Johnson County landowners have treated an estimated 7,607 acres of noxious weeds in the past year, resulting in a decrease of the pesky musk thistle.

More work, however, remains with almost 16,700 acres still untreated with increased infestations of three other prevalent noxious weeds in the county.

These were the key findings in two reports submitted Thursday, April 28, to the Johnson County Board of County Commissioners by James Hoge, the county’s noxious weed director since 2005 at the Johnson County Department of Public Works. His main duties are to control, manage and eradicate noxious weeds that have infested thousands of acres in mostly rural areas of the county.

On Thursday, Hoge’s 2021 Annual Noxious Weed Eradication Process Report and the 2022 Johnson County Annual Noxious Weed Management Plan were unanimously approved by the BOCC. Both reports are required annually by the Kansas Department of Agriculture.

Johnson County’s infestations involve four of the 14 noxious weeds now identified by the Kansas Legislature. The state began identifying and eradicating certain prevalent noxious weeds under a law passed in 1937.

Noxious weeds are invasive and harmful to the environment, natural resources, crops and agriculture, other plants or wildlife. Common yard weeds, such as dandelions, henbit, clover, etc., are not considered noxious.

“They’re simply a nuisance when they pop up where they’re not wanted,” Hoge said with a smile.

In the 2021 eradication progress report, Hoge estimated 16,695 acres, including both public and private land, still had infestations of noxious weeds, presenting an increase of approximately 9% in the past year.

“Increases in acreage are the result of extremely wet conditions during the spring and early summer followed by temperatures about 90 degrees during July and August, all of which prevented timely herbicide applications,” Hoge advised the Board in a briefing sheet accompanying his report.

Johnsongrass was the county’s main noxious weed, affecting an estimated 6,731 acres, an increase by 12%. Despite its name, Johnsongrass is not native to Johnson County. It is named after Colonel William Johnson, who first planted the grass, now considered a very invasive weed, on his farm near Selma, Alabama, around 1840.

Sericea lespedeza had the largest percentage of increased infestation, involving 4,603 acres and representing a spike of 46%. According to Hoge, identification of Sericea lespedeza is “extremely difficult and had been under reported in previous years,” resulting in more infested acreage.

Musk thistle, which traditionally had been the county’s main noxious weed in previous years, had a 12% decrease to 5,128 acres, reflecting additional herbicide treatment of infested acreage. Field bindweed was found in 233 acres, an increase of 7%.

Noxious weeds are found throughout Johnson County, including on county-owned land, such as right-of-ways of roadways and public utilities, like sewers; in fields near runways of the two county airport complexes in Olathe and near Gardner; and on property belonging to the parks and recreation district.

Efforts to manage, control and eradicate noxious weeds usually begin in early-to-mid-spring before the growing season of the plants and last until late August and early fall to inhibit seeding from the unwanted weeds.

The county’s Noxious Weed Program operates out of the Public Works complex at 1800 West Highway 56, Olathe. It includes selling herbicide-controlling chemicals to residents of Johnson County solely for use on land in the county. The products can only be purchased for noxious weed control.

The Noxious Weed Office is open Monday through Friday from 6:30 a.m. to 3 p.m. The number is 913-715-8358. Find more information about noxious weeds and controlling efforts.