VIII. Cell membrane disrupters (SOA 14, SOA 22)
The cell membrane disrupters include the following herbicide families:
- Diphenylether
- Imine
- N-phenylphthalimide
- Pyrimidinedione
- Triazolinone
- Bipyridylium
These herbicides are primarily postemergence-contact herbicides that are activated by exposure to sunlight to form oxygen compounds such as hydrogen peroxide. These oxygen compounds destroy plant tissue by rupturing plant cell membranes. Destruction of cell membranes results in a rapid browning (necrosis) of plant tissue. Herbicide injury symptoms can occur in one to two hours on a bright, sunny day. Because these are contact herbicides, they are excellent for burndown of existing foliage and postemergence control of annual weeds. Perennial weeds usually regrow because the herbicides do not move to underground root or shoot systems.
N-phenylphthalimide, pyrimidinedione and triazolinone herbicides are soil-applied and absorbed by root and shoots. Susceptible plants become necrotic and die shortly after emergence and exposure to light following soil application.
Herbicide use
- Acifluorfen (Ultra Blazer) for soybean.
- Lactofen (Cobra) for soybean.
- Fomesafen (Reflex, Flexstar) for soybean.
Injury symptoms
Affected leaves will exhibit desiccation where the herbicide contacts the plant (Photos 58, 59,60). Directed or indirect application (drift) generally will not kill sugarbeet, but the plants may be severely stunted, especially in high temperature and humidity environments. New growth will appear normal.
Fomesafen may carryover to sugarbeet, especially as soil pH increases above 6.5 or with cold and dry conditions that inhibit microbial activity. Injury from residues appears as stunting and mottled chlorosis and necrosis.
Site of action
Inhibition of photoporphyringen oxidase (PPO).
Herbicide use
Fluthiacet (Cadet) for soybean.
Injury symptoms
Same as diphenylether herbicides; see previous section. Carryover is unlikely.
Site of action
Inhibition of photoporphyringen oxidase (PPO).
Herbicide use
Flumioxazin (Valor/Chateau), premixes containing flumioxazin for alfalfa, corn, potato, soybean and sunflower.
Injury symptoms
Carryover can occur when flumioxazin is applied at high rates and when tillage is limited. Injury is most likely when precipitation increases herbicide availability in the soil solution and as the sugarbeet hypocotyl approaches or emerges through the soil surface (Photo 61).
Symptoms include necrotic lesions on sugarbeet cotyledons and hypocotyl, and often are more severe in poorly drained areas of the field. The hypocotyl can be girdled, resulting in sugarbeet plant death (Photo 62).
Site of action
Inhibition of photoporphyringen oxidase (PPO).
Herbicide use
Saflufenacil (Sharpen) for alfalfa, chickpea, corn, field pea, lentil and soybean; harvest aid/desiccant for small grains, dry bean, flax, field pea, soybean and sunflower.
Injury symptoms
Same as diphenylether herbicides. Carryover injury to sugarbeet is not expected due to the short-lived residual of this active ingredient.
Site of action
Inhibition of photoporphyringen oxidase (PPO).
Herbicide use
- Sulfentrazone (Spartan) for use in chickpea, dry bean, flax field pea, lentil, potato, soybean and sunflower. Premixes: Authority Assist, Authority Elite, Authority MTS or Spartan Elite.
- Carfentrazone (Aim) for barley, oat and wheat. Premixes: Spartan Charge for chickpea, dry bean, field pea, flax, lentil, soybean and sunflower.
Injury symptoms
Same as diphenylether herbicides (Photo 63). Sulfentrazone residue may remain in soil the following season(s).
Sulfentrazone solubility increases as soil pH increases above 6.5, as soil texture changes from fine to coarse, and as OM decreases. As sulfentrazone solubility increases, risk of crop injury increases.
Sugarbeet is ranked as a highly sensitive broadleaf crop.
Site of action
Inhibition of photoporphyringen oxidase (PPO).
Herbicide use
Paraquat (Gramoxone SL) for nonselective weed control preplant. Desiccation of potato vine and sunflower.
Injury symptoms
Drift on sugarbeet often will appear as spotting of leaf tissue (Photo 64). High amounts of drift or an accidental application may cause patches of brown tissue on leaves (Photo 65).
Spots from bipyridylium drift have been confused with foliar disease such as Cercospora or bacterial blight (Photo 48).
Generally, the pattern of injury in a field can be used to distinguish between disease and drift. If in doubt, samples should be taken to a diagnostic laboratory for disease identification.
Site of action
Diverts electrons from the photosystem I (PSI) complex of the photosynthetic electron transport chain.
CAUTION: Mention of a pesticide or use of a pesticide label is for educational purposes only. Always follow the pesticide label directions attached to the pesticide container you are using. Be sure that the area you wish to treat is listed on the label of the pesticide you intend to use. Remember, the label is the law.
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Reviewed in 2018