County’s Integrated Vegetation Management Plan sees reduction in use of applied herbicide

Posted on: July 12, 2018


Lanark County is seeing results and a reduction in herbicide use as part of its long-term efforts to control noxious weeds, such as wild parsnip, through its Integrated Vegetation Management (IVM) Plan.

Due to wild parsnip’s rapid expansion along the county road system, the county has chosen to actively control the phototoxic weed that causes blisters and burns.

“Controlling wild parsnip maintains the safety of anyone who must enter the roadside, including motorists involved in an accident, road workers, emergency/first responders, volunteers removing litter, and the public,” explained Lanark County CAO Kurt Greaves. “From an agricultural perspective, infested pastures pose a health risk to livestock, as the chemicals in wild parsnip cause weight loss and infertility issues. Infested hay cannot be sold as fodder for livestock and infested crops are not salable as food-grade quality or as seed.”

Controlling invasive roadside vegetation also has environmental benefits, including stopping the spread of invasive species, protecting conservation areas, reducing damage on adjacent agriculture and re-establishing native pollinator habitat.

Prior to the roadside spraying program, the county attempted to mechanically control wild parsnip by tailoring mowing practices to reduce seed production. However, mowing was not an effective control, as it removes all vegetation, weakens competing plants and does not eradicate the wild parsnip roots and seeds.

“Peer-reviewed papers on the biology of wild parsnip indicate the ideal mowing time is very narrow and dependent on individual growing conditions, making mowing as a control measure difficult,” explains Michelle Vala, Lanark County Vegetation Management Intern. “This prompted the county to develop an Integrated Vegetation Management (IVM) Plan and use a multifaceted approach to managing the wild parsnip.”

Lanark County engaged two highly qualified experts at CVI IPM Services to develop an IVM Plan, which is successfully guiding the county not only with wild parsnip, but with the control of other noxious and invasive plants. Modifications are continually made to the IVM Plan as the county becomes aware of improvements. The IVM Plan outlines the best approach to manage the wild parsnip based on the level and extent of infestation. Heavy infestations throughout the county and a lack of success from mowing resulted in the county opting to use a selective herbicide to reduce the infestation.

In 2016, the roadside spraying program began with a broad application technique of herbicide to reduce the infestation. In 2017, a spot-spraying method was used that required a licensed applicator to walk the road allowance and spray individual wild parsnip plants. The county treated more roads in 2017 than 2016, but spot spraying still reduced the amount of herbicide used by 55 per cent.

In 2018, the county increased the amount of roads spot sprayed even more, reducing the amount of herbicide used from 2016 to 2018 by 70 per cent. “We plan to continue the trend of decreasing herbicide application as the number of roads requiring herbicide treatment decreases,” Ms. Vala explains.

Meanwhile, manual control measures have been increasing as the wild parsnip infestation levels return to a manageable level. Roads with sparse wild parsnip plants are dug up by hand and many patches are cut or mowed instead of sprayed.

“Lanark County is committed to eliminating herbicide usage as the infestations become manageable by using manual control measures, such as digging, cutting and mowing. This is outlined in the IVM Plan,” Ms. Vala says.

If you would like more information about Lanark County’s IVM Plan, please visit the county’s website at or call 613-267-1353.