Classification of Parasitic Weeds

By: Akash Singh Soares(A-2014-01-005)

IntroductionOut of 2,50,000 plant species, weeds constitute about 250 species, which are prominent in agricultural and non-agricultural system. Under world conditions about 30,000 species are grouped as weeds and are further classified. Among the 10 Classification, one is Based on the Specificity.

On the Basis of Specificity, the weeds are of following types:¡ Poisonous Weeds¡ Parasitic Weeds¡ Aquatic Weeds

Parasitic WeedsThe parasite weeds re either total or partial which means, the weeds that depend

completely on the host plant are termed as total parasites while the weeds that partially depend on host plant for minerals and capable of preparing its food from the green leaves are called as partial parasites. Those parasites which attack roots are termed as root parasites and those which attack the shoot of other plants are called as stem parasites.i. Total Root Parasite- Orobanche cernua on Tobaccoii. Partial Root Parasite- Striga lutea on Sugarcane and Sorghumiii. Total Stem Parasite- Cuscuta chinensis on Lucerne and Onioniv. Partial Stem Parasite- Loranthus longiflorus on Mango

OrobancheIt is a total parasitic weed observed on different host plants according to its different species e.g. Cernua on Tobacco and Sunflower. It is commonly called as Broomrape.

Control Measures£ Proper rotation with pepper, rice linseed, sun-hemp, sorghum, sesame etc. for tobacco area.

£ Glyphosate @0.5 kg a.i./ha is found effective.

£ Orobanche growing outside the crop field should be destroyed by frequent tillage before seed setting.

Images of Orobanche

StrigaAlso called as Witch Weed. It is an annual parasitic herb with a wide range of the host crop plants in India. In India, the common host plants are sorghum, sugarcane, bajara and maize.

Control Measures† Host plants are rotated with cotton, sunflower, cow pea, groundnut, certain beans, and castor to minimize

the infestation of Striga.

† In heavily infested areas, both parasitic weed and crop should be ploughed down at early stage.

† Hand weeding can reduce the weed population.

† Soil may be fumigated with Methyl Bromide.

† Herbicidal Spray of 2,4-D (amine) @1.2 kg a.i./ha on flowers of Striga or pre-planting application of Dicanba or Fenac @2 kg a.i./ha are very effective.

† Use of resistant variety.

Striga in Sugarcane Striga in Sorghum

CuscutaIt is a parasitic leafless herb with golden yellow, shining wiry stem, found on trees, cultivated crops and hedges. Also Called as Dodder or Amarvel or Akashbel.

Control Measures† Cuscuta can be pulled out and buried. It can be controlled by proper crop rotation.

† Paraquat 1% spray with a high volume sprayer will kill dodder.

† The seed of Lucerne are to be treated with 5% to 10% solution of common salt for five minutes. The light seed of the Cuscuta will float on the surface of water.

Cuscuta chinensis

LoranthusIt is a phanerogamic parasite found mostly in the tropics rooting beneath the bark of the trees, particularly Mango. It derives whole of its nutrient from juice of host plants.

Control Measures† Affected branches of the host plants should be periodically cleaned or cut down before monsoon.

† High speed diesel will be helpful to kill the foliage of this parasitic weed.

† Paraquat 1% spray will be helpful to kill the foliage of this parasitic weed.

† Paraquat + 2,4-D @3.5 kg each in 160 litre water/ha with rocker sprayer on the infested area can kill Loranthus by both contact and translocations to be taken to protect the host tree.

Loranthus in Mango