There is a multi-year study going on now in Connecticut which looks at the relationship between Japanese barberry (Berberis thunbergii), white-footed mice and blacklegged ticks. Admittedly a strange combination.
Recently, results of the first two years of the study were released and they are a bit surprising. In essence, the study found the larger the number of Japanese barberry in an area, the higher the incidence of Lyme disease carrying ticks. Yikes! Yet another reason to rip these invasive plants out of your garden.
Here are a few highlights from the study:
– The study’s authors asked two basic questions. First, do higher populations of white-footed mice and blacklegged ticks protected by a dense under story of Japanese barberry have a higher incidence of Lyme disease? And second, if Japanese barberry are controlled, will the population of blacklegged ticks be reduced and therefore, the rate of Lyme disease infection in white-footed mice also be reduced?
- Japanese barberry was chosen, in part, because it is generally considered a deer-resistant shrub in most locations. For anyone who gardens in an area with deer, you know how fickle a deer’s taste buds can be but Japanese barberry is typically uneaten.
- The study looked at three test sites in Connecticut. The first site was located in area where the Japanese barberry was very dense. The second site included a thick grove of Japanese barberry that was cut to the ground and controlled during the study. The third site contained no Japanese barberry at all.
- Results of the first two years of the study have shown that feeding larval ticks and adult tick populations were highest in the high density barberry site. The highest incidence of Lyme disease carrying ticks was also found in the high density barberry areas.
- After cutting the Japanese barberry, the infection rate of Lyme disease in the white-footed mice remained the same the first year but was significantly reduced the second year , becoming equal to the areas that had no Japanese barberry growing.
- The study concluded that Japanese barberry infestations threaten humans by creating a favorable environment for ticks and mice. And high populations of mice and ticks leads to an increase in the incidence of Lyme disease.
All in all, the study gives gardeners yet another reason to stop buying and planting Japanese barberry. Unfortunately I was not able to find a free link to the full study but I do have a .pdf copy that I will be happy to share. If you’d like a copy of the study, just leave a comment and I’ll contact you directly.