Various methods of removing reeds from a malaria infested region were compared as to their effectiveness in control of Anopheles larvae. It was found that the mechanical or chemical methods of reed destruction usually resulted in the development of horizontal vegetation which furnished shelter for mosquito larvae.
In contrast, a nutria population of suitable density was able to keep the river course and adjacent ponds clear of vegetation for 3 years. The results obtained with feral nutria in the Naaman swamps were confirmed in five fenced pond farms in various regions of the country.
In the area kept permanently clear of weeds by nutria the drainage capacity of the river and ditches was maintained, and the use of insecticide was decreased substantially.