INSECTICIDES FOR PREVENTING BARNACLE SETTLEMENT

Abstract

During the summer of 1950 experiments were made to test the use of insecticides for preventing the fouling of oyster spat collectors by the barnacle Elminius modestus.The insecticides used were DDT, BHC (benzene hexachloride‐γ‐isomer) and dieldrin (hexachloro‐epoxy‐octahydro‐dimethano‐naphthalene), made up as 5% solutions and tested on egg‐box collectors and quarry tiles. The tiles were used for frequent observations on settlement.When the solutions were sprayed on to the surfaces, in sufficient quantity to give a covering of 200 mg./ft.2 of active insecticide, none of them interfered with either barnacle or oyster settlement.When the test surfaces were dipped in the solutions, DDT and BHC prevented barnacle settlement almost completely, while dieldrin reduced it by approximately 50%. Settlement of Ostrea edulis was also reduced on the treated surfaces.Urea‐formaldehyde resins made up as varnishes, to which DDT or BHC had been added, were also tested. A varnish incorporating 20% by weight of DDT provided an effective anti‐fouling compound which lasted at least 3 months and completely prevented barnacle settlement.The possibility of insecticides dissolving into the water and inhibiting barnacle growth on adjacent surfaces is discussed.