May 17, 2006
Weed specialists: Yellow fields running up red flags for farmersWEST LAFAYETTE, Ind. "Yellow fever" has broken out in farm fields across Indiana.
A bright, butter-colored weed is casting a beautiful hue over many fields and pastures. Unless farmers act quickly this spring, however, that beauty could turn into a beast, said Purdue University weed scientists Glenn Nice and Bill Johnson.
"What we're seeing in Indiana is a plant by the name of cressleaf groundsel, also known as butterweed," Nice said. "The plant is a winter annual weed. It comes up in the fall as a rosette and, in the spring when temperatures are right, it bolts and turns into the yellow plant that you see in the fields today."
Cressleaf groundsel is a troublesome weed for farmers, especially when it takes over fields like is has this year, Johnson said.
"Although it looks very pretty, it actually creates tremendous problems for producers in the spring in getting their crops planted," Johnson said. "This weed helps keep the moisture locked into the soil and is very difficult to control with most postemergence herbicides once it has started flowering.
"Many growers are now left with using tillage in order to get the ground prepared for planting their crops. This results in additional trips across the field, possible soil compaction and, ultimately, delays planting dates and causes growers to lose some yield because of the later planting dates."
Cressleaf groundsel populations are up this year because recent wet weather kept many farmers from making spring herbicide applications. Some farmers also did not treat their fields with herbicides this past fall a strategy that could have prevented the weed outbreak.
"There's really only a couple of things that a grower can do right now," Johnson said. "One thing would be to apply a paraquat-based herbicide program with 2,4-D and a triazine herbicide. That program is probably going to give you the quickest desiccation of the above-ground weed biomass.
"The other thing a person can do is use a glyphosate-based program. They need to use at least 1.5 pounds of acid per acre and utilize 2,4-D. That's going to result in a little bit slower desiccation of the weed biomass but will also provide control for a broad spectrum of weeds, as well."
Farmers also can till their fields, Johnson said.
"They could disk the field when it's dry enough, but that's probably the least desirable strategy from the standpoint of managing soil compaction and erosion," he said.
Growers likely will have to use tillage at some point anyway in order to run a planter through the weed debris that will be sitting on the soil surface, Johnson said.
Cressleaf groundsel can be a problem for livestock, too. The weed is among the toxic Packera species, Nice said.
"This species can be toxic to cattle and horses," Nice said. "Cressleaf groundsel, although not as toxic as its cousin to the West, tansy ragwort, can still produce toxic alkaloids. Poisoning is most often chronic, taking several weeks for symptoms to appear. Symptoms in cattle can range from scaly noses and rough coats to listlessness and a decreased appetite with digestive problems.
"In severe cases, cattle may be jaundiced and/or photosensitive. Calves can develop swollen jaws, while horses can become nervous and have 'sleepy staggers' where they bump into objects or become entangled in fences. Long-term exposure can cause liver damage."
Farmers can take steps this fall to prevent another cressleaf groundsel invasion next year, Johnson said.
"There's a lot of value in fall-applied herbicides for managing this weed," he said. "Treatments containing glyphosate and/or 2,4-D are very effective."
For more information on cressleaf groundsel and control options, read Purdue Extension information sheets "What Do We Do About the Yellow Weeds?" and "Cressleaf Groundsel and Indiana," both written by Johnson and Nice. The publications are available by logging onto the Purdue Weed Science Web site and then clicking on the articles under "Weed Science News and Notes."
Writer: Steve Leer, (765) 494-8415, firstname.lastname@example.org
Sources: Glenn Nice, (765) 496-2121, email@example.com
Bill Johnson, (765) 494-4656, firstname.lastname@example.org
Note to Journalists: Other farm-related story ideas are available at Purdue Agriculture's Farming 2006 Web site
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