The laboratory tests showed that the diflubenzuron does not present acute toxicity to shellfish and fish, but can affect the survival rate of Artemia salina and Palaemonetes varians, when its concentration rises to the level of its water solubility. The insecticide persistence in sea water had been found to be 3 weeks and its concentration factor in the fish after 52 days of exposure was very low. The use of dimilin in coastal zones for the eradication of caterpillars seems to have an insignificant impact on marine ecosystem, particularly on the molluscs.