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Biology

Microstegium (also known as jewgrass) is a summer annual grass native to Asia. It was used as packing material for porcelain from China and this may have been how it was introduced into the U.S. It was first discovered in the United States in Tennessee in 1919. Microstegium has spread through much of the East, and is found throughout Virginia.

Microstegium occurs primarily in moist, shady areas and is very invasive, crowding out native herbaceous vegetation. It will grow in turf, in ornamentals beds, in woods, and other sites that are shaded. Microstegium can grow in full sun but will be under stress, especially during hot, dry weather. According to Jeffrey Derr, a weed scientist from Virginia Tech, microstegium germinates slightly in advance of large and smooth crabgrass. It flowers much later than crabgrass, and it propagates strictly by seed. Microstegium has been reported to produce seed in 5% of full sunlight. This plant will tolerate mowing.

This species has a prostrate to somewhat upright form with multiple branches. It roots at the nodes, and later in the growing season the stems are somewhat wiry. Leaves are about 3 to 5 inches long, half an inch wide, and tapered at both ends. Due to its somewhat similar growth form, microstegium can be considered “the crabgrass of shade.” Microstegium is a very invasive plant and will dominate in suitable habitats. It reaches about 2 to 3 feet tall in unmowed situations.

Control Strategies

Weed scientists at Virginia Tech have learned that the pre-emergent crabgrass herbicides commonly used in turf and/or ornamentals will control this weed. According to this line of research, all herbicides provided good to excellent preemergence control of microstegium at one month after treatment. Control ranged from fair to excellent at 2 months after application, depending upon herbicide. At three months, some chemicals do not provide acceptable control of microstegium. Repeat applications are needed to maintain control throughout the growing season.

The same researchers also investigated post-emergence control of microstegium. The post-emergence grass herbicides provided good to excellent control of this weed.

Based on this data, several control strategies have been developed. The control programs closely follow those used for crabgrass control, especially with pre-emergence treatments. Application of a pre-emergence crabgrass herbicide in March (prior to emergence) will control early-season germination of microstegium. Use of split/repeat applications of a pre-emergence herbicide can provide longer lasting control.

Cultural strategies used to improve the competitiveness of turf over crabgrass, such as higher mowing heights, Fall fertilization, and Fall seeding of thin turf, assist in microstegium management programs. Since microstegium grows well in considerable shade, it may be difficult to establish dense stands of turf, ornamentals, or other desirable vegetation to out-compete this weed.

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