Weed management: a need for ecological approaches - Ecological Management of Agricultural Weeds - page 8

direct-seeding techniques in place of transplanting, as in the case of rice
(Naylor, 1994).
Public and private institutions also play an important role in promoting
herbicide use. In developing countries, herbicide use is encouraged by
national and international organizations that provide technical advice and
loans to farmers (Alstrom, 1990, p. 169; Pretty, 1995, pp. 26-57) and by
government subsidies for herbicides and other pesticides, which lower their
cost to farmers (Repetto, 1985). Throughout the world, advertising empha-
sizes chemical solutions to weed problems. Agrichemical companies spent an
estimated $32 million for herbicide advertising in printed media in the USA
in 1994 (Benbrook, 1996, p. 165), and herbicide advertisements on radio and
television are also common.
Aconcentration of scientific research upon herbicides has strongly contrib-
uted to their importance as weed management tools in both industrialized
and developing countries (Alstrom, 1990, pp. 162-5; Wyse, 1992). Abernathy
& Bridges (1994) and Benbrook (1996, p. 163) surveyed weed science publica-
tions cited in Weed Abstracts and the Agricola database between 1970 and 1994
and reported that more than two-thirds of the articles focused on various
aspects of herbicides and their application. Although some research focused
on weed biology and ecology, only a small fraction of articles addressed com-
ponents of alternative weed management strategies, such as tillage, cultiva-
tion, crop rotation, cover crops, mulches, and biological control.
Technical and social factors that favor the dominance of herbicides over
other approaches for weed management are discussed in more detail in
Chapter 11. Here we will review some of the unintended impacts of herbicide
use that are leading a growing number of farmers, scientists, and policy
makers to seek alternatives to heavy reliance on herbicide technology.
Unintended impacts of herbicide use
Herbicide resistance in weeds and herbicide product
development
Reappraisal of herbicide technology has been driven, in part, by the
detection of herbicide resistance in a growing number of weed species.
Herbicide resistance is an evolved condition whereby exposure of a weed pop-
ulation to a herbicide leads to a predominance of genotypes that can survive
and grow when treated with herbicide concentrations that are normally fatal
in untreated populations. Before 1980, herbicide resistance was observed in
only a few weed species and was generally limited to triazine compounds