Warm winter, early spring increase risk from noxious weed

Ohio's warm winter and early spring mean that cressleaf groundsel is on the rise earlier than normal and has the potential to cause problems for livestock producers, says an Ohio State University Extension beef cattle expert.

The weed is now listed on Ohio's Noxious Weed list because of the poisonous characteristics it poses to some animals.

In fact, Ohio farmers are seeing more cressleaf groundsel than ever before, said Stan Smith, an OSU Extension program assistant in agriculture and natural resources. The unusually warm winter led to an early spring and has caused many biennial and perennial plants to get started several weeks ahead of normal

Winter 2012 was the warmest winter experienced nationwide since 2000 and the fourth-warmest winter on record, according to the National Oceanic and Atmospheric Administration. It occurred because the jet stream, which divides the cold air to the north from the warm air to the south, settled at a much higher latitude this year, the federal agency said.

And while cressleaf groundsel has become an increasing problem in minimum and no-till row crop fields and also in aging hay fields with less than acceptable stands, this year Smith said growers and producers are seeing much of it because the weed grows very well in multiple environments - including saturated soils.

"We've had cressleaf groundsel for about six to eight years but it's much more prevalent this year, especially in pasture fields damaged by trampling from last summer's record rainfall, which allowed weeds to fill in those spots," he said. "Then with the early spring weather in March, the weeds got off to a great start, a few weeks earlier than normal.

"We're seeing it in pasture fields, in row crop fields that haven't been planted yet and in hay fields where the stands have thinned. Cressleaf groundsel reproduces only from seeds and each plant produces many, probably hundreds of thousands seeds that are easily transported by the wind."

Cressleaf groundsel is a biennial. The plant is a member of the Aster/Composite family and is also called butterweed, yellowtop, golden ragwort, and yellow ragwort, Smith said.

The concern is that nearly all species of groundsel, which emerges in the fall and flowers in the spring, are considered a potential toxic plant because they contain pyrrolizidine alkaloids (PAs), which are metabolized in the liver to other compounds that are toxic, primarily to liver cells.

"The PAs are found in the plant throughout the growing season but appear to be at their highest levels when the plant is in the bud to flower stage," he said. "The flowering portions of the plant and the youngest tissues generally contain the highest concentrations."

Poisoning usually occurs as a result of consumption of the plants over several days to several months, Smith said.

"Because the effect on the liver is cumulative, signs of poisoning can occur weeks to months after livestock have begun consuming cressleaf groundsel," he said. "Poisoning is caused by liver degeneration and failure.""

While livestock typically don't eat cressleaf groundsel, if their other grasses are eaten down, they may eat it, Smith said. Livestock can also ingest it easily through hay bales chopped or processed into rations.

"If a horse consumes 5 percent of its body weight in the toxin, it could be fatal, typically due to liver failure," he said.

Producers should look for affected animals to show depression and loss of appetite initially, followed by neurological signs with head pressing, aimless walking, incoordination, and rectal straining, Smith said.

Another concern is that PAs are not destroyed by the hay-making and curing process, he said.

"Ensiling of forages may reduce the concentration of PAs, but will not entirely eliminate them," Smith said. "One way to avoid concerns with cressleaf groundsel in the future is to consider re-seeding hayfields with thin stands."

Sheep have also been used in some areas to control the plant because the animals are considered more resistant to the effects of PAs than cattle and horses.

But, he cautioned, sheep are susceptible to poisoning if they consume sufficient amounts.

More information on identifying cressleaf groundsel can be found at http://ohioline.osu.edu/b866/b866_12.html . And more information on how to control this plant can be found at http://www.drovers.com/sites/default/files/Cressleaf.pdf

OSU Extension Educator Jeff McCutcheon also discusses current cressleaf groundsel concerns in this short video: http://go.osu.edu/GROUNDSEL

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