Thistles present challenges throughout South Dakota The "thistle explosion" from last season presents a big challenge for this year, says Leon Wrage, Extension weed specialist at South Dakota State University.
Reports from counties list 1.7 million acres of Canada thistle across South Dakota. This means acres have nearly tripled in 10 years, Wrage said.
Add to that a five-fold increase in perennial sow thistle and a doubling of biennials like musk and bull thistle during the same period.
That puts thistle acres at 2.5 million in all kinds of thistles in South Dakota.
"Fence lines, pastures, roadsides and non-crop areas are the major problem," said Wrage. Acres in non-crop have expanded to about 37 percent of the Canada thistle infestations.
"That is the real problem," said Wrage, "because there is no income from these sites � just expense to control"
"But it is important, because these are seed sources for cropland and wetland areas," said the specialist.
"Weed fighters have done a good job in field crops. Very effective controls are on the market in small grains, soybeans and corn, and the big factor is that these control technologies are being used," said Wrage.