| Summary: | Saltcedar (Tamarix pentandra Pall.), an exotic plant on much river bottom land throughout the West, is considered by many as a weed that consumes large quantities of water. Plans for eradicating saltcedar thickets to save water for other uses have met with considerable opposition from wildlife and conservation groups which consider saltcedar thickets to be essential wildlife habitat. The use of chemical antitranspirants which would reduce saltcedar transpiration and reallocate water to underflow or channel flow without harming the plant, environment, or human health may provide an alternative to eradication. Eight-hydroxyquinoline sulfate (8-HQS) and derivitives of alkenylsuccinic acids (MDSA and GDSA) are antitranspirants that have reduced saltcedar transpiration in previous tests. Two greenhouse and 2 field experiments with 8-HQS and the mono-methyl ester of n-decenylsuccinic acid (MDSA) indicated that both compounds were equally effective in reducing saltcedar transpiration. The antitranspirant effectiveness of 8-HQS and MDSA was greater in the greenhouse than in the field. In a field test the transpiration of saltcedar plants sprayed with MDSA at 350 ppm was 18 percent less than control for 8 days. The trend of the data from simulated rainfall tests in the greenhouse suggested that rainfall may decrease the effectiveness of both compounds although results were inconclusive. Eight-HQS, because of reported plant and animal cell abnormalities initiated by the compound, may not be suitable for field use. No harmful effects of alkenylsuccinic acids have been identified. Treatment cost estimates were formulated for an aerial application of MDSA on a hypothetical saltcedar thicket. If the evapotranspiration of a saltcedar thicket could be reduced by 35 percent for 2 weeks, on-site reallocated water may cost an estimated 44 dollars per acre-foot. However, if only a 15 percent reduction in evapotranspiration were achieved for 1 week, the estimated cost of reallocated water would increase to 200 dollars per acre-foot.
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