Illegal Pesticide Use is Poisoning the St. Croix Riverway — And the County is Looking the Other Way

The St. Croix National Scenic Riverway is one of the most treasured natural corridors in the upper Midwest. But right now, neighbors along its banks are spraying triclopyr to control buckthorn — and St. Croix County is doing nothing about it.

Triclopyr is sold under brand names like Garlon 3A and Garlon 4. It may seem like a reasonable solution to an invasive plant problem. It is not legal here. Wisconsin Administrative Code NR 118.06(6)(b)3 is clear: within the Lower St. Croix Riverway, herbicide use is limited to direct topical application to cut stems only. Broad spraying is flatly prohibited. St. Croix County is legally responsible for enforcing this. It is not doing so.

This matters because triclopyr is not a benign chemical. EPA’s own scientific review found that it increased breast cancer rates in both mice and rats, caused genetic mutations, damaged kidneys and livers, and produced reproductive failure across multiple species. Its primary breakdown product disrupts fetal nervous system development at concentrations as low as 0.2 parts per million and accumulates in fetal brains at up to four times maternal levels.

The aquatic risks are equally serious. The ester form — found in most residential products — is highly toxic to fish and paralyzes the predator-avoidance behavior of frogs and tadpoles. EPA classifies triclopyr as “very mobile” in soil. In a riverway corridor, there is no safe margin.

Cut the stems. Apply herbicide only to the cut surface. That is what the law requires — and it works.

St. Croix County must enforce its obligations. If it will not, contact the Wisconsin DNR directly.

The history of pesticide safety is a history of broken promises. I worked with National Wildlife Refuges and told land managers that glyphosate was safe. It is not — it has since been classified as a probable human carcinogen. My father worked for the Iowa State Extension Service and told farmers that 2,4-D was safe. It is not — and it is clearly implicated in the cancer pandemic among Iowa farmers. We have been here before. We should know better by now.