Ask Mr. Smarty Plants

To answer your last question first: Yes, there is such a thing as a "selective" herbicide, but Rodeo is not selective. It kills all plants including brush, grasses, herbaceous broad leaves, etc. It is only selective to the extent you spray it on the plants you want to get rid of and not the ones you want to keep. From this Aqua Master website, you can learn more about Rodeo's use to control aquatic plants.

Now let's get to those frogs and surfactants. The scarcity and sometimes total disappearance of many species of amphibians has been concerning specialists in that field for many years. Frogs "breathe" largely through their skins. Because the oxygen is dissolved in an aqueous film on the skin and passes from there to the blood, the skin must remain moist at all times; this makes frogs susceptible to many toxins in the environment.

Nonionic surfactants are added to herbicides so that the herbicide will adhere to the leaf surface and penetrate into the leaf's tissue. Given the sensitive nature of amphibian skin and the function of surfactants, it is not surprising that they could be a problem for amphibians. In fact, there is a growing body of scientific evidence linking nonionic surfactants with endocrine disruption in amphibians. Time prevents Mr. SP from going into great detail about endocrine disruptors in amphibians. Suffice it to say...it is not a good thing. If you google "nonionic surfactants amphibians", you will see what I mean.