Non-herbicide Control Options for Managing Leafy Spurge

By Alanna Jonson, Agri-Environmental Specialist, Swift Current

November 2024

Leafy spurge is an aggressive, introduced perennial weed that impacts Saskatchewan rangelands. The plant can form dense stands, reproducing from both the seeds and the extensive, creeping roots. These deep roots can put out new lateral growth which makes the plant difficult to control once established. Leafy spurge contains a white latex sap that can irritate skin and is toxic to some livestock. Once established, leafy spurge can significantly reduce the overall productivity of a pasture by causing livestock to avoid certain areas and choking out desirable vegetation.

Selecting the best control option depends on the size of the population and the desired outcome. For small patches of weeds, it may be possible to eradicate the plants, completely removing them from the pasture. Early detection of young plants through regular pasture scouting is one way to help prevent the establishment of new populations. With larger populations, an integrated approach to weed management could contain the area, avoiding further spread and gradually reducing the number of plants. Selecting a control option depends on the size and density of leafy spurge patches. Two control options are targeted grazing and biological control.

Targeted grazing of leafy spurge uses small ruminants to browse leafy spurge plants. Sheep and goats are less affected by the compounds in leafy spurge, making them ideal candidates for grazing the weed. Targeted grazers with experience in grazing spurge can manage their animals by focusing grazing efforts on high density areas. This approach damages the above ground growth, reduces the likelihood of the plants setting seed, and decreases the plants’ energy reserves. This may require multiple treatments per year but over time it can reduce the number of weeds to more manageable levels. The Resilient Agricultural Landscapes Program is one source of funding to support producers with eligible targeted grazing projects.

Biocontrol using insects is another option for reducing large infestations. There are several insects that feed on leafy spurge, but flea beetles have been some of the most successful in Saskatchewan. The beetles produce larvae which feed on the roots of the plants. There are multiple species of beetles that are adapted to different conditions - some prefer hot dry sites while others prefer different soils. Releasing the beetle best suited to the conditions can improve their establishment and effectiveness. Spurge hawk-moths are another species that can be seen feeding in some areas of the province. These showy insects can eat some of the vegetation but aren’t usually effective at controlling the plants on their own. They are best used in combination with other insects.

Not all control options are effective in the same place at the same time. For example, if you are releasing beetles in a large patch, you may want to limit herbicide applications to small perimeter patches to avoid further spread while still giving the beetles a chance to do their job. It is important to consider how different control options interact to avoid unnecessary costs and increase the chances of success. For more information on integrated weed control options, keep an eye out for the upcoming rangeland weed control series in February. Registration for these events will be available through the online agriculture events page.