356 Produce Degradation: Reaction Pathways and their Prevention
translocated both basipetally (downward) and acropetally whether applied to roots
or leaves (transport in phloem governed by osmotic pressure) [5,55].
A large group of systemic fungicides (sterol inhibitors) shares a common bio-
chemical target: the biosynthesis of ergosterol. Ergosterol is a major sterol in fungi
and it plays a vital role in membrane structure and function. The biosynthesis of
TABLE 11.5
Classification of Fungicides Based on Their Mode of Action and
Chemical Structure
Mode of Action Chemical Class Representatives
Nonsystemic Fungicides (mostly protectants)
Nonspecific thiol reactants,
inhibiting respiration
Alkylenebis
(dithiocarbamate)
Mancozeb, maneb, metiram, zineb
Phthalimide Captan, folpet
Sulphamide Dichlofluanid, tolylfluanid
Inorganic Copper hydroxide, sulfur
Inhibitors of enzymes containing
copper ions or sulfhydryl groups
Dimethyldithio-
carbamate
Ferbam, thiram, ziram
Inhibitors of spore germination
and growth of fungal mycelium
Dicarboximide Iprodione, procymidone, vinclozolin
Biphenyl o-phenylphenol, biphenyl
Inhibitors of protein or
phospholipid synthesis
Chlorophenyl Dicloran, quintozene, tecnazene,
tolclofos-methyl
Disruptor of glycolysis and energy
production
Chloronitrile Chlorothalonil
Cationic surfactants altering the
permeability of fungus cell wall
Guanidine Dodine, guazatine
Systemic Fungicides (protective, curative and eradication functions)
Demethylation inhibitors (DMIs),
i.e., ergosterol biosynthesis
inhibitors
Imidazole Imazalil, prochloraz, triflumizole
Pyrimidine Fenarimol, nuarimol
Triazole Fenbuconazole, flusilazole, myclobutanil,
propiconazole, tebuconazole,
triadimefon
Steroid reduction inhibitor, i.e.,
ergosterol biosynthesis inhibitors
Morpholine Fenpropimorph, tridemorph
Inhibitors of mitosis Benzimidazole Benomyl, carbendazim, thiabendazole,
thiophanate-methyl
Inhibitors of methionine
biosynthesis and fungal
hydrolytic enzyme secretion
Anilinopyrimidine Cyprodinil, mepanipyrim, pyrimethalin
Inhibitors of protein synthesis Phenylamide Benalaxyl, metalaxyl, mefenoxam
Inhibitors of mitochondrial
respiration by blocking electron
transfer
Strobilurin Azoxystrobin, kresoxim-methyl,
trifloxystrobin
Source:Tomlin, C.D.S., Ed., The Pesticide Manual, 12th ed., British Crop Protection Council, Surrey,
UK, 2000.