NEMATOCIDES IN PLANTS AND SOILS 
A. L. Taylor! 
The search for nematocides started more than 80 years ago, and one nematocide was 
in limited use before 1900. The first nematocide was placed on the market in the United 
States in 1937. This was followed by another about 1940, both suitable for only limited 
use in greenhouses and vegetable seedbeds, The rapid advance in the use of nematocides 
started about 1946 when materials suitable for field use became generally available. Use 
has grown to over a half million acres in 1959, Most of the treated land has been planted 
to tobacco, vegetable, or pineapples, though nematocides are used for a variety of other 
crops. 
The chemicals most widely used as nematocides are ethylene dibromide (EDB), 
1,2-dibromo-3-chloropropane (DBCP), and 1,3-dichloropropene, obtainable either as 
technical dichloropropenes, or mixed with 1,2-dichloropropane (D-D mixture). These are 
formulated with naphtha and other diluents, may contain emulsifiers, or be adsorbed on 
clay for application in granular form. These are often used in fields which are planted to 
vegetables, pineapples, or other edible crop plants. 
Normal application rates for mineral soils range from 54 to 108 lbs. per acre for 
EDB, 17.6 to 88 lbs. for DBCP,and100 to 200 lbs. for technical dichloropropene or 200 
to 400 lbs. for D-D mixture. 
These materials are most efficiently applied by injection into the soil at a depth of 
6 to 8 inches in rows 12 inches apart over the whole field. An alternative method is to 
apply the nematocide to only the planting rows and leave the middles untreated, Since 
these materials are fumigants, the fumes diffuse in all directions from the application 
rows and kill nematodes in the upper 18 inches of soil. 
All these nematocides are more or less toxic to plants when applied to the soil, but 
after a period this effect is no longer noticeable, depending on the chemical, the crop 
plant, and the soil type. EDB and dichloropropene are toxic to most kinds of plants for 
several days or two weeks after application. Some crop plants such as cotton are not 
injured by DBCP and can be planted immediately after application, On the other hand, 
tobacco might show injury from DBCP even if planted several months after application. 
Ethylene dibromide leaves in the soil a residue containing bromine, which is taken 
up by various plants. In one experiment, tobacco and tomato plants grown in soil fumi- 
gated with EDB contained 4 to 50 times as much bromine as plants grown on the same 
soil not fumigated, The lower concentration was found in plants grown in loamy sand and 
the higher rate in plants grown in clay. Drying of the soil after fumigation affected the 
bromine content of the plants very little. This was interpreted as indicating that the 
bromine was present in inorganic form (Brown, et al., 1958). Another report indicates 
that the bromine is in the sorbed phase, the sorption being closely related to the surface 
area of the soil and also to the organic matter, moisture and clay contents (Call and 
Hague, 1957). 
In an experiment in Virginia, peanut hay from plots treated with EDB contained 243 to 
352 p.p.m. of bromine as compared with 25 to 60 p.p.m. in hay from adjacent untreated 
plots. When the hay from the treated plots was fed to cows for 4 weeks, there was a rise 
to a maximum of 109 p.p.m. of bromine in the milk (Young et al., 1955). 
1Nematologist, Crops Research Division, Agricultural Research Service, U.S. Department of Agriculture, 
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