The influence of environmental factors on the molluscicidal activity of Euphorbia milii latex.

The present study was undertaken to investigate the influence of biotic (snail size and presence of food during the test) and abiotic factors (temperature, water hardness and concentration of organic materials) on the molluscicidal activity of Euphorbia milii latex. Bioassays were conducted with B. glabrata (10 snails per concentration) and snail lethality was evaluated after 24 hr and 48 hr of exposure to lyophilized latex solutions. Neither the degree of water hardness, nor the presence of food during the test affected latex-induced snail mortality. The snail size had a minor influence on E. milii-induced snail lethality. Newly-hatched (shell diameter < or = 1 mm) as well as young (3-8 mm) snails were slightly less susceptible than older (10-25 mm) mollusks. On the other hand, the molluscicidal effect of E. milii latex was modified by environmental factors such as temperature (i.e., LC50 and LC90 values were halved for every 10 degrees C rise in temperature) and concentration of organic materials in the water (i.e. the higher the concentration of organic matter, the higher the LC50 value). The efficacy of E. milii latex as a molluscicide can be modified by factors such as water temperature and concentration of organic materials, and to a lesser extent by snail size.