General Recommendations Regarding Invasive Species Control and Potential Impacts on Rare Herps
In general, very little information is available on impacts of invasive species control and herps, particularly Phragmites control and the species of interest in the table. There have been a small number of studies that have looked at impacts of different glyphosate herbicides and surfactants on amphibians (several frog species and a couple of salamanders), particularly embryos and larvae. There is much less published information available on impacts of herbicides and reptiles with only a couple of studies that have looked at impacts on turtle eggs and perhaps one or two that have looked at impacts on a couple of species of snakes. Thus, the phenology table and species vulnerability to Phragmites control measures are based on general results or inferences from currently available information. Since we don’t have a lot of research information on the impacts of Phragmites control measures, esp. herbicide use, on these species, and given the species’ vulnerable status, we should carefully consider the treatments and potential for adverse impacts and try to take a conservative approach to control measures if possible. More research on impacts of Phragmites control measures on the specific herp species of interest and different life stages is needed.
1)The “Habitat Management Guidelines for Amphibians and Reptiles of the Midwest” (HMG) developed by the MW Partners in Amphibian and Reptile Conservation (MW PARC) recommends avoiding the application of herbicides near water sources, both ground and surface waters or wetlands, if at all possible.
2)The HMG also recommends following the directions for applying the herbicide and using spot treatments rather than broadcast applications to avoid over application and airborne drift.
3)Several studies have found that it is primarily the surfactants (e.g., POEA) that can cause mortality of tadpoles and juvenile frogs, more so in some cases than the glyphosate herbicide itself. Rodeo and surfactant NPE have been found to be moderately toxic to tadpoles (Trumbo 2005). Glyphosate with surfactant POEA also has been found to be moderately toxic to tadpoles. Based on this, use of surfactant-free glyphosate herbicides – e.g., Accord, Rodeo are recommended. Some studies also have found that larval amphibians (Gosner stage 25) are more sensitive to chemical contaminants than newly hatched embryos or juveniles/adult amphibians (Edginton et al. 2004). Herbicide use during the larval stage should be avoided or minimized as much as possible to minimize potential for adverse impacts to amphibian populations.
4)Based on a couple of studies, neonates or young reptiles may be more vulnerable to herbicides/chemical contaminants than adults. However, adult reptiles have been found to bioaccumulate chemical contaminants which can lead to adverse impacts.
5)Controlling Phragmites in wetlands may have less impact on herp species when individuals are spending more time in the uplands outside the wetlands (e.g, turtles during the nesting season, snakes during the egg-laying or birthing season, during hibernation for some species) or when individuals are buried in the substrate, under cover, or less active in general (e.g., during hibernation, during hot, dry weather).
a. Based on this, ideally, treatments (herbicide application, fire, etc.) should be conducted in early spring prior to emergence, during mid- to late summer when weather is usually very hot and herps are aestivating or less active, or in late fall when herps in the wetlands have entered or about to enter hibernacula, if possible, to minimize the potential for adverse impacts to herp species.
6)Survey for rare species should be conducted prior to, during, and after herbicide treatment, cutting, and burns to assess and monitor potential impacts of treatment. If rare species do occur in wetland/area to be treated, hold or relocate species temporarily and release after treatment or particular component of treatment is completed (may want to wait a couple of days when herbicide residue levels may be greatly reduced).