RESPONSE OF ELODEA-CANADENSIS MICHX AND MYRIOPHYLLUM-SPICATUM L TO SHADE, CUTTING AND COMPETITION IN EXPERIMENTAL CULTURE

Elodea canadensis Michx. and Myriophyllum spicatum L. are widespread n uisance aquatic plant species. Their ecology is regarded as similar. B oth species have been previously classified in terms of established-ph ase survival strategy as 'competitive disturbance-tolerant' species. E xperimental data are presented to show that although this broad catego risation of strategy is probably correct for the two species, it is po ssible to demonstrate significant differences in terms of response to disturbance and competition. Less difference was discernible in their comparative response to stress. The drawbacks of applying broad descri ptive terminology when dealing with two species of similar strategy ar e addressed. The results help explain reports of variable success in a ttempting to manage these two species using disturbance-based weed con trol measures, and suggest that Elodea is even less susceptible to suc h measures than Myriophyllum.