Flea beetles might be the best way to control leafy spurge, a state-level noxious weed which can be found in nearly every corner of the state, according to Pete Bauman, SDSU Extension range field specialist.
"By far, the most successful biocontrol agents for leafy spurge in South Dakota have been the leafy spurge flea beetles," said Bauman. "Landowners are obligated to control noxious weeds, and the best strategy for weed control is an integrated pest management (IPM) approach."
Flea beetles control leafy spurge through foraging on the roots as larva and through foraging on the host plant as adults. Flea beetles are generally collected by hand via simple sweep nets in late spring and early summer prior to the female beetles laying eggs in order to have females lay eggs at the new release site to build a new population.
Over the last 20 years, many state, federal and private organizations have worked closely with landowners to collect and distribute flea beetles for leafy spurge control and to establish a series of 'insectories' on private and public lands for future collection and redistribution.
"The benefits of utilizing biological control in an IPM system for leafy spurge are clear," Bauman said. "Successful biological control can dramatically reduce populations and input costs in labor and chemicals while retaining pasture plant community diversity by reducing or eliminating non-target chemical impacts to desirable native broadleaf plants such as native flowers and legumes."
Biological control, Bauman explains is simply utilizing a natural enemy of the host species to attack and control the host. In this case, the enemy is the flea beetle and the host is the spurge plant.
Bauman added that labor and monetary savings can then be invested into overall pasture management, including managing the biocontrol program by annually moving biocontrol agents into the pasture.
Establishing a Successful Leafy Spurge Biological Control Program
Biocontrol is a proven method of managing spurge populations. However, not all biocontrol programs meet with immediate success, and in certain cases biocontrol with flea beetles simply will not work.
"Biocontrol requires that the spurge beetles have a population of spurge to feed on, thus the beetles will never completely eliminate spurge in the pasture," Bauman said. "Rather, biocontrol is aimed at reducing the leafy spurge population to an acceptable level. It can take as little as one year or as many as six years for a released population to firmly establish and significantly impact the spurge, with three to five years being common.”
Today, the South Dakota Department of Ag in partnership with county weed supervisors coordinate the majority of public collection and redistribution of leafy spurge flea beetles.