Integrated weed management for parthenium

THE OBNOXIOUS weed Parthenium hysterophorus is a thermo insensitive herb. It is a prolific seed producer with seeds having long storage life and can quickly disperse through wind. Vegetative generation occurs from the crown.

The concept of `One year seeding, seven years weeding' is true for Parthenium. It produces about 5000-10000 seeds per plant, which are viable even at immature stage. In dry summer months Parthenium appears in a rosette form. But during rainy season it grows up to 90 cm. height, with profuse flowering and green foliage. It flowers throughout the year.

It causes contact dermatitis in livestock and is reported to be poisonous to sheep. Humans are also affected by this weed with respiratory malfunction and dermatitis. Main toxin responsible for the effect is "Parthenin."

An integrated approach is essential for effective control. Following are the practices that can be adopted to control Parthenium.

A. Cultural method: (i) Hand pulling: This practice is recommended once the weed emerges from the soil. If, area of spread is high a serious hand pulling campaign is needed to control.

(ii) Crop rotation: In infested cultivated land, normal crop is rotated with marigold during rains.

(iii) Allelopathic effect: The weed can be suppressed by Cassia sericea. Its plant leachates have kaolines, which accumulate in the soil and interfere with the weed.

(iv) Composting Parthenium: The weed reaches 50 per cent of seed setting during flowering. The weed left as such in the same area acts as a seed bank because of its higher seed production capacity and extended dormancy period. Hence composting is recommended, as the seeds lose their viability due to the higher temperature during composting.

Cut the Parthenium weed into small pieces by using knife or chaff cutter and spread the material on the ground to a thickness of 10 cm layer. Over this spread Tricoderma viridi and spray urea at 0.5 per cent solution (Generally 5kg urea/ ton of weed material).

This sequence of layers is repeated up to a metre high and finally plastering should be done by with mud/ clay soil. Keep the moisture level at 50-60 per cent. After two weeks, a thorough mixing has to be given.

The compost will be ready for field application after 40-45 days. It is a good source of nutrient and helps to maintain soil properties through aggregate formation. The `Parthenin' content acts as a growth regulator and so the next crop comes up well.

(v) Mulching: Mulching has smothering effect on weeds by restricting the photosynthesis. It also, conserve moisture, lower surface temperature, fertilize the soil, protect from rainy season and improve the soil quality.

B. Biological method: Zygogramma bicolorata, a leaf eating beetle, was identified as a bio control agent which controls Parthenium weed by feeding on the foliage. Recently a rust pathogen Puccinnia abrupta var parthenicola was identified, which is capable of controlling this weed.

C. Chemical method: (i) Non-cropped areas: This weed infestation is generally severe in open waste land, non-cropped areas along railways and roadsides. In such areas spraying of common cooking salt solution at15-20 per cent concentration at active growth stage will effectively control the weed. Application of 2,4-D esters at 2-5 kg a.i/ ha along with wetting agent will also control the weed.

(ii) Cropped areas: Herbicide plays a vital role in cropped area weed management, otherwise crop injury will occur. Pre emergence herbicides such as Simazine, Atrazine for maize, sorghum and sugarcane; Alachlor and Butachlor for pulses and cotton respectively are the selective herbicides for Parthenium control.

M. Ramamoorthy, B. Uthayakuar, J. Sundersingh Rajapandian & A. Muthusankaranarayanan

AC & RI, Killikulam-628252, T.N.

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