Most organic weedkillers are only able to burn off the foliage of pest plants. Coconut fatty acids for instance are used in organic spays and are able to rapidly dessicate leaves but have little of no systemic effect on the root system of the plant which will regrow. The toxicity is low for birds and mammals.
"However, Potassium salts of fatty acids are relatively selective in toxicity based on the insect species and stage of development. Soft bodied insects such as aphids, whiteflies, and mealy bugs are more susceptible to desiccation. The least affected are flyingadult insects with more durable exteriors, such as ladybird beetles. However, insects in the immature, flightless stage ofdevelopment are more vulnerable to this active ingredient."
Coconut fatty acids are also quite high to aquatic invertebrates
"Potassium salts of fatty acids are highly toxic to aquatic invertebrates. The LC50 was determined to be 0.57 ppm in a 48-hour acute toxicity study with Daphnia magna. The EPA requires all product labels containing this active ingredient to state that the product is not to be applied directly to water and the user is not to contaminate water bodies by cleaning equipment"
The MSDS of commonly used Coconut fatty acid for roadside spraying states toxicity ratings of 6.3A, 8.3A, 9.1C. In comparison the glyphosate used in Cut'n'Paste with a 9.1D (lower toxicity than 9.1C) toxicity rating is only slightly toxic to aquatic organisms and being in a gel form is unlikely to have any effect on insect larvae, soil or water organisms.
One wonders about the wisdom of using organic weedkillers for roadside spraying under the impression that they are less toxic and therefore present less risk to the environment.
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