MAM, Persicaria perfoliata, is an invasive annual vine imported, probably by accident since I can't imagine why anyone would choose to plant it, from Asia. It's related to native tearthumb plants. MAM is a thin deciduous annual vine that has tiny barbs on its stem which stick into your skin if you're trying to pull it out or pass through it on a trail.
MAM has ocrea, triangular-shaped leaves, has inconspicuous flowers, and produces blue berries. In addition, it can grow up to six (6) inches in a day, hence its name "mile a minute". It grows over and covers native plants killing them since they can't photosynthesize under the leafy vine. Even though the plants are annuals, they are prolific seeders and seeds persist in the soil for about six years.
A few of the sites I visited are experimental. This means that in an attempt to combat the MAM, Asian weevils were carefully studied, raised and released on the properties in the hope that the weevils would do here what they do in Asia: The weevils eat the MAM; they use its stems to harbor larvae and keep the plant under control.
It's going to take a while for the weevils to do their jobs although on one site, it seems as though they're starting to be effective at reducing the MAM population. However, the MAM isn't waiting around to be eaten. It's growing quickly and spreading fast.
Some land managers are pulling the MAM even in areas where the weevils were released. This can be problematic to the scientists doing their experiments as the weevils burrow into the MAM's stems. So if you're pulling MAM, you could be destroying weevil larvae in the stems or later, in the ground where they spend a portion of their life cycle.
I understand the managers desire to pull the plants. MAM is a prolific grower. Mice, birds and deer eat the berries and spread the seeds in their excrement. There are even reports of insects moving seeds. Water, too, carries the seeds and berries downstream thereby spreading it further. Pulling the plants does work fairly effectively to keep it under control. However, manual pulling is time consuming and laborious.
Some people prefer to let the weevils do their job. This is an experiment and should be treated carefully. Let the scientists do the experiment to better learn how the weevils work and what the interplay is between the MAM, the environment, the weevils. Let the scientists learn what the dynamics are. Let nature do its work...or not. But altering the variables isn't helping to determine whether or not the weevils will work effectively in this country.
In the interim, however, MAM is growing, producing berries, seeding the soil, being spread by animals, birds, insects, and water. The whole thing is quite the conundrum.
Pull the MAM or let the weevils do their work? I hope those weevils eat fast.
