Efficacy of some methods controlling leeches in water

Experiments were carried out on the influence of quicklime, ammonia water, ‘Neguvon’ — Bayer and desiccation on the vitality of leeches. It was found that the efficacy of quicklime depends on its CaO content, on the dose of this compound, and, above all, on the pH of calcium hydroxide formed by mixing quicklime with water. The borderline value in this case is pH = 8.6. Quicklime containing 49% CaO did not affect the mature forms of leeches or their larvae in cocoons. The efficacy of other kinds of quicklime (53% CaO, 93% CaO and 99% CaO) also depended on the pH produced. Quicklime containing 99% CaO proved the most effective in destroying mature leeches and their cocoons; at the concentration of 250 ppm, it produces a pH higher than 8.6 (Table I).In acceptable doses, ammonia water affects neither mature leeches nor their larvae in cocoons.‘Neguvon’ — Bayer, though effective against mature leeches, does not affect the vitality of the larvae in cocoons in doses acceptable for practical use.Under laboratory conditions, drying up kills leech larvae in 24 h. This is therefore a radical means of combatting these parasites.