Natural occurrence of pathogens, insect and competitive plants to Parthenium hysterophorus

During the survey diseases such as Sclerotinia stem rot, Alternaria leaf spot, phyllody and leaf curl (virus) were recorded from low to moderate extent with very low potential of Parthenium suppression. Mexican beetle (Zygogramma bicolorata) was recorded in all surveyed districts during the years in moderate to low level. Monthly temporal variations were also observed with respect to the infestation of Mexican beetle with maximum activity during August-September and minimum during January-February. The population of P. hysterophorus was recorded from all the sites and it was found as one of the most prevalent weed species in less disturbed roadsides as well as highly disturbed crop lands and residential areas. Highly disturbed habitats (crop lands & residential areas) showed greater infestation of Parthenium (mean relative frequency= 29.3%, relative density= 33.4% & importance value= 62.85) as compared to less disturbed roadside habitat (mean relative frequency= 4.8%, relative density= 3.8% & importance value= 8.66). The most important competitive weed flora to Parthenium, Sida acuta, Peristrophe paniculata, Setaria verticillata, Achyranthes aspera, Cassia tora and C. occidentalis. Two plant species i.e. P. paniculata and S. verticillata were recorded as strong new competitors to P. hysterophorus.