(22) Owens, Robert G,, and Helen M, Novotny, Mecha- 
nism of action of the fungicide dichlone (2,3- 
dichloro-1,4-naphthoquinone), Contrib, Boyce 
Thompson Inst, 19: 463-482, 1958, 
Owens, Robert G,, and Joseph H, Rubinstein, 
Chemistry of the fungicidal action of tetra- 
methylthiuram disulfide (thiram) and ferbam, 
Contrib, Boyce Thompson Inst, 22: 241-257, 
1964, 
Rader, Wm, E., C. M, Monroe, and R, R, Whet- 
stone, Tetrahydropyrimidine derivatives as 
potential foliage fungicides, Science 115: 124- 
125,,.19525 
Rich, Saul, Fungicidal chemistry. p. 553-602, 
In Horsfall, J, G., and A, E, Dimond, editors, 
Plant Pathology, v.2,715pp, Academic Press, 
New York, 1960, 
Rich, Saul, and James G, Horsfall, The relation 
between fungitoxicity, permeation, and lipid 
solubility, Phytopathology 42: 457-460, 1952, 
Fungitoxicity of ethylenethiourea deriva- 
tives, Science 120: 122-123, 1954, 
Ross, R, G,, and R, A, Ludwig, A comparative 
study of fungitoxicity and phytotoxicity in an 
homologous series of N-n-alkylethylenethi- 
oureas, Canad, Jour, Bot, 35: 65-95, 1957, 
(23) 
(24) 
(25) 
(26) 
(27) 
(28) 
(29) Sexton, W, A, Chemical constitution and biologi- 
cal activity, 424 pp. E, and F,N, Spon Ltd,, 
London, 1953, 
Sisler, Hugh D,, and Carroll E, Cox, Physiology 
of fungitoxicity, p. 507-552, In Horsfall, J, G., 
and A, E, Dimond, editors, Plant Pathology. 
v. 2, 715 pp. Academic Press, New York, 
1960, 
Stakman, E,C,,andJ. George Harrar, Principles 
of plant pathology, 581 pp, Ronald Press Co,, 
New York, 1957, 
Turner, N, Joe, L, E, Limpel, R, D. Battershell, 
H, Bluestone, and D, Lamont, A new foliage 
protectant fungicide, tetrachloroisophthalo- 
nitrile, Contrib, Boyce Thompson Inst, 22: 
303-310, 1964, 
Tweedy, B, A mechanism for the reduction of 
elemental sulfur by Monoliniafructicola, (Per=- 
sonal communication re mss, in preparation for 
publication in Contrib, Boyce Thompson Inst,) 
Wellman, R, H,, andS, E, A, McCallan, Glyoxali- 
dine derivatives as foliagefungicides, Contrib, 
Boyce Thompson Inst, 14: 151-160, 1946, 
Zentmyer, George A, Inhibition of metal catalysis 
as a fungistatic mechanism, Science 100: 294- 
295, 1944, 
(30) 
(31) 
(32) 
(33) 
(34) 
(35) 
THE FUTURE ROLE OF CHEMICALS FOR CONTROLLING 
PLANT NEMATODES 
J. M. Good and Julius Feldmesser, Nematologists, Crops Research Division, Agricultural 
Research Service, U.S. Department of Agriculture, Beltsville, Md. 
Plant-parasitic nematodes have been re- 
sponsible from the very beginning of agricul- 
ture for devastating losses to man's food and 
fiber crops. However, it was not until the 
mid-19th century that man was able to recog- 
nize these pests that for so many years had 
remained hidden in the soil and concealed 
within plant tissues. Since the first discovery 
of root knot on cucumbers in 1855, scientists 
throughout the world have made remarkable 
advances in describing hundreds of species of 
plant-parasitic nematodes and in defining their 
destructive role in modern agriculture. 
Nematodes are recognized as important pests 
of crops throughout the world. Our growing 
knowledge proves nematodes responsible for 
even greater losses than were first attributed 
to them by scientists. 
Without the use of modern nematocides 
and nematode-resistant crop varieties, losses 
92 
caused by nematodes would probably exceed 
10 percent of our annual crop production, and 
under some conditions highly susceptible crops 
would be virtually destroyed. Several types 
of nematodes are responsible for low soil 
productivity through their many direct and 
indirect activities in soil and within plant 
tissues. Their activity is often responsible for 
an increased incidence of plant diseases caused 
by pathogenic bacteria, fungi, and viruses. 
By impairing root systems, nematodes are 
also responsible for inefficient use of both 
major and trace elements. The incipient dam- 
age to plant roots caused by nematodes fre- 
quently necessitates costly application of 
supplemental irrigation and side dressings 
of fertilizer nutrients to compensate for the 
disfunctional, mutilated roots of infected plants, 
Complete knowledge of the role of nematodes 
in reducing soil productivity will, in heavily 
