The Strange Case of Barberry, Ticks, and Earthworms

By Susan Littlefield

We've all probably heard about the problems caused by invasive plant species crowding out native vegetation and altering the ecosystem. But new research has shown that at least one invasive species is affecting the natural environment in unexpected ways and some of those changes may even be having an impact on human health.

Tom Worthley, assistant extension professor in the Department of Extension in the College of Agriculture and Natural Resources at the University of Connecticut, along with colleagues Scott Williams, adjunct professor in UConn's Department of Natural Resources and the Environment, and Jeffrey Ward, from the Department of Forestry and Horticulture at the Connecticut Agricultural Experiment Station in New Haven, are looking at ways to return the ecosystem of the University of Connecticut Forest in Storrs, now overrun with invasive Japanese barberry (Berberis thunbergii), to a more natural state.

In the process, they discovered that barberry has a negative impact on the forest ecosystem in some surprising and unexpected ways. It turns out that barberry provides the perfect humid environment for the ticks that carry Lyme disease and other tick-borne diseases. ″When we measure the presence of ticks carrying the Lyme spirochete (Borrelia burgdorferi) we find 120 infected ticks [per acre] where barberry is not contained, 40 ticks per acre where barberry is contained, and only 10 infected ticks where there is no barberry,″ says Scott Williams. And the barberry also provides a favored environment for mice, which act as vectors to spread the immature nymph stage of the ticks.

The introduced barberry also creates the perfect conditions to promote the spread of another introduced species that has a negative impact on forests -- the earthworm. Most folks are surprised to learn that earthworms are not native to northern regions of the U.S., including New England. The introduced worms gobble up the forest leaf litter, leaving the soil exposed. Says Jeffrey Ward, ″These worms have big appetites and when the litter layer gets eaten we see gullies forming, sediment washing into streams, soil chemistry changing -- all sorts of negatives that you don't see in a healthy forest ecosystem.″

To combat these problems, the researchers are working on developing practical and effective ways to control Japanese barberry in forested areas, including carefully targeted flame weeding.

To read more about this research, go to: UConn Today.

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