Abstract
The effect of the weed Abutilon theophrasti M. (common name: velvetleaf) on the growth of cotton grown in the Guadalquivir Valley, was studied by examining the influence of weed density on growth of the weed and that of cotton. Velvetleaf impeded normal cotton growth caused production losses as a result of the stress the cotton was subjected to. Additionally there was competition among velvet leaf plants at high velvet leaf densities. The influence of velvetleaf density in coexistence with cotton has been also studied evaluating weed effect on the biomass of cotton and its production. Additional determinations included the velvetleaf seed production capacity per unit area and seed production per plant. These determinations were adjusted to hyperbolic, inverse linear and logistic models. Last, the economic damage threshold (EDT) was calculated using the efficiency level in control of velvetleaf in cotton. In this calculation the treatment cost and losses caused by the weed, in the crop, were taken into account. The EDT varied between 0.1 and 0.5 velvetleaf plant m-2, depending on the control methods used.
Highlights
Abutilon theophrasti Medik is an annual weed which, like cotton (Gossypium hirsutum L.), is a member of the family Malvaceae.For a long time this weed has infested crops of cotton, maize, potato and irrigated sunflower
Cotton, which accounts for the largest area of crop production in Andalusia, due to its high economic value (Rodríguez-Ocaña and Ruiz-Avilés, 1996), is currently the crop most severely affected by velvetleaf in Andalusia
Velvetleaf has infested ca. 32% of the total cotton area cultivated in Andalusia (Cortés-Martín et al, 1998)
Summary
Abutilon theophrasti Medik (common name: velvetleaf) is an annual weed which, like cotton (Gossypium hirsutum L.), is a member of the family Malvaceae. Velvetleaf densities of 20-30 plant m–2 resulted in the highest number of viable seeds for reseeding (Zanin and Sattin, 1988) and the weed increased biomass plasticity relative to maize crop (Lindquist and Mortensen, 1997). Smith et al (1990) found an inverse linear relationship between the amount of DM produced by the weed and cotton lint obtained They found that the weed could compete with the crop for up to 95 days after emergence (i.e., until the onset of senescence). According to these authors, the decrease in lint production was correlated with linear increases in velvetleaf height. Because velvetleaf is thought to be difficult to eradicate once it has a well-developed soil seed bank (Saavedra et al, 1995), the present work was undertaken to: 1) examine competition of the weed with cotton, 2) establish an economic damage threshold for treating cotton crop infested with the weed
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