Whitehall Bio Weed Control: Leafy Spurge Flea Beetles

The clustered stems, expanding root system, milky white sap, bright green flowers encased in a yellow-green bract, and narrow leaves are characteristics of one of Montana's notorious noxious weeds, leafy spurge (Euphorbia esula). This species, like many other noxious weeds, is an Eurasian native species. It was most likely introduced to North America via contaminated ship ballasts, and the earliest recorded presence in North America dates back to 1827. This herbaceous perennial is a threatening weed that dominates pastures and roadsides. Its success is partially granted to its ability to reproduce by seed and by spreading its root system, which makes hand pulling it less efficient if you are unable to remove all of its deep roots. Peak germination for leafy spurge seeds occurs around April and May, and the sticky  leafy spurge seeds are able to travel very efficiently through waterways or hitch a ride on humans and other animals. Their seeds are viable for up to 8 years in the soil, making this weed a very difficult one to conquer.

Thankfully, we have two types of very effective biocontrol agents that can help.  We have several species of leafy spurge flea beetles (Aphthona spp.) and the red-headed leafy spurge borer beetle (Oberea erythrocephala).

Two of the more common species of flea beetle are the brown legged leafy spurge flea beetle (Aphthona lacertosa), and the black dot leafy spurge flea beetle (Aphthona nigriscutis) are very strong, capable insects that specialize in consuming this weed and this weed only. The brown legged leafy spurge flea beetle adult has a shiny, black body with reddish-brown legs. The larvae are slender and have an off-white color with a brown head. The black dot leafy spurge flea beetle adult has an orangish-brown body with a black dot near the edge of the wings. Their larvae look almost identical to the brown flea beetle. Both species emerge as adults from the soil in the early summer months to feed on the plant material and mate. The female flea beetles lay their eggs at the stem base or near the roots within the soil. As they hatch, the minute larvae feed on the root system (which does the majority of the damage to the plant) throughout the fall and into the early spring, when they begin to pupate. They easily survive Montana's winters underground, and this cycle repeats itself as those pupated larvae turn into adults that feed on the leafy spurge leaves. 

These two species of flea beetles cause severe damage to the roots, which prevents the plant from taking in proper nutrient levels. They also cause severe damage to the leaves when they are adults. This makes it difficult for the plant to photosynthesize properly. These flea beetles work best on dry, open, hot sites.  They do not work next to ponds, streams or with flood irrigation as the larvae drown. Slowly, as years pass by, you will see a reduction in the prevalence of leafy spurge with the help of the flea beetles. 

The red-headed leafy spurge borer beetle (Oberea erythrocephala) is a slender beetle with long antennae and dark wings, contrasting with their red head. In spring and summer, as temperatures rise, the adults emerge from the soil surrounding the leafy spurge, and after mating, the females lay their eggs (one per stem) near the bottom of the leafy spurge stem. As the larvae grow and hatch, they eat their way down the stem and into the root system of the leafy spurge. They survive through the winter within the root system or within the stem, and they emerge as adults in the spring to start the cycle again. These beetles are fantastic fliers, and we have been able to find them all over Montana. We no longer release them due to their prevalence throughout Montana.

Using biocontrol agents is a slow process; however, it is natural, it is completely safe, and with us, it is completely free (although we do accept donations). Here at the Whitehall Biological Weed Control Project, we collect, study, and rear all sorts of biocontrol agents for weeds like Dalmatian toadflax, yellow toadflax, leafy spurge, spotted knapweed, Russian knapweed, whitetop, and Canada thistle. The season for Dalmatian toadflax insects has ended, which leads us to the season when leafy spurge insects begin to emerge. With that, we will collect them from known sites for redistribution to those of you who could benefit from them. They should be available from late June to mid-July.  These specialized insects know what they are doing, and our goal is to have them help you to the best of their ability. My name is Ava Balough, and you can contact me during normal business hours at 703-870-5696 if you have any questions, comments, or concerns regarding the weeds on your property or the work we do here at this project. The Whitehall Project Coordinator, Mr. Todd Breitenfeldt, is also available during normal business hours at 406-498-5236.