Produce Degradation Pathways and Prevention

Role of Pesticides in Produce Production, Preservation, Quality, and Safety 363

into the cell wall glucans. Naptalam and diflufenzopyr interfere with cell growth
and development by affecting indolyl-3-acetic acid (IAA or auxin) transport. Auxin
is a natural plant growth regulator that promotes cell elongation in plants.
The mode of action of many other soil-applied, preemergence herbicides consists
of direct or indirect inhibition of photosynthesis of emerging weed seedlings [1,5].

TABLE 11.8
Classification of Soil-Applied Herbicides

Mode of Action = Inhibition of: Chemical Class Representatives

Cell division:
(microtubule assembly)

Alkanamide Diphenamid, napropamide

Benzamide Propyzamide (pronamide), tebutam

(butam)

Benzenedicarboxylic

acid

DCPA (chlorthal-dimethyl)

Carbamate Chlorpropham, propham

Chloroacetamide Acetochlor, alachlor, dimethenamid,

metazachlor, S-metolachlor, propachlor

Dinitroaniline Benefin, ethalfluralin, oryzalin,

pendimethalin, trifluralin

Pyridine Dithiopyr, thiazopyr

Cell growth and development:
Lipid synthesis
(not acetyl CoA carboxylase)

Thiocarbamate Butylate, cycloate, EPTC, molinate,
pebulate, thiobencarb, tri-allate, vernolate
Phosphorodithioate Bensulide
Cellulose biosynthesis Benzamide Isoxaben
Benzonitrile Chlorthiamid, dichlobenil
Indolylacetic acid (auxin)
transport

Phthalamate Naptalam

Semi-carbazone Diflufenzopyr

Photosynthesis:
Photosynthetic electron transport
(Hill reaction)

Triazine and

triazinone

Atrazine, cyanazine, metribuzin, simazine

Uracil Bromacil, lenacil, terbacil
Urea Chlorotoluron, diuron, isoproturon, linuron
Protoporphyrinogen oxidase
(blocking chlorophyll synthesis
and leading to membrane lipid
destruction)

Diphenyl ether Acifluorfen, bifenox, fomesafen,
oxyfluorfen
Oxadiazole Oxadiargyl, oxadiazon
Triazolinone Amicarbazone, sulfentrazone
Carotenoid biosynthesis
(leading to destruction of
chlorophyll and membrane
lipids)

Isoxazolidinone Clomazone

Pyridazinone Norflurazon

Sources: Cremlyn, R.J., Agrochemicals: Preparation and Mode of Action, John Wiley & Sons LTD.,
Chichester, 1991 and Tomlin, C.D.S., Ed. The Pesticide Manual, 12th ed., British Crop Protection Council,
Surrey, UK, 2000.