Revised November 2009

Download a free PDF of this publication (13285KB). PDF help

Printer-friendly version of this page

Guidelines to reprint or copy

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

  • Price: $4.00
  • Availability: 719

Contents

Related publications

Use our feedback form for questions or comments about IPM1007.

Find publications

Search MU Extension publications.

ADA Accessibile AddThis Widget
MU Extension near you

Page: « First    ‹ Previous    Next ›    Last »


Practical Weed Science for the Field Scout: Corn and Soybean

Cell membrane disruptors

Paraquat injury symptoms on soybeans will also progress from water-soaked lesions soon after application to necrotic lesions with red rings several days after application.
Paraquat injury symptoms on soybeans will also progress from water-soaked lesions soon after application to necrotic lesions with red rings several days after application.Paraquat injury symptoms on soybeans will also progress from water-soaked lesions soon after application to necrotic lesions with red rings several days after application.
 

Within only a few hours of application, water-soaked lesions can be seen on corn that has been damaged with paraquat.Within only a few hours of application, water-soaked lesions can be seen on corn that has been damaged with paraquat. Within only a few hours of application, water-soaked lesions can be seen on corn that has been damaged with paraquat.
 

Paraquat injury on other plants such as pumpkin, snap beans and squash and is similar in appearance to injury that occurs on soybean plants.
Paraquat injury on other plants such as pumpkin, snap beans and squash and is similar in appearance to injury that occurs on soybean plants.Paraquat injury on other plants such as pumpkin, snap beans and squash and is similar in appearance to injury that occurs on soybean plants. Paraquat injury on other plants such as pumpkin, snap beans and squash and is similar in appearance to injury that occurs on soybean plants.
 

Paraquat drift symptoms on corn will progress as necrotic lesions that will eventually be surrounded by brown or red rings. Paraquat injury will be confined to the foliage that comes in direct contact with the herbicide.
Paraquat drift symptoms on corn will progress as necrotic lesions that will eventually be surrounded by brown or red rings. Paraquat injury will be confined to the foliage that comes in direct contact with the herbicide.
Paraquat drift symptoms on corn will progress as necrotic lesions that will eventually be surrounded by brown or red rings. Paraquat injury will be confined to the foliage that comes in direct contact with the herbicide. Paraquat drift symptoms on corn will progress as necrotic lesions that will eventually be surrounded by brown or red rings. Paraquat injury will be confined to the foliage that comes in direct contact with the herbicide.
 

Bipyridilium chemical group

Herbicides

  • Paraquat (Gramoxone Inteon)

Mode of action and characteristics of activity

  • Disrupts cell permeability (membranes) by producing free radicals, activated by sunlight
  • Nonselective weed control
  • Very little translocation
  • Foliar activity
  • Inactivated by soil

General symptoms

  • Activated by light and causes foliar burn at site of droplet deposition
  • Plant leaves will have a limp, water-soaked appearance, which is followed by necrosis of contacted tissue
  • Drift injury will appear as speckling on leaf tissue
  • Necrotic lesions will eventually have red rings around the perimeter

Acifluorfen injury will appear as speckling followed by chlorosis then necrosis of tissue contacted by the herbicide.
Acifluorfen injury will appear as speckling followed by chlorosis then necrosis of tissue contacted by the herbicide. Acifluorfen injury will appear as speckling followed by chlorosis then necrosis of tissue contacted by the herbicide. Acifluorfen injury will appear as speckling followed by chlorosis then necrosis of tissue contacted by the herbicide.
 

Fomesafen carryover on corn appears as a clearing of the midvein and veins. This is referred to as veinal chlorosis.
Fomesafen carryover on corn appears as a clearing of the midvein and veins. This is referred to as veinal chlorosis.Fomesafen carryover on corn appears as a clearing of the midvein and veins. This is referred to as veinal chlorosis.
 

Injury from fomesafen can also appear as speckling, chlorosis and necrosis but more often causes leaf crinkling and distortion. New growth is not affected.
Injury from fomesafen can also appear as speckling, chlorosis and necrosis but more often causes leaf crinkling and distortion. New growth is not affected. Injury from fomesafen can also appear as speckling, chlorosis and necrosis but more often causes leaf crinkling and distortion. New growth is not affected.
 

