This document summarizes information on four fungicides: Dithianon, Chlorothalonil, Etridiazole, and Phthalide. It provides the chemical name and structure, production method, mode of action, and example uses for each fungicide. Trade names are also listed for some of the fungicides. The fungicides have a broad spectrum of activity against various plant diseases and are used on crops like fruits, vegetables, coffee, and turf.

1. 14 Fungicides, Agricultural
local systemic activity. It is used mainly for con-
trol of apple scab but also for fruit rot and leaf
spot diseases of deciduous fruit and nuts.
Trade Names. Cyprex, Venturol, Melprex
(Cyanamid, Rhˆone-Poulenc); Dodene (Sipcam).
Dithianon [3347-22-6], 5,10-dihydro-5,10-
dioxonaphtho-[2,3-b]-1,4-dithiin-2,3-dicarbo-
nitrile, C14H4N2O2S2, Mr 296.3, mp 225 ◦
C,
vapor pressure 66 µPa at 25 ◦
C, consists of
brown crystals which are practically insolu-
ble in water and only slightly soluble in organic
solvents [9, p. 225], [13, p. 105].
Dithianon is produced by reaction of hy-
drogen cyanide with carbon disulfide in di-
methylformamide to yield dimercaptomaleic
acid dinitrile; this intermediate is then treated
with 2,3-dichloronaphthoquinone [40].
Dithianon (announced in 1963) is a protective
contactfungicidewithabroadspectrumofactiv-
ity against, for example, leaf and fruit spot dis-
eases, downy mildew, late blight, anthracnose,
and rust. It is relatively expensive and is used on
crops (e.g., deciduous fruit trees and coffee) only
when it produces significant benefits that are not
obtained with cheaper contact fungicides such as
dithiocarbamates.
Trade Names. Actuan, Delen (Cyanamid); Clus-
ter (Barclay).
Chlorothalonil [1897-45-6], tetra-
chloroisophthalonitrile, C8Cl4N2, Mr 265.9, mp
250 –251 ◦
C, bp 350 ◦
C, vapor pressure 1.3 Pa
at 40 ◦
C, consists of colorless crystals which
are practically insoluble in water but slightly
soluble in organic solvents such as acetone, cy-
clohexanone, and xylene [9, p. 120], [13, p. 91],
[14, p. 163].
Chlorothalonil is produced by reaction of
tetrachloroisophthalyl chloride with ammonia to
give the diamide which, on treatment with phos-
phorus oxychloride, yields the dinitrile [41].
Chlorothalonil (announced in 1964) has a
broad spectrum of activity and is used as a pre-
ventative foliar fungicide on a wide range of
crops including vegetables, turf, top fruit, cof-
fee, groundnuts, and cereals. It is relatively ex-
pensive and is usually used on more valuable
cultures.
Trade Names. Bravo (ISK Biosciences); Da-
conil (SDS Biotech, Zeneca, ISK Biosciences).
Etridiazole [2593-15-9], 5-ethoxy-3-tri-
chloromethyl-1,2,4-thiadiazole,C5H5Cl3N2OS,
Mr 247.5, mp 20 ◦
C, bp 95 ◦
C at 0.13 kPa, vapor
pressure 13 mPa at room temperature, is a yel-
low liquid with a persistent odor; it is practically
insoluble in water but soluble in many organic
solvents [9, p. 252], [14, p. 219], [15, p. 397].
Etridiazole is produced by reaction of
trichloroacetamidine hydrochloride with
trichloromethanesulfenyl chloride and then with
sodium hydroxide in ethanol [42].
Etridiazole (announced in 1969) is a soil
fungicide with preventative and curative prop-
erties. It is effective against Phytophthora and
Pythium spp. and is used on turf, ornamentals,
vegetables, avocados, and other crops. It can be
applied to the soil surface or mixed with the soil
prior to planting.
Trade Name. Terrazole (Uniroyal).
Phthalide [27355-22-2], 4,5,6,7-tetra-
chlorophthalide, C8H2Cl4O2, Mr 271.9, mp
209 – 210 ◦
C, consists of colorless crystals
which are practically insoluble in water and only
slightly soluble in organic solvents [9, p. 517],
[14, p. 197].
Phthalide is produced by treatment of 1,2-
bis(dichloromethyl)-3,4,5,6-tetrachloroben-
zene with 75 % sulfuric acid [43].