Dear sri Nprabhs,
Please follow the information on Parthenium
Scientific name: Parthernium hysterophorus
Common name: Carrot grass, congress grass
Family: Asteraceae
Biology and habitat: It is a noxious exotic weed which has spread to many parts for country covering 5 million ha. It is annual plant (thermo and photoinsensitive). reaching 2m tall in good soils, usually 50 to 150cm, germinating after rain at any season, flowering in 6 to 8 weeks, and senescing with drought or frost. the stem is branched and covered with trichomes.
Leaves are pale green, lobed, hairy, initially forming a basal rosette of strongly dissected leave that are up to 30 cm in length. Young roselles with their radial leaves closely press to the ground, allow no other species to come up in their vicinity. The number of leaves per plant ranges from 6 to 55. Flower heads are creamy white, about 4 mm across, arising from the leaf forks
Reproduces by small seeds lasting up to 20 years in soil, induced dormancy on burial The plant is capable of flowering when one month old and remains in flower for 6 to 8 months It produces 5000-10000 sedds/plant. The toxin parthenin is responsible for allergic dermatitis and mental depressions in human beings. Plant prefer moist shady and organic rich habitat. tTey have remarkable adaptation to environment extremes which exerts allelopathic influence on the neighboring plant species, the seed leachates inhibit germination of other weed seeds cause allergies and skin diseases. Seeds are light in weight and armed with pappus and disseminated by wind, water birds and animals. It is not only an agricultural weed but also a municipal weed.
Control:
Management
1. Mechanical and cultural: Manual uprooting of Parthenium before flowering and seed setting is the most effective method. A plant in flower will aid in the dispersal of pollen grains, resulting in allergic reactions.
2. Ploughing the weed in before the plants reach the flowering stage and establishing pastures or other plants may be effective
3. Competitive replacement of Parthenium can be achieved by planting species like Cassia sericea, C. sparsiflorus, Amaranthus spinosus, Sida acuta, Tephrosia purpurea, Stylosanthes scabra and Cassia auriculata, which will compete with the weed and reduce its population.
4. Similarly, planting Cassia tora will help to cover and suppress the growth of Parthenium. In certain parts of India, crop rotation using marigold (Tagetes spp.) during rainy season, instead of the usual crop, is found effective in reducing Parthenium infestation in cultivated areas.
5. 2,4-D, paraquat provide effective control of weed.
6. Pre-em application of atrazine, alachlor, butachlor prevent seedling emergence up to 2-5 months.
7. Chlorimuron @0.2-0.4kg/ha and metasulfuron @0.003-0.0045 kg/ha as pre-em.
8. Already established vegetation: in non cropped areas 2,4-D esters @2-5kg/ha or common salt @ 15-20% at actively growing stage.
9. Biological. The leaf-feeding beetle Zygogramma bicolorata and the stem-galling moth Epiblema strenuana are widely used in several countries to manage Parthenium. Z. bicolorata is now widely used in India to control Parthenium. The moth significantly reduces flower and seed production of the weed, especially at a young age.
G.Anandarao B.Sc(Ag)
