Agricultural Chemicals - Fundamentals of Industrial Chemistry: Pharmaceuticals, Polymers, and Business - page 217

as safeners for crops such as corn, grains, and rice. Safeners have been used
for decades. They increase the activity of detoxification enzymes [62].

O

N

Cl

O

Cl
Benoxacor

12.5 FUNGICIDES

Fungicides are used to prevent mold and mildew in crops and seeds. They
have been classified by the Fungicide Resistance Action Committee (FRAC)
based upon 46 different fungicide and bactericide modes of action. Two of the
major groups, based upon percent sales are the DMI fungicides in group G1
and the QoI fungicides in group C3 [63]. The DMI fungicides inhibit sterol
biosynthesis. Ergosterol is the predominant sterol and is biosynthesized in
several steps involving 11 enzymes from squalene. One of those steps involves
removal of a methyl group at the C 14 carbon of the steroid. The group G1
fungicides inhibit this demethylation step and hence are called demethylation
inhibitors (DMI) [64].

C14 demethylation

HO

Squalene Lanosterol

Several step s

HO

HO

Ergosterol

There are different chemical classes used but DMI fungicides with the tri-
azole ring structure dominate. Examples of DMI fungicides containing the
triazole ring include tebuconazole, difenoconazole, and epoxiconazole. The
carbon bearing the hydroxy group in tebuconazole is chiral; the herbicide is