Ecological Mystery Unravels, With Toxic Pesticide Use at the Center

May 12, 2021 | In 2021, a team of scientists published in Science a piece that appears to solve an ecological mystery that had persisted for decades. Throughout the southeastern U.S., bald eagles and other top-level avian predators were experiencing mass deaths from a disease known as vacuolar myelinopathy (VM), a neurological ailment that causes lesions in affected animals’ brains. Scientists identified the source of the exposure as a cyanobacteria growing on an invasive weed, but up until now, did not know how the bacterium caused disease. Now, scientists have determined that the chemical bromine, likely introduced by brominated herbicides in an attempt to manage invasive species, is the trigger for the production of the cyanobacteria’s neurotoxin. While there are several sources of bromine (flame retardants and other industrial compounds, including fracking pollution) one of the most likely sources is the pesticide diquat dibromide. Pesticide products containing diquat dibromide are often applied in chemical-intensive control of hydrilla. [Breinlinger, Steffen et al. Hunting the eagle killer: A cyano- bacterial neurotoxin causes vacuolar myelinopathy. Science. 371(6536), 2020.]