Potamogeton natans (broad-leaved pondweed)

Cultural Control

Effective removal by mechanical harvesting (cutting and raking) can be successful in canals (Murphy et al., 1987, 1990). In North America and Western Europe, special barges are used which cut the weeds and also remove them from the water, alternatively cutting machines are mounted on boats or tractors which cut the weeds in streams and small rivers letting the cut plant material float downstream. Mechanical mowing and rolling is widely used in the control of weeds in irrigation ditches (Dunk and Tisdall, 1954; Seaman, 1958).

Chemical Control

Glyphosate and diquat have been used with success in Scotland to control P. natans (Murphy et al., 1990). In English lakes, dichlobenil provided good control of P. natans (Terry et al., 1981). Similar results have been published for French reservoirs (CTGREF, 1978). In Yugoslavia, copper ethylene diamine, terbutryne and paraquat were effective (Arsenovic et al., 1982).

Biological Control

For biological control, grass carp (Ctenopharyngodon idella) has been used successfully in Scottish channels (Murphy et al., 1990), and Polish lakes (Krzywosz et al., 1980). However, a mesocosm-scale feeding study indicated that P. natans and Myriophyllum specatum were avoided if more palatable species were available. In the latter case it was concluded that understocking would lead to dominance of the vegetation by P. natans and M. spicatum (Fowler and Robson, 1978). Of species related to P. natans, P. pectinatus, P. berchtoldii, and P. densus were more palatable to grass carp (German Plant Protection Service, 1975; Fowler, 1978).

The fish Tillapia zillii has been used to control Potamogeton species and other weeds in the western USA (Legner and Pelsue, 1983).