Nature of New York: A Problem that Grows a Mile-a-Minute

Forest ecosystems from North Carolina to northern New England and west to Ohio are under siege from a knotty invasive vine that darts from the ground to the canopy at lightning speed. Mile-a-minute (Persicaria perfoliata), a native to China and Japan, can grow up to 30 feet in a single year and produces hundreds of seeds that have the capability to survive in the soil for up to 7 years. The fact that the seeds resemble plump blueberries makes them a tempting treat to wildlife. Deer and birds are efficient dispersers. Vines readily climb trees and other vegetation to form dense clumps that easily smother native species. This tyrannical engulfment has garnered the plant the name “Kudzu of the North.”

Just above New York City in the Hudson Valley, numerous state parks have seen native biodiversity nose-dive since the arrival of the plant here about a decade ago. The only thing that has appeared to increase is the number of invasive species that now call these city retreats home. It’s a serious issue that the Mile-a-Minute Project of the Hudson Valley of recent years has been attempting to mitigate. After finding hand-pulls hopelessly ineffective, in 2009 the staff turned to looking into using a newly tested biocontrol agent that was deemed safe by the University of Delaware. By releasing thousands of tiny weevils (Rhinoncomimus latipes), no bigger than the size of a pin head at the infestations, it was hoped these insects would significantly diminish the plant’s fecundity. R. latipes shares the vine’s native range in Asia and feeds exclusively on the plant, making it a prime biocontrol agent.

Once a year since 2009, the Mile-a-Minute Project has done releases on parkland with severe infestations. Around 15,000 weevils have been released at 9 sites since the program’s inception. Each location is monitored once a month from spring to autumn. Inundating the sites only once with large quantities of weevils has proven to be the most effective, over smaller, continual releases.

Apart from the weevils slowing the spread of the vine to new locales through a reduction in seed production, the biocontrol sites themselves generally show a 10% decrease in mile-a-minute the year following the release. Progress is slow, but steady.

The advantages of biocontrol over manual removal are significant: the weevils are self-perpetuating; they can travel a distance of 10-15 miles a year on their own; and can reach areas inaccessible to human eradicators. Additionally, these insects are cheap to obtain and save large quantities of time that would ordinarily have to be devoted to pulling the plants or by spraying them with herbicide.

When new regional infestations are investigated normally around 75% are found to contain hungry R. latipes munching on the plants. With the range of invasives rapidly expanding and new species getting introduced to the U.S. every year, biocontrol is quickly becoming the optimal measure to deal with these invaders.

Nature of New York

Saturday, January 11, 2014

A Problem that Grows a Mile-a-Minute

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