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Beetles offer effective weed control

With the help of the
weed-eating flea beetle, researchers significantly reduced infestations of a
non-native plant, leafy spurge, on Montana rangeland. The good news is that
this biological method of weed control worked effectively over the course of a
9-year study. The bad news is that rather than native plants returning to
flourish in the absence of leafy spurge, other non-native species became
dominant in its place. 

The study,
presented in the current issue of the journal Rangeland Ecology & Management, sought to evaluate the
responses of native vegetation once the invasive species was removed using
classic biological control. Black and brown flea beetles have previously been
used successfully as biological control agents to manage leafy spurge on a
large scale.

In the current study, the
weed-eating flea beetles were released in 1998 in southeastern Montana on
privately owned land used for cattle grazing. About 6,000 flea beetles were
introduced onto 32 plots of leafy spurge, while 20 more plots went untreated.
Over time, the beetles dispersed to the untreated plots, suppressing leafy
spurge there as well.

By the study’s end in 2006,
leafy spurge foliar cover was reduced 80% to 90% compared to 1998 assessments.
While other vegetation did increase once this invader was controlled, another
non-native plant, Poa spp., became the dominant species.

Once established, strong
invaders like leafy spurge may make the native plant community more susceptible
to invasion by other non-native species. Any new infestations should be treated
as soon as possible to reduce long-term effects such as contributions to the
seed bank, native species loss, and ecosystem modification.

By Jack L. Butler, Stefanie
D. Wacker

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