| Summary: | Phreatophytes in the western United States consume water at a rapid rate through transpiration and present a serious water wastage problem. Initial attempts to control wastage were through eradication by mechanical means. These methods met with little success due to high costs, regrowth abilities of phreatophytes and opposition from wildlife interests that consider phreatophyte vegetation essential wildlife habitat. Chemical antitranspirants, which would reduce phreatophyte transpiration without harming the plant, provide an alternative to eradication. However, the impact of these chemicals on the environment had not been investigated. Aerial application of an antitranspirant would introduce a pollutant into the aquatic environment, so effects of these chemicals on fish were investigated. Acute toxicity tests using mosquitofish, Gambusia affinis, were performed at 20°C and 25°C using film-forming antitranspirants, Folicote and Mobileaf. Both antitranspirants were found practically non-toxic. However, during toxicity experiments, both antitranspirants demonstrated oxygen consumptive tendencies. Further tests without fish showed significant dissolved oxygen demand by Folicote. A field experiment was conducted during actual application of Mobileaf on saltcedar (Tamarix sp.) to indicate any drastic changes or effects antitranspirants may have on local insect populations. Due to an apparent impoverished insect fauna and other limiting factors, no conclusive results were obtained.
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