Sorghum bicolor

Shattercane plant
Shattercane plant. Photo courtesy of Pethan. Licensed under CC BY-SA 3.0.
Shattercane is a rapidly growing annual grass that can grow up to 12 feet tall, known to significantly reduce yield if left unchecked. It is commonly associated with its perennial relative, johnsongrass. It was originally introduced to the U.S. as a forage crop.
Shattercane seeds remain viable in the soil for 2 to 3 years. At germination, its seedlings heavily resemble those of corn and johnsongrass. They are only differentiated by looking at whether or not the first leaf blade runs parallel to the ground. If so, it is more likely to be johnsongrass.
Shattercane seedling
Shattercane seedling. Photo courtesy of Bruce Ackley. Licensed under CC BY 3.0.
As the plant matures, it closely resembles grain sorghum and corn. In a cross-section, the stems are round and slightly compressed. It remains as a single stem, unbranched with hard internodes and the occasional purplish spot. Leaves are smooth and waxy with a fairly noticeable white midvein running the length of its blade, which has an overall rough edge. The sheaths of shattercane are pale green to reddish, ribbed, slightly hariy to hariless at the collar, and open. The leaf blades are overall longer than those of johnsongrass.
Shattercane plants growing in a field
Shattercane plants growin in a field. Photo courtesy of Howard F. Schwartz. Licensed under CC BY 3.0.
The flower clusters of shattercane bloom from May through October, emerging as compact and upright flowering branches. Sometimes they open up to a pyramidal shape that droops at the very top. The color of the flower clusters begin as pale or violet green, but as they mature, they become a dark-reddish color or purplish-brown. Each seedhead can produce up to 2,000 seeds. Shattercane's namesake comes from the way it sheds or "shatters" its many spikelets at the completion of maturity.
Shattercane plants in the flowering stage. Photo courtesy of Howard F. Schwartz.
Shattercane plants in the flowering stage. Photo courtesy of Howard F. Schwartz. Licensed under CC BY 3.0.
Shattercane tends to form very dense colonies wherever it becomes established, displacing any other plants growing in that area. Its success as a weed is owed to the ability to thrive in a wide variety of habitats. It has become a big contributer to yield loss in cornfields throughout the United States.
Fall and spring tillage are known to be effective in preventing or controlling shattercane. Rotation and cover crops are also a common way to provide healthy competition for shattercane weeds. Preventing the establishment of shattercane in cropfields is always less costly and time consuming than that of controlling the weeds once they are established. Be sure to buy clean seed, control fencerows and noncrop areas, avoid driving equipment through isolated weed patches, and thoroughly clean any machinery that has been worked in an infested area.
Glyphosate is known to be an effective postemergence herbicide. Other foliar treatments in corn include nicosulfuron alone or mixed with rimsulfuron and atrazine, primisulfuron alone or mixed with prosulfron, glufosinate, sethoxydim, and imazethapyr. EPTC is an effective preemergence herbicide in corn. In soybeans, the one of the best preemergence herbicides is clomazone. Some postemergence herbicides for soybeans include quizalofop, fluazifop alone or with fenoxaprop, glufosinate, sethoxydim, clethodim, and imazethapyr. Please contact your local weed specialist to learn what is most effective in your area and how to use it best. Always read and follow all label instructions.