Produce Degradation Pathways and Prevention

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.