Pigment Inhibitors

Pigment inhibitors prevent plants from forming photosynthetic pig-ments. As a result, the affected plant parts become white to translu-cent. Clomazone (Command), a soil-applied herbicide, is the only member of the isoxazolidinone family in use at this time. Clomazone is taken up by plant roots and shoots and can move in the xylem to plant leaves. The newly developed foliage of many plant species is very susceptible to Clomazone and very small amounts can whiten new plant growth. Susceptible weeds will emerge as white plants before dying.

1. Isoxazolidinones

a. Use: Clomazone (Command) for soybean.

b. Injury Symptoms: All or portions of the true leaves will turn white (Photo 40). Sugarbeet is relatively tolerant of Clomazone residual in soil and generally plants with symptoms will live, turn green, and produce a nearly normal-size root at harvest.

c. Site of Action: Specific sites unknown.