 |
| 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
|
