The effect of seven l-amidino-o-alkylisourea sulphate compounds on the germination of five plant species including carrot grass (Parthenium hystarophorous L.) was investigated. A 10-3M concentration, n-butyl derivative completely inhibited germination of Parthenium without affecting wheat (Triticum aesthum ‘Kalyan Sona’), corn Zea mays L., ‘Composite maize, A-51-54’), gram Cicer arietinum L., Nrisingpur bold’). The spectrum of activity of iso-butyl derivative was complementary to that of n-butyl’ derivative. Methyl derivative inhibited germination of Parthenium by as much as 90% at 10-2 M concentration without'affecting the other species. In certain respects, n-butyl derivative was found to be superior to 2,4-D on which could control Parthenium.
