Persistence of Dicophen, B.P., Deposits from Suspensions and Emulsions on Bark in the Northern Guinea Savannah Zone of Nigeria: Investigations by Chemical Means and Bio-Assay

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Riordan K.
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1.Formulations of suspensions and emulsions containing 2 % and 5 % dicophen were sprayed on to bark in the Northern Guinea Savannah zone of Nigeria during the dry season (January). 2. The deposits produced were studied by bio-assay against female G. palpalis until the middle of the subsequent wet season (July) and by chemical analysis until the beginning of the subsequent dry season (October). 3. Large amounts of dicophen were shown by the chemical analyses to remain in "and/or on the sprayed bark for all the formulations up to 40 weeks after spraying, when testing stopped. 4. Up to 10 weeks, and probably up to at least 26 weeks, after spraying all the deposits remained very toxic to the test flies. 5. Deposits produced by spraying formulations at 5% active content were more toxic at all ages tested than were those from 2% formulations. 6. Deposits from suspensions were probably weathered faster than those from emulsions, mainly by rain, but remained more toxic, possibly because less of the dicophen content sorbed into the bark.
Journal Of Entomology, p. 133-137