parasitic weeds depend on the host plants for their nutrition. They penetrate the vessel of the host plant with the special organs the haustoria and absorb water and nutrients. This way they affect the growth of the host plant.
Parasitic weeds are either total or partial parasites.
Total parasites: they are completely dependent on the host plant for nutrients. These are of two types. 1)Total root parasites – for example, Orobanche sp. or Broom rape. Host plants are Mustard, Tobacco, Chilli, Brinjal, Potato. Managed by the spray of Glyphosate. 2)Total stem parasites- for example, Cuscuta or Dodder. Host crops are Lucern and Onion. Managed by the spray of Paraquat.
Partial parasites: depend on host plants for minerals and are capable of preparing their own food. These are of two types 1) Partial root parasites- for example, Striga sp. or witch weed. Host plants are sorghum, maize, sugarcane, sunflower. Managed by the herbicidal spray of 2,4-D on or pre-plant application of Decanba. 2)Partial stem parasites- for example, Loranthus sp. Host plants are plantation crops like mango, sapota, etc. Managed by the spray of paraquat or paraquat + 2,4-D.