A study was conducted with a wettable powder formulation of 1-methylcyclopropene (1-MCP) to determine the effects of surfactants, spray volume, nozzle type, and rain fastness on the efficacy of 1-MCP to protect tomato plants from the epinastic effects of ethephon. 1-MCP at 25 and 50 g·ha−1 protected tomato plants from 250 and 500 g·ha−1 of ethephon. Of the three best surfactants tested, two (Dyne-Amic and Silwet L-77) contained silicone and one (Herbimax) an emulsified petroleum oil. The efficacy of 1-MCP increased with an increase in spray volume from 150 L·ha−1 to 400 L·ha−1, suggesting that an increase in leaf coverage leads to greater protection and that the translocation of 1-MCP is limited within tomato plants. There was no significant effect of spray nozzle type on 1-MCP activity. 1-MCP appeared to be rainfast within 15 min after application.