Johnsongrass, also known as Sorghum halepense, is more than just an invasive weed; it's a become a global menace for soybean farmers. This aggressive weed battles soybean for crucial resources like nutrients, water, and sunlight, leading to diminished crop yield and quality. Moreover, johnsongrass acts as a host for various pests and diseases, amplifying the susceptibility of soybean crops to these threats.

Johnsongrass competes with soybean for essential resources, causing stunted growth and reduced yield. It can also physically impede the growth of soybean plants by overshadowing them and blocking sunlight. Additionally, johnsongrass can harbor various pests and diseases, increasing the vulnerability of soybean crops to these threats.

(Image Credit: Steve Dewey, Utah State University,


How to Identify Johnsongrass

Johnsongrass stands tall and robust, often towering over 6 feet. It boasts a thick, coarse stem and broad, lance-shaped leaves that can extend up to 2 feet. The plant flaunts large, purplish seed heads that are hard to miss.

Johnsongrass' extensive, creeping rhizome system is a significant indicator of its presence. These underground stems enable the plant to spread quickly and endure unfavorable conditions. The rhizomes, coupled with the plant's characteristic seed heads, are strong signs of a johnsongrass invasion.

Johnsongrass can be identified by its towering growth, broad leaves, and large seed heads. However, the most conclusive identification hinges on the plant's rhizome system. These creeping underground stems are white to cream-colored and end in sharp points.

(Image Credit: John D. Byrd, Mississippi State University,


Johnsongrass Geography

Johnsongrass is a versatile weed that can prosper in diverse environments. While it's commonly found in the southern United States, it has spread globally. It favors warm, temperate climates and is often spotted in disturbed areas like fields, roadsides, and ditches.

Timing of Johnsongrass Emergence

Johnsongrass typically emerges early in the growing season. However, thanks to its rhizomes, it survives year-round, posing a persistent problem for farmers.

How to Manage Johnsongrass in Soybeans

An integrated approach for controlling johnsongrass in soybeans is preferred; that includes using soil-applied herbicides, post-emergence herbicides, crop rotation, and tillage for the most effective control. Multiple post-emergence herbicide applications may be necessary to control regrowth of rhizome johnsongrass.



Pendimethalin 3.80 Value Pick can be applied pre-plant to provide moderate control of seedling johnsongrass, but post-emergence applications are required for season-long control.

Remember to always read and follow the product labels for proper application rates and safety precautions.

By understanding johnsongrass and its impact on soybeans, you can take informed steps to protect your crops and ensure a successful harvest.


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This content was generated with the assistance of Norm℠, FBN’s artificial intelligence (AI) Ag Advisor, based on a dataset of information containing general industry best practices and research. The AI model did not use specific external sources to generate this content. Our process involves using AI to aid human subject matter experts with the initial drafting and/or refinement of content.

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Every product that labels JOHNSONGRASS as a weed, pest, or disease the product can be applied against is shown below. Click any product for label and more information.
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