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Monday - December 10, 2007

From: Oceanside, CA
Region: California
Topic: Water Gardens
Title: Effect of herbicides on frogs
Answered by: Barbara Medford and Damon Waitt


I live in a planned development adjacent to a natural waterway that contains native and non native plants. It also is an amphibian habitat with many frogs. The landscape manager has sprayed the area with Monsanto's Rodeo (also sold as Aqua Master)to remove the undesirable plants. To the Rodeo he has added a surfactant, Pro-Spreader. I know that Rodeo is approved for use on waterways, but I am also concerned that the surfactant added is killing the native frogs. Do you have also any information on this? Also, the landscape manager claims that Rodeo is "selective" killing the plants we don't want and not harming others. Is it true that a herbicide would kill some plants and not others? Thank you for you help.


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.


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