hermit,

Texas A&M does lots of good research on ponds and fisheries. Here is a link to a study they re-published that indicated that it was almost certainly the surfactant (in basic Roundup) that was toxic to the amphibians:

http://fisheries.tamu.edu/files/201...-in-Aquatic-and-Upland-Natural-Areas.pdf

From the article:

"Most glyphosate-containing products that are registered for aquatic use are manufactured without surfactant (Touchdown Pro, the exception, contains a different surfactant) so that the applicator can use one of the many commercial surfactant products available that have low toxicity to aquatic organisms and instructions for aquatic applications. While the contents of commercial surfactants is proprietary information, they are regulated and only contain ingredients that are approved by EPA or the Food and Drug Adminstration."

There are other glyphosate products (besides Touchdown Pro) developed since that study was published that are designed for spraying aquatic plants. I would assume they would be safe to spray on your terrestrial shoreline vegetation. (I would rather have a "safe" surfactant, rather than no surfactant - so that you kill your waxy-coated weeds with less herbicide.)

One example is Glyphosate 5.4 (by Alligare). It does contain a surfactant, but I assume it is safe because it is approved for aquatic use. (I have used and liked some of their other herbicide products.)


One other reason glyphosate is such a widely used systemic herbicide is that it really tries to bond with soil particles once it hits the ground. Usually, if you don't have any spray drift, then it only kills the plant you treated and none of the surrounding plants are harmed.

For that reason, I would spray part of your shore plants each time the wind was favorable for that section. For example, when you have a gentle, but steady, wind from the north, then I would step into the lake with my muck boots and spray the weeds on the south shore - so all of my drift lands on soil and none in the water.

Good luck on your project! We like happy frogs and tadpoles!