Strategies for Lyme disease prevention have ranged from mass deer culls to widespread spraying of public parks but in Oxford, Connecticut, a new tactic is being used: the removal of Japanese barberry from forested areas. Could the eradication of this invasive plant species be an effective way to reduce cases of Lyme disease? A new study suggests that it is.
Starting on August 12th, a team of eight from AmeriCorps, led by Tom Adamski and Susan Purcella Gibbons from the Oxford Conservation Commission, worked for three days to remove strands of Japanese barberry from an area of land at Rockhouse Hill Preserve. This, according to research by scientists at the Connecticut Agriculture and Experiment Station (CAES), Jeffrey Ward and Scott Williams, can reduce the presence of Lyme disease-carrying ticks by some 80%.
Lyme Disease Landscaping
Such a short, intensive, project cannot eradicate all of the barberry on the land but it may have a significant impact and encourage others to take similar action on their own property, thus lowering the Lyme disease burden farther afield. Japanese barberry is one of many invasive plant species not native to the area and such plants can decrease biodiversity which, itself, has been recently associated with the incidence of Lyme disease. Removing such invasive plant species can help local flora (and fauna) reassert itself and restore a more agreeable balance that could help as natural tick control.
AmeriCorps and Public Health Initiatives
The project addresses a number of social issues, including the burden of Lyme disease in a community as well as the need to engage under- and unemployed people in meaningful work which serves their local community and can teach them transferrable skills to take into employment. AmeriCorps is a federal program in the US where nonprofit community organizations work alongside public agencies to carry out projects involving local people in full or part time positions. Beginning in 1994, AmeriCorps now has over 80,000 members who work in areas of education, public health and safety, as well as environmental protection. This latest project arguably covers all such bases, helping raise awareness of Lyme disease and biodiversity, reducing the risk of exposure to ticks carrying bacteria like Borrelia burgdorferi, and decreasing the incidence (hopefully) of Lyme disease in the local population.
What is Japanese Barberry and Why Does it Matter?
Employing out-of-work locals and volunteers appears to have the added benefit of strengthening community ties and civic responsibility, with more people choosing to go into careers in public service after a stint in AmeriCorps. Perhaps a Lyme disease task force could be established across the US, under the umbrella of AmeriCorps in order to tackle invasive plant species and raise visibility of Lyme disease prevention efforts. Japanese barberry is considered an invasive plant species in at least twenty US states and the District of Columbia but remains on sale at many plant nurseries across the country. Once planted and established, Japanese barberry is able to spread across a variety of soil types, under variable conditions and reproduces quickly through seeds, rhizomes, and layering. It is fine in full sun, shade, and anything in-between and grows in thick blankets that cover over native wildflowers and tree saplings preventing them from getting established or being pollinated.
Controlling Invasive Plant Species
Japanese barberry has a 90% seed germination rate and birds eating the seeds will carry them off to deposit them in new places where the plant quickly roots and spreads. Previous attempts to develop sterile cultivars of invasive species like Japanese barberry may be ineffectual or even harmful as these plants may cross-pollinate with local native species and become even more effective at colonizing space.
How Japanese Barberry and Lyme Disease are Connected
The thickets of Japanese barberry tested by the CAES researchers were found to have an average of 120 Lyme disease-infected ticks per acre, compared to around 10 infected ticks per acre in those areas populated by native trees and plant species with no Japanese barberry present. This appears to be due, at least in part, to the moisture retention that occurs with the thick blanketing of the barberry, an environment particularly loved by ticks who do best at around 80% humidity. Ward and Williams noted that in sunny areas without the plant this humidity level only occurred for around an hour a day, whereas under Japanese barberry there was only an hour a day where levels dropped below 80% humidity. This allows for rampant feeding, foraging, and reproduction of the ticks, especially because white-footed mice, a favored tick host, also enjoy living under the barberry.
Killing Japanese Barberry to Decrease Lyme Disease
Japanese barberry, in addition to increasing the risk of contracting Lyme disease, also impacts soil quality and contributes to soil erosion which affects nearby water sources. To control Japanese barberry’s spread is difficult but the CAES researchers developed a two-stage plan: kill the plant above ground by cutting or burning with a propane torch, then treat the root regrowth with a chemical herbicide. In Oxford, the work already done to cut back and burn the Japanese barberry will be followed up in October by the application of herbicide to kill the weakened plant. Experts suggest that several rounds of this two-step program will be necessary for well-established areas of the invasive plant.
Restoring Biodiversity for Lyme Disease Control
Simply killing the plant is not enough, however, as the area needs to be planted with native flora to re-establish biodiversity and reduce the risk of other invasive species taking advantage of bereft soil. Landscapers need to be cognisant of local fauna, including deer, so as to set up animal fences and prevent plants being eaten and/or trampled before they become established.
In light of the recent revelations by the US Centers for Disease Control that rates of the infection are about ten times previously published figures, at 300,000 cases of Lyme disease a year in the US, taking steps to restore biodiversity, reduce tick numbers, and lessen the risk of exposure to Lyme disease bacteria by removing Japanese barberry seems increasingly wise.
Japanese Barberry Control Methods Reference Guide for Foresters and Professional Woodland Managers, Special Bulletin, February 2013, By Jeffrey S. Ward, Scott C. Williams, and Thomas E. Worthley.