A measure which can be successful in controlling leeches is bait trapping. After feeding, the leeches will have difficulty leaving the can. Destruction of the contents of the can will help in reducing the size of the leech population. Ducks have also been used to control leech populations, but an over abundance of ducks can create other more serious problems. In order to keep ducks near your area for leech control they will also have to be fed.
Duck feed is high in phosphorus and travels rapidly through the duck's digestion system.
A readily available form of phosphorus is then added to the lakes. If the lake is small and the ducks numerous, enough phosphorus can be added to the lake to cause algae to grow. Ducks are also an intermediate host for a number of parasites that may not be desirable in a swimming area. Water level manipulation can be used to control bloodsuckers on small private ponds. Dropping the level of the pond at least four feet after ice has started to form on the pond will freeze the leeches in the mud.