Datura stramonium (jimsonweed)

As a weed in more than 100 countries, D. stramonium is considered by Holm et al. (1997) to be more widespread than even Cyperus rotundus which is ranked as the world's worst weed. Crop losses due to competition from D. stramonium depend on the crop and climatic conditions. Season-long competition resulted in 56% yield loss in cotton in the USA, but only 16% in the case of a more competitive soyabean crop (Oliver et al., 1991). Even sparse populations can be damaging with individual plants reducing the yield of soyabean plants growing within a distance of 1.2 m (Henry and Bauman, 1991). Reductions in the yield of irrigated maize by 56% due to season-long competition from D. stramonium have been reported in Spain by Torner et al. (1995). At a density of 3-11 plants per m², yields of directly-seeded tomatoes may be reduced by 26-71% (Monaco et al., 1981).D. stramonium serves as an alternate host for several pests and pathogens of Solanaceous crops; an extensive listing can be found in Weaver and Warrick (1984). Some of the more important include Manduca sexta, Phthorimaea operculella (tobacco leaf miner in Australia, North America and South Africa), species of Alternaria and Cercospora (leaf spots and pod blights), Phymatotrichopsis omnivora and Macrophomina phaseolina (charcoal rot of maize and soya). The species is also a susceptible host to more than 60 viruses.Trophane alkaloids produced by D. stramonium and related species are poisonous to humans, horses, cattle, sheep, pigs and chickens (Watt and Breyer-Brandwijk, 1962) so it is important to prevent contamination of feed grains by seeds of these weeds. Due to the difficulty and expense of separating the seed from sorghum grain, contaminated samples of the crop may be downgraded or rejected by buyers in Australia (Parsons and Cuthbertson, 1992). Livestock normally avoid eating species of Datura unless other vegetation is unavailable, but may be poisoned by ingesting it as a contaminant of hay, silage or seed screenings (Hightower, 1979).