1Contribution from the Agronomy Department, University of Agricultural Sciences, Hebbal-560024, Karnataka.
Two studies were conducted on Parthenium hystirophorus L. during 1976 around Bangalore. The growth of the weed under different soil conditions was studied to deter-mine the factors favouring its better growth. It was observed that Parthenium could grow under varied soil pH. Soil alkalinity depressed weed growth yet the seed production was unaffected, in view of numerous branches. High soil moisture availabi-lity and organic carbon in the soil favoured the plant height, number of branches per plant, total dry matter production and dry matter distribution to flowers. All these eventually lead to higher seed production.
In another study, 22 pre-emergent herbicides were tried to determine their relative efficacy on the prevention of Parthenium emergence. The pre-emergence applied herbicides which completely prevented emergence of Parthenium for 60 days were: terbutryne (5.88 kg/ha), RH8817 (1.96 kg/ha), atrazine (1.23 kg/ha), simazine (1.23 kg/ha), butachlor (3.68 kg/ha) and dimethyl amine salt of 2, 4-D (5.29 kg/ha). Reasonable control of weeds was also obtained with penoxalin (1.37 kg/ha), benthiocarb (1.84 kg/ha), methabenzthiazuron (1.72 kg/ha), bentazon (2.35 kg/ha), sodium salt of 2, 4-D (3.92 kg/ha) and ethyl ester of 2, 4-D (2.65 kg/ha).