Flumiclorac causes crinkling of leaves that were expanding when treated. Flumiclorac causes crinkling of leaves that were expanding when treated.
 

Flumiclorac injury on corn.Flumiclorac injury on corn.
 

Injury from flumioxazin drift on corn will appear as necrotic lesions and is often confused with paraquat.Injury from flumioxazin drift on corn will appear as necrotic lesions and is often confused with paraquat.
 

N-phenylphthalimides, diphenyl ether and pyrimidinediones chemical group

Herbicides

  • Acifluorfen (Ultra Blazer — soybean)
  • Lactofen (Cobra/Phoenix — soybean)
  • Fomesafen (Reflex/Flexstar — soybean)
  • Flumiclorac (Resource — corn and soybean)
  • Flumioxazin (Valor)
  • Saflufenacil (Sharpen — corn, grain sorghum and soybean; Integrity – corn, grain sorghum; Optill — soybean)
  • Fluthiacet (Cadet — corn and soybean)

Mode of action and characteristics of activity

  • Inhibition of protoporphyrinogen oxidase (PPO).
  • Foliarly applied, often referred to as contact herbicides
  • Little translocation in plants
  • Fomesafen also has soil activity

General symptoms

  • Plant leaves will yellow and then turn chlorotic, then necrotic
  • Reddish brown spotting on the leaf surface may appear shortly after the herbicide is applied
  • Plants that do not die may be stunted for a week or more
  • COC and other additives, as well as extremely cool or warm temperatures, may increase plant injury

Injury from carfentrazone on soybeans will appear as speckling, chlorosis and necrosis of contacted foliage. Note the absence of red rings surrounding the necrotic lesions as with paraquat.
Injury from carfentrazone on soybeans will appear as speckling, chlorosis and necrosis of contacted foliage. Note the absence of red rings surrounding the necrotic lesions as with paraquat.Injury from carfentrazone on soybeans will appear as speckling, chlorosis and necrosis of contacted foliage. Note the absence of red rings surrounding the necrotic lesions as with paraquat.
 

Carfentrazone injury on corn. Carfentrazone injury on corn.
 

Sulfentrazone injury on soybeans. Note the small leaflets, bent cotyledons and purple spots from sulfentrazone Sulfentrazone injury on soybeans. Note the small leaflets, bent cotyledons and purple spots from sulfentrazone "splash"in wet conditions.
 

Sulfentrazone-damaged soybean hypocotyls when cold, wet conditions occurred at emergence. Sulfentrazone-damaged soybean hypocotyls when cold, wet conditions occurred at emergence.
 

Injury from sulfentrazone drift on corn will also appear as necrotic lesions and is often confused with paraquat damage. Injury from sulfentrazone drift on corn will also appear as necrotic lesions and is often confused with paraquat damage.
 

Severe carfentrazone injury on corn as a result of rain washing the herbicide into the whorl. Severe carfentrazone injury on corn as a result of rain washing the herbicide into the whorl.
 

Aryl triazolinones chemical group

Herbicides

  • Sulfentrazone (Spartan — soybean and tobacco)
  • Carfentrazone (Aim — corn, soybean, wheat)

Mode of action and characteristics of activity

  • Inhibition of protoporphryinogen oxidase
  • Control of annual broadleaf weeds
  • Very little translocation
  • Soil and foliar activity
  • Short to intermediate soil persistence

General symptoms

  • Necrosis of leaf tissue
  • Plant leaves will yellow and then turn brown and die
  • Reddish brown spotting on the leaf surface may appear shortly after the herbicide is applied
  • Plants that do not die may be stunted for a week or more
  • Sensitive soybean varieties and extremely cool temperatures or wet soils may increase plant injury appearing as necrosis on the cotyledons and hypocotyl

 

Page: « First    ‹ Previous    Next ›    Last »


IPM1007 Practical Weed Science for the Field Scout: Corn and Soybean | Page 3 | University of Missouri Extension