Japanese stilt grass and Voles

Japanese stilt grass

One of the most common invasive plants in the Eastern U.S., Japanese stiltgrass (Microstegium vimineum), is easily mistaken as a pleasing, green grass ground cover. Its bright-green, lance-shaped leaves can be recognized by their silvery center stripe with hairs down the middle of the leaf.

Japanese stiltgrass

Photo from Mike Kay

Although an annual, stiltgrass reproduces quickly through prolific seed production following its late summer, early fall bloom in mid to late September. It is best mowed for control while in bloom about late September, before the seed has developed. Since stiltgrass seeds remain viable in the soil for five to seven years, annual control for many years is required to remove it.

It thrives in a variety of light and soil conditions, taking hold in disturbed areas, including heavily deer-browsed forest floors in Frederick County. However, deer and other grazing animals are reluctant to eat it. When it takes hold in the understory of our forests and open areas, it out-completes the native plants and reduces the habitat preferred by native birds and animals. Also, it can diminish the fertility of soils by secreting “allopathic” chemicals that kill beneficial soil microorganisms.

Many believe that stiltgrass has become one of the worst invasive plants found in our region. This grim reality may change now that a naturally occurring fungus known as Bipolaris has been shown to kill the stiltgrass. The dieback of stilt- grass was first observed in Calhoun County, W.Va, in 2008, and in 2009 other outbreaks were observed in other sections of West Virginia, Maryland, and Indiana.

Researchers at Indiana University have been studying this development and a recent article appeared in the Journal of Plant Disease which details their preliminary observations. So far researchers do not know how the disease became established, how it spreads, or whether or not it will affect other plants. The disease first shows up in early June when dark lesions appear on the stiltgrass leaf; a few weeks later the plants turn brown, dry up and perish. This disease offers some hope that natural controls will reduce the impact of this aggressive invasive plant.

Many of our worst invasive species were brought to our country from foreign lands where they evolved in harmony with their local surroundings. Japanese stiltgrass is thought to have come to the U.S. as packing material from Asia in the early 1900s. Once these species were introduced to our area where, in most cases, no natural predators or controls were present, their populations grew out of control. In time, various factors can exert environmental resistance on these populations to help maintain the balance that is necessary in an ecosystem. Hopefully this will be the case with the stiltgrass.

Voles

Voles look a lot like mice, moles, shrews and other small rodents, with their mouse-like size and coloring. However, compared to mice, voles have sharper teeth, a less pointed head and smaller ears. They feed more than other small rodents on the bark and roots of woody plants.

In Frederick County, the common meadow vole (Microtus pennsylvanicus) is often called a field mouse. Voles find habitat in heavy plant matter like long grass and in small burrows. Voles are prolific at reproducing and can multiply several times during a year. They are naturally controlled by predators such as hawks, owls, foxes, snakes, coyotes, and cats, but they can decimate plantings when conditions provide a favorable habitat. Voles ring the bark of small trees and undermine and eat succulent root systems, with damage often not apparent until many plants have been killed. In winter, under cover of snow, their damage is even less noticed. Pesticide controls and vole habitat reduction by mowing at least twice a year (June and September) reduces populations.

Nature Notes for 10/6/2013