War on Weeds — Weeds are Everybody’s Problem

Congongrass

Cogongrass (Imperate cylidrica) is a warm season perennial grass, native to parts of Africa and Asia. It was originally introduced into the U.S. in the early 1900’s as a forage and for soil stabilization. It is now considered one of the worst weeds in the world. It spreads by seed and aggressive rhizomes. Cogongrass contains oils that are flammable, causing it to burn very hot. It invades rights-of-ways and other disturbed sites.

Cogongrass can grow 2-5 feet tall and has yellowish green leaves. Leaves are flat, serrated and have a unique off-centered white mid-rib. It has distinctive fluffy white seed heads. Seed heads are 2-8 inches long and contain up to 3,000 seeds. White plumes on the seeds helps them to be transported easily on the wind. Because cogongrass is rhizomatous, it is often found in patches that expand in size.

Integrated Pest Management (IPM) options

• Prevention — Learn to identify this plant. Never transport unknown plant material. Always clean equipment and clothing after leaving invested areas. Plant clean seed.
• Mechanical — Tillage alone is not generally recommended as it will break up rhizomes and allow cogongrass to spread.
• Cultural — Burning infested areas in late summer and then applying a herbicide to regrowth can be an effective control option.
• Chemical — Glyphosate and Imazapyr are two non-selective herbicides that can effectively control cogongrass. Because these herbicides are non-selective, they will also kill beneficial vegetation. It may take multiple applications to completely control cogongrass. Always read and follow herbicide label directions.

Idaho is a wonderful place with awesome natural resources, landscapes, agriculture and recreational opportunities. Weeds threaten all the things that we love about Idaho. To detect, contain and control weeds in Idaho we have declared “War on Weeds.” These short articles are designed to give a brief description of each species, an explanation about why it’s a problem, insights into identification and Integrated Pest Management control options. — Justin Hatch

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• Congongrass, 5-31