In the social sciences, they call it unintended consequences, in the military, collateral damage — good intentions gone awry.

In row-crop farming, there is no technical term for it, but the effects always work out the same way: higher input costs, coupled with added work and worry for producers.  

Whatever one chooses to call it — unintended consequences or collateral damage — horseweed is a case of a good intention gone awry.

In the decades when conventional tillage practices were the norm rather than the exception, horseweed was never a problem. A winter annual, it germinated in fall, grew during the winter and produced seed during the spring and early summer.

The windblown seed that nature had equipped to germinate on the soil surface was easily eliminated through conventional-tillage.

The problem started when minimal-tillage cropping systems were introduced roughly a generation ago both as cost-saving measure and as a strategy for building up organic residue. Minimal-tillage provided the optimal conditions in which horseweed seed could germinate and grow.  

Michael Patterson, an Alabama Cooperative Extension System weed scientist and Auburn University professor of agronomy and soils, remembers the first time he encountered horseweed problems in 2003 on cotton acreage located a few miles west of Decatur.

He was accompanied by his colleague Charles Burmester, a Tennessee Valley-based agronomist who had first inspected the field and invited Patterson up from Auburn University to take a closer look.

“It was a cotton field just covered with horseweed,” Patterson recalls. “The cotton was planted and was up about 3 or 4 inches, while the horseweed was standing at between 6 and 8 inches.”

Fortunately for the producer, extensive cultivation, reinforced with a few herbicide applications, brought the horseweed under control.

“He got a handle on it, but it caused him some grief,” Patterson says.

This marked the beginning of a recurrent theme throughout north Alabama, Patterson says. Alongside the far more virulent Palmer pigweed, horseweed rates as a comparative lightweight.

A few herbicide sprayings, and in worst-case scenarios, cultivation, usually stops these weeds in their tracks before they can pose serious threats.