HERBICIDE TRIALS IN THE SNAIL HABITATS OF THE EGYPT 49 PROJECT.

The molluscan hosts of Schistosoma haematobium, Schistosoma mansoni and Fasciola spp. have been found to flourish in association with certain submersed, floating and emergent weeds in the irrigation system of the Egypt 49 project area. The efficacy of acrolein in killing Potamogeton crispus, an important submersed weed, has been previously established. The present paper deals with field trials of different herbicides, alone or combined, against the other predominant types of floating and emergent weeds-Eichhornia crassipes, Panicum repens, Typha ungustata and Scirpus inclinatus. The trials showed that some of the herbicides are effective and have economic advantages over the manual removal of weeds, besides eliminating the health hazard involved in manual removal. Laboratory tests showed that the herbicides also have ovicidal properties. Aquatic-weed control by the use of appropriate herbicides as an adjunct to molluscicides is therefore advocated.