Pigment Inhibitors

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WSSA Group Numbers

13 and 27

Where Used

Cropland, mainly to control broadleaf plants though some grasses are also susceptible.

Common Active Ingredients

Group 13: clomazone; Group 27: mesotrione, tembotrione,  and topramezone

Effect On Plant

Pigment inhibitor herbicides cause chlorophyll to be destroyed. There  are various ways this can occur, including inhibition of certain pigment production. The absence of these pigments allows excessive light energy to destroy chlorophyll, which causes visible leaf bleaching. Plants are unable to photosynthesize due to a lack of pigments, and they may die after their energy reserves run out.

Injury Symptoms

Leaves turn white and may look bleached (Figure 22), and this symptom may be most severe near the leaf veins while interveinal areas may remain green (Figure 23). Purpling of leaf edges may also occur. Leaves that grow after application or exposure may look crinkled.