Moscow, Idaho
August 5, 2009

A new computer program developed by University of Idaho weed scientists is designed to simplify herbicide selection and prevent development of herbicide resistant weeds and damage to future crops.

Weed scientists Donn Thill, Joan Campbell and Traci Rauch developed the program for dryland farmers in northern Idaho, eastern Washington and eastern Oregon. Weed scientist Don Morishita at the Kimberly Research and Extension Center is working to expand the program's use to southern Idaho irrigated crop rotations.

"The goal is to help growers make decisions about which herbicide might best control weed problems and fit into their crop rotations," said Thill, a professor of weed science and superintendent of the Palouse Research, Extension and Education Center at Moscow.

The program, "Herbicide Resistance and Persistence Management,” is available on a free trial basis to growers. Growers who decide to use the program will be charged a $50 annual subscription fee to cover updates.

The program combines two of the College of Agricultural and Life Sciences' most popular publications into a dynamic program that can provide more frequent updates than printed offerings, Thill said.

Tracking and adjusting herbicide use is essential to controlling resistance in weeds. Over 200 weeds worldwide now show resistance to commonly used herbicides. Thill and Campbell have been leaders in helping Northwest growers plan strategies to limit herbicide resistance in weeds.

The main way to avoid resistance is to change herbicides based on their modes of action on weeds.

Growers can face substantial challenges in both trying to use herbicides from different groups to control common weeds and then keeping clear records through multiple seasons.

The University of Idaho's herbicide management program can help accomplish both tasks.

In addition, the program targets another challenge for growers, deciding which herbicide best fits their crop rotations. Some herbicides can persist in the soil for more than a year in concentrations high enough to damage future crops that are especially susceptible to damage.

The backbone of the program is manufacturer's labels required by federal law for all herbicides. The label information contains directions on which crop the herbicide is registered and directions on how to use it.

The program's data files contain all herbicides and their uses in Pacific Northwest dryland, or non-irrigated, agriculture that have been registered by the U.S. Environmental Protection Agency, a massive undertaking. Multiple crops and rotations made a computer program the best option for growers, Thill said.

The database tracks label directions on herbicide persistence for up to five years, although in most cases the effects are gone in a year. Some crops, however, can suffer herbicide injury several years later. In rare instances, Thill said, unique soil conditions could extend herbicide persistence but common sense made five years seem a logical limit.

Thill said the weed scientists plan to update the database twice each year to keep the data as current as possible. The program is available for purchase online at www.cals.uidaho.edu/herbicidemanagement. Growers who download the program will have a six month trial period before they have to pay a subscription fee.
The program's development was funded by the Idaho Wheat Commission, Idaho Barley Commission and University of Idaho College of Agricultural and Life Sciences.

Written by Bill Loftus

Website: http://www.uidaho.edu

Published: August 5, 2009