and on the precise manner in which various 
types of nematocides kill nematodes, We must 
know whether these materials are adsorbed 
on or leached from soil, degraded by micro- 
biological processes, or absorbed and trans- 
located by plants, In addition, realistic 
research programs must be continued to 
insure that food and fibers are free of harm- 
ful nematocide residues, unpalatable flavors, 
or poor quality. 
There is increasing evidence that when 
nematode damage to crop roots is eliminated, 
the amount of fertilizer applied to many crops 
can be reduced, and possible adjustments of 
the ratio of N, P, and K in fertilizer may be 
required, Also, trace element deficiencies in 
plants can be at least partially corrected by 
controlling nematodes, because a sufficient 
amount of trace elements may be mineralized 
in most soils to support normal plant growth, 
provided root systems are not debilitated by 
nematodes, Therefore, it is not unreasonable 
to think that fertilizer recommendations 
eventually may have to be reevaluated in 
order to satisfy the nutritional needs of plants 
with nonnematized root systems, In addition, 
several exploratory-type investigations have 
established that modern irrigation practices 
may increase nematode infestations and that 
plants with nematode-damaged roots have 
different water-utilization relations than 
healthy plants, Such findings indicate that 
additional research should be undertaken to 
evaluate the effect of nematocides on the use 
of irrigation, fertilizers, seeding rates, and 
other management practices after the soil has 
been freed of nematodes, 
Increased mechanization and interest of 
growers in reducing the operational costs of 
applying pesticides may require a single, 
combined application of agricultural chemi- 
cals, A few experiments have indicated that 
multiple pest control is possible either before, 
at the time of, or after fertilization and 
seeding, However, there is a need for addi- 
tional evaluation of integrated soil pesticide 
programs, in which nematocides, fungicides, 
herbicides, and insecticides are applied to- 
gether, or within short intervals, because not 
all pesticides may be compatible when used 
together on some crops, Combinations of 
pesticides will have to be evaluated for each 
56 
crop under varying soil and climatic con- 
ditions, 
NEW APPROACHES TO 
NEMATODE CONTROL 
New approaches to chemical control of 
nematodes must be developed, particularly 
for controlling nematodes in and around living 
plants, In order to achieve these objectives, 
much additional knowledge is needed of the 
biochemical interactions between the nema- 
tode parasite and its plant host, Knowledge 
of the biochemistry involved in nematode 
parasitism of plants, which is being pursued 
at a number of institutions, may provide the 
basis for discovering new nematocides, such 
as systemics, repellents, andchemosterilants, 
The discovery of effective, practical 
systemic nematocides appears to be possible, 
Several chemicals, with at least some nemato- 
cidal activity, have controlled nematodes under 
experimental conditions (1, 7, 8, 11, 15, 17), 
Maleic hydrazide gives some control of root- 
knot nematodes when applied to the foliage, 
Some control of the bentgrass nematode, 
which causes nematode galling of seedheads, 
has been achieved by probable systemic activ- 
ity of the growth-regulating herbicides 
3-amino-1,2,4-triazole (Amitrole), 2-2- 
dichloropropionic acid (Dalapon), and maleic 
hydrazide when the chemicals were sprayed 
on the grass foliage before heading, 
Availability of commercial systemic nema- 
tocides will often eliminate many ofthe present 
difficulties experienced in fumigating soil, 
Application of systemic nematocides should be 
relatively simple, and they can be applied 
directly to the plant or to the soil near plant 
roots, which can take up the chemical, Sys- 
temic nematocides may reduce the need for 
present soil-fumigation treatments, because 
the plant itself: will disperse the nematocide 
in soil, 
Other profitable areas for research, yet to 
be thoroughly investigated, are repellents, 
attractants, and resistance inducers, The 
action of a repellent should be to disorient 
the nematode by disrupting the normal detec- 
tion processes used for finding plant roots, 
Such chemicals may be applied to plant foliage, 

