TWIN FALLS, Idaho — Bean seed production is big business in Idaho, where the dry climate is a major factor in avoiding disease.
Garden beans can be a bit more sensitive to herbicides compared with dry beans, particularly if certain weather conditions exist at planting. If the soil is cold, bean plants aren’t able to metabolize the chemical, Don Morishita, University of Idaho weed scientist, said during this year’s bean school in the Magic Valley.
To get a read on how individual chemicals affect garden beans, university researchers planted two varieties of garden seed beans and treated them with eight different herbicides.
The trials were designed to compare responses to individual herbicides on each variety by analyzing emergence, injury, stand count and yield.
Researchers planted Caprice and Opus and treated with Eptam 7E, Eptam 20G, Sonolan HFP, Dual Magnum, Basagran 5L, Valor SX, Fierce and Varisto.
The two-year study was funded by the Idaho Bean Commission.
It showed the two varieties responded equally to all the herbicides when it came to stand count. Stand count was down in both varieties in 2017, partly because of weed pressure, he said.
“There was no statistical difference between stand count in 2016 and just a little in 2017,” he said.
Fierce reduced the stand count in 2017, and there were also fewer plants with the Varisto treatment, he said.
As for crop injury, there wasn’t much of an effect in 2016. The only difference is that Basagran resulted in 5 percent crop injury, compared with none in the other treatments.
The big difference in 2017 was that Basagran resulted in 37 percent injury after the first application and 65 percent injury after the second application, but the response was the same in both varieties.
Temperature difference in the two trial years likely contributed to the injury with Basagran in 2017. Temperatures at the end of June were in the 90s for a two week period after the two applications of Basagran, and they were much cooler for the same period in 2016, he said.
The Varisto treated beans in 2017 also had some visual injury from bentazon — one of the two ingredients in Varisto and the same ingredient as Basagram — but not as much as Basagran because there was only one application of Varisto and two of Basagran.
Beans treated with Fierce in 2017 also had some injury, but grew out of it, he said.
There was no statistical difference in yield averaged over all the treatments in 2016. The same held true in 2017, even though stands were lower.
“We concluded both varieties were similar in tolerance,” he said.
Caprice was slightly more sensitive to crop injury than Opus, but the difference was minimal, he said.
Growers want to use herbicides that are consistent year after year, and researchers thought it was important to look at herbicides individually. The next logical step would be testing the effects of tank mixes, he said.