Abstract
The reduction of herbicide applications is a main research priority in recent years. In order to study the effect of individual post-emergence application of sugar beet broad-leaf herbicides at four to six true-leaf stage of weeds, experiments were conducted during 2013. Treatments included untreated control and several rates of desmedipham + phenmedipham + ethofumesate, chloridazon and clopyralid on Portulaca oleracea, Solanum nigrum, Amaranthus retroflexus and Chenopodium album. A completely randomized layout with three replications was used for each herbicide. Three weeks after spraying (WAS), plants were harvested and measured their dry weight. These herbicides were more effective to control Portulaca oleracea than other weeds, thereupon minimum dose required for a satisfactory efficacy of 90% reduction of Portulaca oleracea aboveground dry matter (ED90) were 299.22, 1138.31 and 129.44 g a.i ha-1 of desmedipham + phenmedipham + ethofumesate, chloridazon and clopyralid, respectively. Solanum nigrum was more affected by clopyralid application (132.40 g a.i ha-1), and did not make significant difference in Portulaca oleracea. Chloridazon had lower effect for control of Chenopodium album due to existence of powdery covering on abaxial side of the leaves. Biomass ED50 or ED90, based on log-logistic dose–response curves, for Chenopodium album was considerably higher than other species. These results showed that tank mixtures with other herbicides may be required for satisfactory weed control and reduction in applied herbicides doses.
Highlights
Sugar beet is a low growing crop and many weeds grow taller than sugar beet (Odero et al, 2008)
Portulaca oleracea and Solanum nigrum showed the highest susceptibility to desmedipham + phenmedipham + ethofumesate, so that application of 308.25 g a.i. ha-1 of herbicide resulted in 100 percent control 21 days after treatment (Tab. 1)
Desmedipham + phenmedipham + ethofumesate were more potent than that of chloridazon and clopyralid against Portulaca oleracea, Solanum nigrum, Amaranthus retroflexus and Chenopodium album based on our experiments
Summary
Sugar beet is a low growing crop and many weeds grow taller than sugar beet (Odero et al, 2008). There are few herbicides available to control broadleaf weeds in sugar beet in Iran. Clopyralid is a selective post-emergence herbicide that is a member of the pyridinecarboxyli acid family that has activity on a number of annual and perennial broadleaf weeds (Norsworthy and Smith, 2005) in sugar beet in Iran. Desmedipham + phenmedipham + ethofumesate, phenylcarbamates + benzofuranyl alkanesulfonate herbicides are widely used for post-emergence broad-leaved weed control in sugar beet (Deveikyte and Seibutis, 2006; Markovska et al, 2012). Desmedipham, phenmedipham and chloridazon, are photosystem II (PSII) inhibitors, mostly absorbed by roots, and by foliage (Cioni and Maines, 2011). Ethofumesate is fatty acid and lipid biosynthesis inhibitor which readily absorbed by emerging shoots and roots, and translocated readily to the foliage. Post-emergence applied ethofumesate is poorly absorbed by maturing leaves with a well developed cuticle (Jonson et al, 1989)
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