Allelopathic effect, Biological control, Parthenium hysterophorus, Survey, Zygogramma bicolorata

Systematic surveys of Parthenium hysterophorus L. infested regions on 12  selected national highways of North-Eastern India were conducted during 2009-2011.  In all the surveyed sites, Parthenium hysterophorus was present but its abundance was more during the month of June to August. Complete inhibition of Parthenium seed germination was recorded at 20% of leaf and stem extracts of Cassia sericea, Mimosa pudica and Cassia tora.  Different stages of Zygograma bicolorata (grubs to adult) showed reduction in plant height, shoot length, root length and biomass of Parthenium when exposed in mosquito net cages.