The parasitic weeds or heterotrophic plants are conveniently divided into different groups; hemi/partial- or holo/total-parasites, facultative or obligate parasites, root or stem parasites and annual or perennial parasites. Out of about 4000 parasitic plant species, certain species under few plant families; (Orobancheaceae, Convolvulaceae, Loranthaceae and Viscaceae) are considered to be among the most serious agricultural pests of economic importance.