In Pennsylvania, the heaviest infestations of this pest occur in the south-central and southeastern portions of the state where it grows along roadsides, river and stream banks, utility rights-of-way, and on disturbed forest sites. On recently harvested forest sites, communities of mile-a-minute often become established and form dense canopies over establishing regeneration, resulting in tree seedling mortality.
Mile-a-minute is an annual plant that is easily recognized by its viny stems (up to 20 feet long) and light green, triangular leaves (1-2.5 inches across). Other identifying features include numerous sharp, downward curving spines on the stem, petiole, and main leaf veins; a saucer-shaped sheath that encircles the stem at the nodes; and round, iridescent blue fruit about 0.25 inches in diameter borne in terminal clusters from mid-July until frost. In southern Pennsylvania, seed germination begins in early to mid-March and continues through April. Mile-aminute establishes and grows best in moist, sunny locations with an abundance of plant litter such as leaves, duff, or brush on the soil. Slash and woody debris piles left at log landings are ideal growing sites for mile-a-minute.
Various means of seed dispersal are responsible for the spread of mile-a-minute. Along streams, water dispersal is no doubt the primary means of movement. On upland sites, birds, rodents, and man are most likely responsible for the spread of mile-a-minute. People aid in the spread of mile-a-minute by moving soil containing mile-a-minute seeds from one location to another. Examples of this are the shipment of potted nursery stock containing mile-a-minute seed or seedlings and the movement of heavy equipment laden with soil from one harvesting site to another.
Several effective means of controlling mile-a-minute exist. The simplest means is mechanical control, i.e., hand pulling, mowing, or cultivating. Hand pulling when wearing gloves is easy since it is a shallow, rooted plant. Once pulled, the plant will not resprout. For larger infestations where pulling or mowing is not feasible, chemical control can be used. Several herbicides labeled for forestry applications have proven effective in controlling mile-a-minute. These include the herbicides Arsenal (imazapyr), Oust (sulfometuron methyl), Roundup (glyphosate), and Velpar (hexazinone). Biocontrol, involving the use of diseases and insects, is currently being studied as another possible form of control. Whatever form of control is used, it is important to remove the plants before the fruits start to ripen in mid-July to prevent its spread and further contamination of the site.
Prepared by Larry H. McCormick, Professor of Forest Resources