysis to help in their choice of techniques. It uses examples to compare methods of spatial analysis for ecological field data.

Growers need affordable methods to sample weed populations to reduce herbicide use with site-specific weed management. Sampling programs and methods of developing sampling programs for integrated pest management are not sufficient for site-specific weed management because more and different information is needed to make treatment maps than simply estimate average pest density.

This paper reviews the literature concerning the spatial distribution of weeds; highlighting the limitations of our current sampling and analytical methodologies, and suggesting how these inadequacies can be addressed.

The ability to manage weed infestations in a spatially precise manner requires efficient and accurate methods of mapping weed distributions. A study was conducted to compare four different ground-based methods for collecting georeferenced information on infestations of Avena sterilis in winter wheat and barley.