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IPM1007, Practical Weed Science for the Field Scout: Corn and Soybean

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Practical Weed Science for the Field Scout: Corn and Soybean

Seedling growth inhibitors

Trifluralin injury. Notice the purple color, rolled up leaves as if drought stressed, and short, thick lateral root system.Trifluralin injury. Notice the purple color, rolled up leaves as if drought stressed, and short, thick lateral root system. Trifluralin injury. Notice the purple color, rolled up leaves as if drought stressed, and short, thick lateral root system.
 

Short swollen stem caused by trifluralin.
Short swollen stem caused by pendimethalin.Short swollen stem caused by trifluralin, above, and pendimethalin, left.
 

Pendimethalin cannot be used in preplant incorporated applications in corn because of the potential for severe root injury. Planting corn too shallow and followed by preemergence pendimethalin can also cause root clubbing and injury.
Pendimethalin cannot be used in preplant incorporated applications in corn because of the potential for severe root injury. Planting corn too shallow and followed by preemergence pendimethalin can also cause root clubbing and injury.
Pendimethalin cannot be used in preplant incorporated applications in corn because of the potential for severe root injury. Planting corn too shallow and followed by preemergence pendimethalin can also cause root clubbing and injury.Pendimethalin cannot be used in preplant incorporated applications in corn because of the potential for severe root injury. Planting corn too shallow and followed by preemergence pendimethalin can also cause root clubbing and injury.
 

Dinitroanilines chemical group

Herbicides

  • Trifluralin (Treflan and others)
  • Pendimethalin (Prowl and others)

Mode of action and characteristics of activity

  • Mitotic disruptor
  • Inhibits cell division and inhibits lateral root formation through inhibition of tubulin protein involved with cell division
  • Annual grass and small-seeded broadleaf weed control
  • Soil activity
  • Little translocation
  • Intermediate to long soil persistence

General symptoms

  • Stunted plants that do not fully emerge from the soil and have short, thick lateral roots
  • Grass shoots are short and thick and may appear red or purple in color
  • They may also appear to be drought stressed. Broadleaf plants may have swollen hypocotyls (stem emerging from soil)
  • Following preemergence treatments, callus tissue may appear at the base of soybean stems
  • Inhibits main and lateral root growth, causes swollen root tips, swollen hypocotyls at ground line, and delayed emergence

Injury from acetanilides/chloroacetamides and oxyacetamides on corn appears as buggy whipping or improper leaf unfurling.
Injury from acetanilides/chloroacetamides and oxyacetamides on corn appears as buggy whipping or improper leaf unfurling. Injury from acetanilides/chloroacetamides and oxyacetamides on corn appears as buggy whipping or improper leaf unfurling.
Injury from acetanilides/chloroacetamides and oxyacetamides on corn appears as "buggy whipping" or improper leaf unfurling.

Injury from preemergence applications of chloroacetamide/acetanilide and oxyacetamide herbicides appears as heart-shaped leaves or irregular crinkling and cupping of leaves.
Injury from preemergence applications of chloroacetamide/acetanilide and oxyacetamide herbicides appears as heart-shaped leaves or irregular crinkling and cupping of leaves.Injury from preemergence applications of chloroacetamide/acetanilide and oxyacetamide herbicides appears as heart-shaped leaves or irregular crinkling and cupping of leaves.
 

Injury from postemergence applications of chloroacetamide/acetanilide and oxyacetamide herbicides also appears as irregular cupping and sometimes strapping of soybean leaves. Injury is more likely with late applications.
Injury from postemergence applications of chloroacetamide/acetanilide and oxyacetamide herbicides also appears as irregular cupping and sometimes strapping of soybean leaves. Injury is more likely with late applications.Injury from postemergence applications of chloroacetamide/acetanilide and oxyacetamide herbicides also appears as irregular cupping and sometimes strapping of soybean leaves. Injury is more likely with late applications.
 

Chloroacetamides, oxyacetamides chemical group

Herbicides

  • Alachlor (Intrro or Microtech — soybean, corn, grain sorghum)
  • Metolachlor (Dual II Magnum, others — soybean, corn, grain sorghum)
  • Dimethenamid (Outlook — soybean, corn, grain sorghum)
  • Acetochlor (Harness, Surpass, Topnotch — corn)
  • Flufenacet (Define — soybean, corn)

Mode of action and characteristics of activity

  • Seedling root and shoot inhibitor
  • Specific sites unknown, but inhibits very long chain fatty acids
  • Annual grass and small-seeded broadleaf weed control
  • Soil activity
  • Translocates upward in xylem
  • Short to medium soil persistence

General symptoms

  • Terminal tissue inhibition
  • In broadleaf plants, heart-shaped leaves due to midvein inhibition
  • Rough, crinkled leaves with some cupping possible for broadleaves, and grasses will show stunted or malformed shoot and may be onion-leafed
  • Stunting of shoots that result in abnormal seedlings that do not emerge from soil
  • Grasses may leaf out underground and leaves may not properly unfurl

 

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