1 Contribution from the Agronomy Department, University of Agricultural Sciences, Hebbal, Bangalore-560024, Karnataka.
Two separate studies involving selected pre-emergent herbicides, post-emergent herbicides and mechanical control of Parthenium at blooming stage under wasteland condition were made during late kharif 1977 to compare the effectiveness and economics of different control methods. Among the post-emergent herbicides, diquat (1,1’-ethylene-2,2’-dipyridylium bromide) at 0.5 kg/ha caused cent per cent mortality by 15th day, while other herbicides like MSMA (Mono sodium methane arsonate) at 2.61 kg/ha, glyphosate [N-(phosphono methyl) glycine] at 0.9 kg/ha, 2,4-D sodium salt (sodium salt of 2,4-dichloro phenoxy acetic acid) at 6.0 kg/ha, 2, 4-D amine salt (5.4 kg/ha), dicamba (2-methoxy-3, 6-dichlorobenzoic acid) at 2.05 kg/ha and picloram (4-amino-3, 5, 6-trichloropiColinic acid) at 1.61 kg/ha, caused 98 to 100% mortality by 45th day after spraying. 2, 4-D compounds were slightly slower in causing mortality of the weed. All herbicides reduced dry weight of the weed considerably. The fresh weed emergence count made upto 90 days after complete mortality of the weed indicated that picloram had the least weed count (1/sq. m), followed by dicamba (7) and 2, 4-D compounds (22–24). While it was high in MSMA, glyphosate and diquat (254 to 362/sq. m.) sprayed plots. The weed count in the control plot was 676/sq. m. Cutting the weed to the ground level caused only 20% mortality. Uprooting of the weed did not result in regrowth of the weed and there were innumerable fresh sprouts. Among the pre emergent herbicides, atrazine (2-chloro-4-ethyl amino-6-isopropylamine s-triazine) at 1.25 to 1.4 kg/ha, terbutryne (2-methylthio-4-ethyl amino-6-ter-butyl amino s-triazine) at 6.0 kg/ha and RH 8817 (coded product, 2.8 to 5.8 lit/ha of commercial formulation) were most effective in preventing the weed emergence upto 150 days after spraying followed by 2,4-D amine salt (2.8 to 5.0 kg/ha) and 2, 4-D Na salt (2.8 to 4.0 kg/ha). 2, 4-D slow release (1.4 to 2.8 kg/ha) was not so effective as compared to other 2, 4-D compounds. However, this needs confirmation. The study indicated utility of pre and post-emergent herbicides application in succession for better control of the weed under wasteland condition to a reasonable period of time. The herbicides proved economical than mechanical methods.
