DMI fungicides

There are approximately 20 enzymatic steps from lanosterol to cholesterol or ergosterol, and probably as many from 24-methylenedihydrolanosterol to ergosterol. 

The fungicides that inhibit fungal CYP51 are often called demethylase inhibitor (DMI) fungicides, but the group is chemically very diverse. A DMI 

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Other examples of DMI fungicides are the pyrimidinylcarbinols and piperazines (Figure 4.4). Fenarimol and nuarimol are minor products and the only members of the pyrimidinylcarbinols. Fenarimol is the most versatile being used in fruit against mildew and scab diseases. 

The principle action of the DMI fungicides is to inhibit the action of the cytochrome 450-dependent removal of the 14a-methyl group from 24-methylene dihydrolanosterol. The resulting accumulation of the substrate 24-methylene dihydrolanosterol, obtusifoliol and 14a-methyl-fecosterol, together with the consequent reduction in ergosterol synthesis, disrupts the normal functioning of cell membranes and was thought to be the basis of DMI activity. 

The biological activity of prochloraz has already been reported (4) and will only be summarised here. Although the compound has the same fundamental mode of action as other commercial DMI fungicides, It has a unique spectrum of activity and can be used on a number of crops. 

DMI Fungicides XX X For single product Alternation singly or in blocks Example Bananas... 

Table III. Transfer of C triadlmenol from barley to Eryslphe gramlnls f.sp. hordel strains differing in sensitivity to DMI fungicides...

Based on these findings the FRAC DMI Working Group recommends that repeated application of DMI fungicides alone for the control of cereal diseases in the same... 

The fungicides are very versatile in the contol of fungi that have become resistant to the demethylase inhibitor (DMI) fungicides described later. They have surprisingly low mammalian toxicity, but as with many other respiratory poisons, they show some toxicity to fish and other aquatic organisms. They may also be toxic to earthworms. In fungi they inhibit spore germination. The structures show the natural products strobilurin B and azoxystrobin, which has been marketed since 1996. 

Examples of DMI fungicides from each group 5.1.4.1 Azoles and triazoles... 

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