Environmental Impact of the Fungicide Triphenyltin Hydroxide after Application to Rice Fields

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Abstract
Methods were developed to analyze triphenyltin hydroxide (TPTH) in rice field water and soil. Treatment of a rice field paddy with 1.12 kg of TPTH per ha resulted in an average water concentration of 146 ppb at 2 h post treatment, and this steadily declined to below detectable limits (0.8 ppb) by day 24; the average soil concentration was 56 ppb at 2 h, and this increased to 340 ppb at 3 days and then steadily declined to 17 ppb by day 24. All aquatic fauna as well as floating algae were killed on the treated plot. Restocking of mosquito fish, Gambusia affinis (Baird and Girard), in cages on the plot showed residual toxicity (40% or more mortality) for 15 days after treatment. The populations of mosquito larvae, chironomids, and ostracods began recovering after 5 days, but there was no recovery of cladocerans or copepods by 24 days. It is apparent that a single application of TPTH drastically affects mosquito predators, and residual toxicity delays the reestablishment of these organisms, thus enhancing resurgence of the pest population. The side effects of TPTH are so great that its use on rice would virtually eliminate any possibility of the integrated control of mosquitoes.

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