Document Type: Research Paper
Department of Agronomy, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran.
Registered dose of herbicides may be higher than rate required for controlling
weed species depending on growth stages. In order to study the effect of individual
post-emergence application of 2,4-D plus MCPA and three sulfonylurea herbicides at
four- to six-true leaf stage of weeds, experiments were conducted in 2011 at the
greenhouse of Agricultural Faculty of Ferdowsi University of Mashhad, Iran.
Treatments included untreated control and several rates of 2,4-D plus MCPA,
foramsulfuron, nicosulfuron and nicosulfuron + rimsulfuron on redroot pigweed,
common lambsquarters, common purslane and black nightshade. These herbicides
were more effective to control redroot pigweed than other weeds (except
nicosulfuron + rimsulfuron), thereupon minimum dose required for a satisfactory
efficacy of 90% reduction of redroot pigweed aboveground dry matter (ED90)
were 375.26, 23.51 and 63.81 g a.i h-1 of 2,4-D plus MCPA, foramsulfuron and
nicosulfuron, respectively. Nicosulfuron and nicosulfuron + rimsulfuron did not
control common lambsquarters effectively. Foramsulfuron had the lowest effect on
black nightshade and common purslane, so that minimum dose required for a 90%
reduction of black nightshade and common purslane aboveground dry matter were
52.42 and 60.26 g a.i h-1, respectively. Thus, these results showed that tank mixtures
with other herbicides effective in controlling broadleaf weeds may be required for
satisfactory weed control and reduction in sulfonylurea herbicides doses.
Keywords: Broadleaf weeds; Dose-response curve; Effective dose; Growth stage;