NC State Extension Publications

Problem

Herbicide injury from lipid biosynthesis (Acetyl CoA carboxylase or ACCase) inhibitors including fenoxaprop-P, fluazifop-P and other aryloxyphenoxypropionates (FOPs) or cyclohexanedinones (DIMs) such as clethodim, sethoxydim and others.

Symptoms

  • ACCase inhibitors injure grasses, and only rarely affect certain sensitive broadleaf plants.
  • New growth cessation within a few days of treatment
  • Meristematic cells discolor and disintegrate just above the node
  • Leaves turn yellow, often wilt and then die
  • Leaf sheaths turn mushy and then brown
  • Seedlings lodge and eventually break off at the soil line
  • A few sensitive varieties of dicot plants exhibit variable symptoms, for example:
    • Tip die-back in sensitive varieties of ground cover junipers
    • Leaf burn (potentially from solvents) on certain azalea varieties
    • Red pigment loss in flower petals of sensitive tulip varieties

Plant Entry and Symptom Expression

Foliar applied and symplastically translocated throughout the plant. There is very little if any soil activity. Lipid biosynthesis inhibition starts with new growth within one week, spreads over entire plant including rhizomes, causing death in about 2 to 3 weeks. Low application rates may reduce flowering and seedhead production.

Similar Problems

  • Organic arsenical including DSMA and MSMA causing desiccation and death of annual and selected perennial grasses.
  • Quinclorac may produce similar symptoms in grasses, but will also cause synthetic auxin symptoms in dicots, whereas most dicots are unaffected by ACCase inhibitor herbicides
  • S-triazine rapid membrane distruction starting with older tissues.

Herbicide Mode of Action Category

WSSA - 1

HRAC - A

Authors

Prof. Emeritus, Cobleskill College
Horticultural Science
Professor of Weed Science, Extension Specialist & Department Extension Leader
Horticultural Science

Publication date: April 29, 2016

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