April, ’24] 
WATSON: NEMATODE CONTROL 
229 
rubber (we have found the material from which the tents for fumigating 
citrus trees are made to be very satisfactory) will greatly increase the 
killing effects of the fumigation and reduce the dosage necessary. 
The expense of this treatment is high. It costs nearly $200 per acre, 
but as the acreage is usually small the above expense is not prohibitive 
for seed beds. The residue, of ammonium sulphate, left in the soil 
increases the soil fertility and causes rapid growth of the plants. 
We find that we can ordinarily safely plant the soil in ten days to 
two weeks after treatment. We have tried the sodium cyanide alone 
without the ammonium sulphate but the results were not nearly as 
satisfactory. The evolution of gas was not sufficiently rapid and the 
cyanide remained in the soil for a considerable time. It was difficult 
to get rid of it. 
We are now experimenting with calcium cyanide, both in the form 
of dust and flakes. It would seem that we will be able to substitute 
this material for the sodium cyanide and ammonium sulphate at a 
greatly reduced cost. We have found the most satisfactory method of 
applying this material is to sprinkle it in the furrow when the land is 
plowed. 
Drowning 
It has long been observed that lands regularly kept under water for 
several months each summer were never seriously affected by nematodes. 
The flooding of the Everglades last year offered us opportunity to secure 
some data on the length of time necessary for eradication of nematodes. 
We found that soils continually under water for as much as six weeks 
still had plenty of nematodes, but fields submerged for four or five 
months were in all cases free. It would seem as if the time necessary 
to drown out the nematodes is too long to make this method of much 
practical benefit. 
Mr. R. A. Cooley: I would like to ask if the cyanide treatment of 
the soil had any effect on the soil organisms ? 
Mr, J. R. Watson: It did not seem to have much effect. 
Mr. H. F. Dietz: I would like to ask Mr. Watson if he has had any 
experience in getting perennial plants to outgrow the nematodes. This 
is a problem which I think will be important in the next few years, 
especially in connection with hardy perennials. 
Mr. J. R. Watson: We are running tests along these lines but thus 
far they have not been very satisfactory. 
