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JOURNAL OF ECONOMIC ENTOMOLOGY 
[Col. 17 
June or July to October as we secured by the older and more careless 
method of crop rotation in two or three years. In every case where 
the method has been carefully applied it has reduced the nematodes to a 
point where it was possible to profitably grow highly susceptible plants 
such as okra thruout the succeeding trucking season. 
Soil Fumigation 
Seed beds present another problem calling for more complete eradica¬ 
tion of nematodes, particularly in the case of crops like celery or lettuce, 
which are planted in the summer when nematodes are most active. 
On the other hand, the limited area and the high value of the crops, 
justifies more expensive methods. Undoubtedly, steam or hot water is 
the most effective method of ridding the soil of nematodes, and where 
the trucker has steam handy it is undoubtedly the most satisfactory 
method of treating seed beds, but unless the land is piped for steam we 
have found steaming a very expensive process. It was tried on the 
pineapple lands of the East Coast but the cost was prohibitive. The 
same objection applies to hot water. The expense involved was largely 
that of transporting the boiler or other outfit from place to place. 
We have tried carbon bisulphide and formalin and find them very 
good soil fumigants for nematodes, but on the whole we have had 
the best success, considering the cost, with a double treatment of sodium 
cyanide and ammonium sulphate. This was first tried, so far as the 
speaker knows, a number of years ago in California by Professor Wood¬ 
ward on a small scale. In practice, the soil is first saturated with a 
solution of sodium cyanide in water. We find that the dosage required 
will vary much with the type of soil. In general the lighter the soil 
the smaller the dosage required. On the sandy soils of the average 
trucking regions of Florida we have found that 600 pounds of sodium 
cyanide per acre is usually sufficient. This is applied in water and 
washed down with a liberal irrigation (most seed beds in Florida are 
provided with overhead irrigation.) Ammonium sulphate is then 
added at the rate of 900 pounds to the acre. This is also washed down 
with a light irrigation. The ammonium sulphate acts on the sodium 
cyanide producing hydrocyanic acid gas. We find this method very 
effective, not only in killing out the root-knot organisms, but all animal 
life in the soil is killed. The seeds of most weeds are also killed, but 
those with large, heavy seeds will usually survive the treatment, as 
will also heavy Bermuda grass sod. Of course, covering the ground with 
some gas tight material, such as tarred paper or a cloth treated with 
