Estimation of thresholds for weed control in Australian cereals

Abstract

Summary A non‐linear model relating crop yield to the density of weeds was fitted to nine Victorian weeds to evaluate their competitive abilities. The weeds were: Acroptilon repens (L.) DC. (creeping knapweed), Chondrilla juncea L. (Skeleton weed, Raphanus raphanistrum L. (Wild radish), lolium rigidum Gaud. (Annual ryegrass), Lithospermum arvense L. (White iron weed), Brassica tournefortii Gouan (Wild turnip), Lamium amplexicaule L. (Deadnettle), Fumaria parviflora Lam. (White fumitory) and Amsinckia hispida (Ruiz & Pav.) I.M. Johnston (Amsinckia). Where more than one experiment was available for a weed, the net return for a herbicide treatment over a range of weed densities was calculated to obtain the economic threshold density. Generally, the economic threshold densities within a weed species were the same order of magnitude, except for the perennial Chondrilla Juncea L., For this species data were collected in years of contrasting rainfall. The model used here is discussed in view of the threshold approach currently used in continental Europe.

Interferência de capim-arroz (Echinochloa spp.) na cultura do arroz irrigado (Oryza sativa) em função da época de irrigação

“…Resultados de perdas superiores a 100% são biolog icamente irreais e ocorrem quando a amplitude de população de plantas daninhas é excessivamente estreita ou quando os maiores valores da população não são suficientes para produzir resposta assintótica de perda de produtividade (Cousens, 1985;Yenish et al, 1997;Askew & Wilcut, 2001;Agostinetto et al, 2004). Optou-se por não limitar as perdas de produtividade em 100%, para não influenciar a estimativa do parâmetro i, o que poderia resultar em menor previsibilidade (Streibig et al, 1989). Resultados semelhantes aos encontrados neste trabalho foram observados por Swinton et al (1994), Askew & Wilcut (2002) e Agostinetto et al (2004).…”

Adaptive Differentiation of Quantitative Traits in the Globally Distributed Weed, Wild Radish (Raphanus raphanistrum)

“…Thought to be native to the Mediterranean basin (Hulten and Fries 1986;Holm et al 1997), wild radish has successfully colonized a variety of locations, leading to its naturalization on all continents except Antarctica (Holm et al 1997). Not only has wild radish colonized these new areas, but also it has become a major agricultural weed, causing yield losses in a variety of crops in North America (Webster and MacDonald 2001;Warwick and Francis 2005), Europe (Bostrom et al 2003), and Australia (Streibig et al 1989;Cousens et al 2001). Due to the self-incompatibility system of wild radish (Sampson 1964) and its lack of vegetative reproduction, this species relies completely on pollination by insects for reproduction.…”

The biology of Canadian weeds. 132. Raphanus raphanistrum L.

“…In Australia, R. raphanistrum is considered one of the most competitive weeds of wheat in terms of yield loss (Streibig et al 1989;Cousens et al 2001). In an Australian weed survey in winter crops, R. raphanistrum was one of the three most widespread and abundant weeds, and the one whose spread was the most difficult to control, particularly in the southern and western regions where herbicide resistance has developed (See Section 11) (Alemseged et al 2001).…”