ECO products work on insects using a unique mode of action which has no effect on mammals. Here is the "short" explanation…

ECO products like their ECO LAWN GRANULES use plant oils for their active ingredient. This active contains compounds that are similar to octopamine. Octopamine is kind of like adrenaline controlling insect functions like metabolism, movement and heart rate. Since mammals, bird and fish do not have octopamine receptors, ECO has no impact anything other than insects.

When insects come in contact with the octopamine, it effectively clogs and blocks their neurorecptor sites which in turn causes them to die. The end result is a reduction in the local insect population without any impact to the other surrounding life.