A mostly dry, windy spring gave weeds some advantages as crop-growing season got underway in southern Idaho and southeastern Oregon.
“One of the problems we had was the wind,” said Brent Zeyer, a retired Melba, Idaho, farmer who helps son Tad with operations. “We couldn’t put out post-emergent herbicide on the schedule we wanted to.”
They since have caught up, he said.
Joel Felix, weed-management researcher at the Oregon State University Malheur Experiment Station, said dry, windy conditions slowed onion farmers’ weed management soon after planting.
Wind delayed spraying. And in dry soil, an herbicide applied in the late pre-emergence stage did not get the moisture it needed to activate. Weeds in turn emerged. These growers thus had to wait until onions reached the two-leaf stage before applying another chemical, he said.
“By and large they have caught up,” Felix said. “Except now, Yellow Nutsedge has come up and they are using an herbicide through drip irrigation to control it.”
Albert Adjesiwor, weed scientist at the University of Idaho Kimberly Research and Extension Center, said pre-emergent herbicides in dry soil not only can lack the soil moisture they need to activate, but, “if it is dry and windy, those herbicides are going to be lost very fast from soil.”
And post-emergent herbicides won’t kill weeds as effectively as they would in normal conditions, he said.
Farmers who have limited options to use a pre-emergent, because the soil is too dry, can wait and apply a post-emergent “hoping there are some good conditions, Adjesiwor said.
But relying only on post-emergent herbicides increases the chances that weeds will escape the farmer’s control, he said.
“Weed escapes are a recipe for disaster,” Adjesiwor said. Challenges include the immediate work as well as increased future risk the weed will develop resistance to the herbicide, produce seed and escape again.
Adjesiwor said dry soils leave fewer soil microorganisms to break down herbicide, which can limit planting options the following year.
Roger Batt, statewide coordinator for the Idaho Weed Awareness Campaign, said overall weed pressure hasn’t changed much from 2020 to this year. But late-May rains, followed by heat, “are going to result in some new growth and some added weed pressure,”
Some species are thriving more.
“We do see a lot more Kochia,” Batt said.
As for noxious weeds, Poison Hemlock “is out in full force” and the recent rain prompted puncture vine to emerge, he said. Whitetop, or Hoary Cress — equipped with horizontal and vertical root system and now nearing its last blooming stages — will seed for next year if not controlled. Morning Glory, or Field Bindweed, also has a troublesome root system.
“We’re also starting to see Rush Skeletonweed,” Batt said. It’s hard to eradicate, crowds out native vegetation and has no nutritional value — significant in that it causes grazing and other animals to move to other areas.
Salt Cedar or Tamarisk also is appearing, he said. It’s a high-volume consumer of water, a potential problem in a dry year.
June 04, 2021 at 10:15PM
https://www.capitalpress.com/ag_sectors/research/weeds-flurish-in-dry-soils-of-southern-idaho-se-oregon/article_1504fd30-c4c0-11eb-ba6d-072c45e087b0.html
Weeds flurish in dry soils of southern Idaho, SE Oregon - Capital Press
https://news.google.com/search?q=dry&hl=en-US&gl=US&ceid=US:en
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