Friday, August 09, 2013

Mile-a-Minute


Mile-a-minute climbing up a tree © 2013 Beatriz Moisset
In my walks along some local trails, especially the Horsham power line right-of-way trail, I often see a weedy vine called mile-a-minute. The name is a humorous reference to its speedy growth. Exaggeration or not, it can enshroud entire trees and shrubs to the point of killing them. Wherever it goes, it changes the landscape. You can recognize it easily by its triangular leaves and its thin stems armed with insidious minuscule barbs that cling to your clothes or hands if you dare to come near, and by the thick mats of vegetation on the ground or climbing up trees.

It arrived from East Asia in the 1930s, accidentally introduced to York Pennsylvania along with horticultural stock. From there, it started an inexorable march across Pennsylvania and nearby states. With the help of birds that carry its seeds, it spreads to disturbed areas, such as power line clearings and roadsides. Now, I know why it is so abundant along the Horsham trail. Its seeds can also be carried by water, enabling it to spread along rivers. Since its arrival, it has spread to surrounding states and shows no signs of slowing down.
Notice the triangular leaves full of holes
© 2013 Beatriz Moisset

Like with many other invasives, the reason for its success is that it left behind the natural enemies that kept it in check in its native land. This is why I was surprised when I began to notice leaves full of holes. Who is eating this invasive plant? Did a local insect develop a taste for this unfamiliar food? Not so, it turns out that an ancient enemy of the vine, a small weevil, has been intentionally brought from East Asia.
Mile-a-minute weevil at the tip of the vine
© 2013 Beatriz Moisset

Before bringing this beetle from overseas, horticulturists needed to make sure that it would not start eating other plants, causing more damage than benefits. The Forest Service launched a program of testing the beetle, which they dubbed the mile-a-minute weevil of MAM weevil for short. In 2004, when researchers were confident enough of the results, they began introducing batches of this beetle to several sites in New Jersey. The results were encouraging; the beetle is reproducing well and it seems to have some impact on the plant. In recent years the beetle has been released in many other sites in ten states.
Mile-a-minute weevil (Rhinoncomimus latipes)
© 2013 Beatriz Moisset
Armed with this knowledge, I started my search for the mile-a-minute weevil in areas where I had seen leaf damage. It didn't take me long to find it. I was surprised at how small it is, less than one eighth of an inch, just a reddish grey dot. It chooses to eat only the tender leaves at the tip of each stem. Almost every plant I looked at had some weevils. In one case I found six of them in the same cluster of new leaves. They were busy mating and I was happy to photograph them. Despite all the holes in the leaves, the plants looked quite healthy. Perhaps, it would take a few more years for the mile-a-minute weevil to multiply in numbers high enough to have an impact on this weed. So, I congratulated the happy couples and let them go forth and multiply.
Busy beetles to the rescue
© 2013 Beatriz Moisset

1 comment:

Sharon McQueen said...

Just curious if there are any redeeming qualities to the vine. Like, edible for humans or good herbal properties. Even kudzu can be eaten and a starch type powder is made from the roots that can be used as a thickening agent in soups, etc. Also, the vines can be used for making nice baskets.