Revised June 2007

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Contents

• Principles of weed identification
• Weed scouting and mapping procedures
• Economic thresholds for weeds
• Herbicide injury
• Factors contributing to herbicide injury

Weed identification

Herbicides

• Herbicide mode of action families
• Growth regulators
• Amino acid synthesis inhibitors
• Lipid synthesis inhibitors
• Seedling growth inhibitors
• Photosynthesis inhibitors
• Cell membrane disruptors
• Pigment inhibitors

Related pages

• G1886, Controlling Drift of Crop Protection Materials
• IPM1021, Vine Weeds of Missouri
• IPM1023, Missouri Weed Seeds

Other related Web sites

• MU Extension Plant Diagnostic Clinic
• WeedSOFT™ yield loss calculator

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Practical Weed Science for the Field Scout: Corn and Soybean

Summer annual broadleaf

Ragweed, common (Ambrosia artemisiifolia)

A common summer annual weed of agricultural crops, pastures and roadsides. Seedlings have round cotyledons that are often purple underneath. Young leaves are opposite; subsequent leaves become alternate with age, with a dense covering of hairs over the entire leaf surface. Leaves are egg shaped in outline but highly divided. Stems are erect, branched, and have long rough hairs. Flowers are green and inconspicuous and produced at the ends of branches. The fruit that encloses the seed is a woody achene with several projections that resemble a queen's crown.

IPM1007, revised June 2007