Perennial Weed Control (Quackgrass, Field Bindweed, Canada Thistle, Johnsongrass, etc.)

clopyralid (Stinger)

See "Corn-Postemergence" in this section of this handbook.

Rate Apply 0.124 to 0.25 lb ae/A (0.33 to 0.66 pint/A of Stinger)

Time Any time after sweet corn emerges until it is no more than 18 inches tall.

Remarks To control Canada thistle, apply when most thistle plants have emerged and thistles are at least 6 to 8 inches wide or tall, but before bud stage. For best results on Canada thistle, use at least 0.5 pint/A product.

glyphosate (Roundup and several other trade names)

Rate 2.25 to 3.75 lb ae/A

Time Apply to weeds before crop emergence or post emergence in glyphosate tolerant corn.

Remarks Rate depends on species and growth stage as specified on label. Use highest rate on field bindweed. Treat perennial weeds when there is a maximum leaf surface and the weed is growing vigorously. Consult label for interval between application and tillage. Add water conditioning agents, such as AMS, prior to adding glyphosate if spray water has a low pH.

Caution Do not apply to weeds stressed by drought, weather, or maturity. Rain within 6 hours after applying may reduce effectiveness. Be sure to control weed escapes in following years. Do not use glyphosate in galvanized or mild steel tanks. Do not feed or forage treated vegetation within 8 weeks of application. Do not apply glyphosate with aerial equipment. Do not mix with other pesticides or herbicidal oils unless specified on label. For best results, spray coverage should be uniform and complete. If repeat treatments are needed, apply before crop emerges; the total of both treatments must not exceed 6 lb ae/A of glyphosate per crop. Glyphosate is tightly adsorbed or inactivated in the soil.

Site of action Group 9: inhibits EPSP synthase

Chemical family None generally accepted