Instituting a management plan for Leafy Spurge (Euphorbia esula) is complicated. Spurge not only has toxic sap, making it unappetizing to most grazers, it also exudes a toxic chemical into the soil to reduce competition from other plants. Controlling this aggressive pest is not easy in the best of circumstances, and with a big head start on the AFFI landscape, it’s really well established here. We’ll have to access the complete Integrated Pest Management (IPM) toolbox to make a dent in the population of this hardy European invasive.
Since total removal of an established spurge patch is next to impossible, biological control agents can be used to reduce the strength of the population so that other plants can grow amongst it. There are numerous European spurge-eating insects that have been widely released in North America with varying degrees of success in controlling Leafy Spurge. For example, the larvae of Leafy Spurge beetles (Aphthona spp) feed voraciously on spurge roots, weakening the plants and sometimes killing them. This last weekend I had the pleasure of learning and working alongside Mae Elsinger, Range Biologist with Agriculture & Agri-Foods Canada, as we collected Leafy Spurge Beetles in Spruce Woods Provincial Park for transfer to the AFFI parcel.
Mae and I spent a hot Saturday afternoon out on the ranges with Fire Marshall Henry Booy, who has worked for over 15 years to manage the spurge population on native prairies in Spruce Woods. Henry sure knows his local beetle populations, and we had great success in the day’s venture. Early July is the right time to collect beetles; they have just completed mating and females are pregnant and ready to lay eggs on Leafy Spurge plants. After hatching, the larvae will tunnel underground and attach themselves to roots to begin feeding and growing.
The work plan was simple … using a sweep net we marched along sweeping back and forth across the vegetation in patches that Henry knew to contain beetles. After ten or fifteen minutes of this, we’d head back to the vehicle and dump the insect contents of our nets into a collection apparatus, where the tiny beetles would eventually fall into a jar in the bottom. They were then tapped out into vials and placed in a cooler for transport. We kept at it for five hours or so and finally called it quits around 4:00 PM. The total? … more than 15 thousand lovely little spurge eaters!
Arriving back home in Brandon, Mae and I proceeded out onto the food forest to the sites we had previously identified. There, we released the little creatures in clusters of approximately 2000, allowing them to disperse at a rate of their own choosing. It will be fun to sample for beetles with sweep nets in future seasons to see how they’ve done. If we find lots of adults, we can collect and disperse them further around the parcel. Our landscape may also become a source of beetles for other spurge control efforts in the Westman area.
Next steps? Management by fire is another method to attack Leafy Spurge. More on that in the next blog …
See you out on the trails!