There was an article in EntomologyToday recently about new data which shows Japanese Barberry (Berberis thunbergii) harbors the Blacklegged Tick (Ixodes scapularis) which carries Lyme Disease. I have a good friend who suffers from the ravages of Lyme Disease, and I’ve other friends who also have been affected by this horrible disease, so I thought this would be a good story to investigate.
A study conducted by a team led by Scott C Williams, PhD at the Connecticut Agricultural Experiment Station concluded that clearing away the growth of Japanese Barberry every five years reduced tick abundance to a level nearly equal to the levels of non-barberry plots. The tick has a two-year life cycle, so the reduction doesn’t occur until the third year after the growth of the barberry has been removed. But then it lasts through year five. So by maintaining a five-year management cycle, the near elimination of this tick should be achievable.
Although Williams work was limited to Japanese Barberry, he suggests the same type of management might be warranted for other non-native plants such as ferns, burning bush or huckleberry — all of which provide the same type of “humid microclimate” which favors Blacklegged Tick survival.
Non-Native Japanese Barberry (Berberis thunbergii)
Japanese Barberry was introduced from Japan in the late 1800s because it was deer resistant due to its thorny exterior and because it thrives in most ecosystems. Unfortunately, besides its relationship with the Blacklegged Tick, it also plays well with non-native earthworms which leave the soil depleted for native plants, but adaptable more non-native Japanese Barberry.
White-Footed Deer Mice and other rodents are the principal carrier of the Lyme Disease tick because they nest under this barberry. However, even though deer do not eat the shrub, ticks will often hitch a ride as the deer walk by and that is why deer are blamed for spreading Lyme Disease.
Don’t be fooled into purchasing “sterile” species of non-native barberry. It is generally impossible to guarantee a plant is 100% sterile.
Native Alternatives to Non-Native Barberry
There are many lovely native shrubs to choose in place of the non-native barberry. How about trying Winterberry (Ilex verticillata), Golden Currant (Ribes aureum), Chokeberry (Aronia spp), Virginia Sweetspire (Itea virginica), New Jersey Tea (Ceanothus americanus) or American Holly (Ilex opaca) — just to name a few. Find more alternatives in Charlotte Adelman’s book Midwestern Native Shrubs and Trees: gardening alternatives to nonnative species.
Here’s a good fact sheet on Japanese Barberry by the Michigan Department of Natural Resources.