War on Weeds—weeds are everybody’s problem
Photo courtesy of Doug Doohan, Ohio State University/ OARDC, Bugwood.org
THE ISSUE: Large Crabgrass
Large crabgrass (Difitaria sanuinalis) is a summer annual grass native to Europe. It was introduced into the U.S. as a forage and is thought to be one of the first grasses used for grain production. While crabgrass is typically a bigger problem in the southern U.S. it can be a problem in warmer parts of Idaho. It is well suited to invade lawns and other turfgrasses especially when conditions are hot, dry and the soil is compacted.
Large crabgrass can grow up to 3 feet tall with leaves that are 1-6 inches long. Crabgrass has a hairy ligule (the collar shaped structure located between the blade and the sheath). When large crabgrass is young it may have small hairs, as it ages it may lose these hairs. Older plants take on a reddish-purple coloring as they mature. Crabgrass produces tillers (additional shoots), its stems can also root at notes as they grow along the ground. A single plant can produce up to 150,000 seeds in a single year.
Integrated Pest Management (IPM) Options:
• Prevention— Learn to identify this plant. Never transport unknown plant material. Plant clean seed!
• Mechanical— Hand pulling seedlings prior to seed production can be effective on small infestations.
• Cultural— Plant competitive beneficial vegetation. Use management practices that will benefit desirable vegetation. Ensure that turfgrass is being irrigated, mowed, fertilized, and aerated properly to strengthen beneficial plants. lift mower blades to at least 3 inches.
• Chemical—there are two ways to chemically control crabgrass, as the seeds are geminating (pre-emergent) or after seeds have germinated (post-emergent). Chemicals that can be used as a pre-emergent include: penimethalin, prodiamine, benefin, bensulide, and dithiopyr. Post-emergent options include: mesotrione, quiniclorac, topramezone, and dithiopyr. In general, herbicides are more effective on smaller plants. Always read and follow herbicide label directions!
Justin Hatch, University of Idaho Extension Agriculture Educator in Caribou County. 208-547-3205
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