Dursban and diazinon residues in biota following treatment of intertidal plots on Cape Cod - 1967-69.

Details are given of a study carried out in 1967-69 at Cape Cod, Massachusetts, to determine whether the use of Dursban and diazinon for the control of larvae of Culicoides melleus (Coq.) breeding in intertidal sand, C. hollensis (Melander & Brues) and C. furens (Poey) breeding in salt marsh mud and Tabanus nigrovittatus Macq. and T. lineola F. breeding in salt marsh turf would result in harmful effects to non-target organisms, and to determine residue levels in the intertidal fauna and flora [cf. RAE/B 60, 587]. A granular formulation of Dursban applied manually at the optimum concentration of 0.05 lb active ingredient/acre effectively controlled the Culicoides larvae and caused no apparent harm to fiddler crabs (Uca spp.) and other organisms. The residues detected ranged from trace amounts to 2.3 p.p.m. in white oligochaetes (Enchytraeidae), 2.58 p.p.m. in ribbed mussels (Modiolus demissus), 4.62 p.p.m. in fiddler crabs, 14 p.p.m. in Tabanus spp. and 15.7 p.p.m. in marsh snails (Melampus bidentatus). A granular formation of diazinon applied to give 0.2 lb. active ingredient/acre effectively controlled Culicoides but killed small sand organisms. In general, concentrations of diazinon were higher than those of Dursban in the above organisms. Details are also given of the sampling and gas chromatographic procedures used in the analyses, of changes with time in the levels of the residues, and of the duration of persistence of these compounds in substrates of intertidal sand, salt marsh turf, salt marsh mud and sea water.E