The lipid inhibitors include the aryloxyphenoxypropionate and cyclohexanedione herbicide families: These herbicides prevent the formation of fatty acids, components essential for the production of plant lipids. Lipids are vital to the integrity of cell membranes and to new plant growth. The lipid inhibitor herbicides inhibit a single key enzyme involved in fatty acid big-synthesis (Figure 1). Broad-leaf plants are tolerant to these herbicide families, but almost all perennial and annual grasses are susceptible. Injury symptoms are slow to develop (seven to 10 days) and appear first on new leaves emerging from the whorl of the grass plant. These herbicides are taken up by the foliage and move in the phloem to areas of new growth.
1. Cyclohexanediones
a. Use: Sethoxydim (Poast Plus) for soybean and alfalfa.
(Poast) for soybean, alfalfa, sugarbeet, flax, sunflower, lentil, pea and
potato.
Clethodim (Select) for soybean.
b. Injury Symptoms: Sugarbeet is not injured by cyclohex-anediones even at high rates.
c. Site of Action: Acetyl-CoA carboxylase enzyme.
2. Aryloxyphenoxypropionates
a. Use: Diclofop (Hoelon) for small grain.
Fluazifop (Fusilade 2000) for soybean.
Fenoxaprop (Whip, Option II) for soybean and
(Dakota, Tiller, Cheyenne) on small grain.
Quizalofop (Assure II) for soybean.
b. Injury Symptoms: Sugarbeet is not injured by aryl-oxyphenoxypropionates used alone but would be injured by mixtures with other herbicides such as in Dakota, Tiller or Cheyenne.
c. Site of Action: Acetyl-CoA carboxylase enzyme.