Preventative measures: A Risk assessment of
Myriophyllum aquaticum for Australia was prepared by Pacific Island Ecosystems at Risk (PIER) using the Australian risk assessment system (Pheloung, 1995). The result is a score of 20 and a recommendation of: reject the plant for import (Australia) or species likely to be a pest (Pacific).
Physical: As plants reproduce vegetativly mechanical methods which will cut up rhizomes and stems will only increase spread.
Chemical: Washington State's Department of Ecology (2003) states that, "Although M. aquaticum is considered by some to be susceptible to herbicides, it is difficult to achieve complete control. The emergent stems and leaves have a thick waxy cuticle and it requires a wetting agent to penetrate this cuticle. Often the weight of the spray will cause the emergent vegetation to collapse into the water where the herbicide is washed off before it can be translocated throughout the plant.
Biological: Biological control is used effectivly in South Africa, one insect species of the genus Lysathia is being used (Mabulu, L.Y., pers. comm., 2004). Parrot feather has a high tannin content so most grazers, including grass carp, find it unpalatable (Washington State's Department of Ecology, 2003). 
