Abstract:
Invasive alien plants have caused extensive economic and ecological
damages throughout the world. Many coconut cultivated lands which
dominated with grasses in Southern Sri Lanka have been invaded by
recently introduced ornamental ground cover plant, Wedelia trilobata, and
now it has become a big problem for the cattle feeding. Enough attention
has not been focused yet to understand its vigorous growth and competition
and hence the relevant information is not available in existing literature. A
study on this weed is therefore very much important. No seed germination
of W. trilobata was observed under laboratory conditions and therefore the
rapid invasiveness was investigated throughout the vegetative propagation.
Competitive ability of W. trilobata with the grass Axonopus compressus
was studied under the green house conditions keeping the total plant density
constant while changing the densities of the two components. Covering
effect and allelopathic effect of W. trilobata on the grass and growth rate of
each species was also studied. Fresh weight, dry weight, length of the stem
and root, root/shoot ratio were taken as the measurements. With the
increase of W. trilobata density, shoot length and root length of A.
compressus were gradually decreased. Covering rate of W. trilobata varies
in different locations. It spreads 62.86cm2 month7m2 in Deniyaya area
compared to 51.71cm2 month/ m2 in Devinuwara. Considering
alleolapathic effect, 50gL' of W. trilobata leaf extraction significantly
affected the growth of A. compressus. These physiological parameters are
advantageous to implement successful and efficient management programs
for Wedelia trilobata.
