During august 2000,a survey of the sides of railway track from Bangalore City to New Delhi and back enroute parts of Karnataka, Andhra Pradesh, Maharastra, Madhya Pradesh and Uttar Pradesh was made while travelling through train for determining growth and spread of the weed Parthenium hysterophorous L. All along the route, onward and backward, a dense, green continuous mat of parthenium was noticed. No natural barrier or bio-agent was appeared to deter the growth and spread of the weed on either sides of the track. At moisture-laden spots, particularly parthenium plants grew vigorously which well spread canopy up to a meter height. The plants completed life cycle by producing abundant foliage, flowers and seedlings. Zygogramma beetles were not observed on parthenium all along the 3000 km route (one way). No other plant species appeared to compete with the Parthenium weed.

During September 2003, the survey was repeated along the same route by train, onwards and backward. Observations showed that the parthenium plants at several patches were being suppressed and it’s growth checked by other plant species. At several patches, parthenium plants were being displaced biologically by other competitive species. In order to assess the extent of displacement / suppression, a cross section view of the area visible from windows (ca.1m x 1m) of the running train was observed by two observers, one on each side of the track. From the window, approximately 5 to 6m2 area could be scanned . For each states, 200 patches on either sides of the track were scanned. All sightings were grouped into four categories, viz. no displacement of parthenium

Details of 200 scans/state are tabulated below (table 1).

Displacement was a function of the proportion of all sightings under four categories. For instance, displacement would be cent for cent if all sightings were under category 4. The competitive species put up a luxurious growth, produced flowers, pods and developed well spread canopy cover. While parthenium growth at the same spot was stunted, with sparse foliage and no – reproductive parts or few flowers and no seedlings. This was taken as an index of displacement.

The most prominent species suppressing parthenium was undoubtedly cassia sericea l. the other species suppressing parthenium were cassia tora L, echinocha crusaallis(l),bean,xanthinium strumarium rox cassia occidentalis l stylosanthes hamata l and few others which could not be identified . Most of these plants have economic value ,can be used as green manure ,fuel wood and seeds . These plants have no adverse effects on human beings, livestock and crop .The competitive plants vigorous growth indicated effective displacement. A two year study by Chakravarthy et al (1977) (first intl. Conf on parthenium management, vol II, M.Mahadevappa and Patil ,V.C.(eds))173-176,U.A.S,Dharwad),established that parthenium could be effectively checked by competitive displacement principle and plants like c sericea have a efficient and effective mechanism .