NC State Extension Publications

Problem

Herbicide injury caused from protoporphyrinogen oxidase (PPO, PPG or protox) inhibitors including acifluorfen, flumioxazin, oxyfluorfen, fomesafen, sulfentrazone, oxadiazon, and others.

Symptoms

  • Interveinal chlorosis, bronzing, desiccation and then necrosis.
  • Foliar necrosis – spots, margins or general necrosis depending on the amount of spray exposure.
  • Petiole and tender stem necrosis.
  • Fruit lesions and necrosis.

Less commonly:

  • Leaf mid-vein reddening followed by necrosis.
  • Dark red leaf spots followed by necrotic leaf spots.
Flumioxazin spray drift on knockout rose one week after treatmen

Flumioxazin spray drift on knockout rose one week after treatment.

J. Neal  CC BY-NC-SA - 4.0

Darkening and necrosis of mid-veins in young knockout rose.

Darkening and necrosis of mid-veins in young knockout rose foliage, from root uptake of flumioxazin. Two weeks after treatment.

J. Neal  CC BY-NC-SA - 4.0

Flumioxazin spray drift on evergreen holly.

Flumioxazin spray drift on evergreen holly two weeks after treatment.

J. Neal  CC BY-NC-SA - 4.0

Necrosis of young tomato fruit from flumioxazin spray drift.

Necrosis of young tomato fruit from flumioxazin spray drift, three days after treatment.

B. Lassiter  CC BY-NC-SA - 4.0

Necrosis of tomato foliage and stems from flumioxazin spray drif

Necrosis of tomato foliage and stems from flumioxazin spray drift; three days after treatment.

B. Lassiter  CC BY-NC-SA - 4.0

Spotting and necrosis on grape leaves from flumioxazin spray dri

Spotting and necrosis on grape leaves from flumioxazin spray drift, three days after treatment.

B. Lassiter  CC BY-NC-SA - 4.0

Spotting and necrosis on strawberry leaves from flumioxazin.

Spotting and necrosis on strawberry leaves from flumioxazin spray drift, three days after treatment.

B. Lassiter  CC BY-NC-SA - 4.0

Fomesafen POST on strawberry one week after treatment.

Fomesafen applied postemergence over the top of strawberry one week after treatment.

K. Jennings  CC BY-NC-SA - 4.0

Plant Entry and Symptom Expression

PPO inhibitors can be applied pre or postemergence leading to foliar absorption in seedlings and some upward translocation. Light is needed to activate assimilated PPO inhibitors causing rapid cell membrane destruction on young seedling leaves, petioles and stems shortly after emergence. Spray drift to foliage results in rapid necrosis of tender tissues. More mature leaves and stems may not express symptoms. Various PPO herbicides display like symptomologies but may differ due to application timing and differential sensitivity in crops and weeds.

Similar Problems

PPO inhibitor injury may be confused with symptoms from:

  • Cell membrane disruptors such as paraquat, diquat, herbicidal oils and fatty acids.
  • Glufosinate.
  • Classical PS II, as-triazine such as metribuzin.
  • Rapid action PS II, benzothiadiazole such as bentazon.
  • Desiccation, salt injury, frost damage.

Herbicide Mode of Action Category

WSSA – 14
HRAC – E

Authors:

Professor Emeritus
Cobleskill Univ.
Professor of Weed Science, Extension Specialist & Department Extension Leader
Horticultural Science
Assistant Professor
Horticultural Science
Extension Associate, Horticulture
Horticultural Science

Publication date: Dec. 11, 2015

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