Tecli. G:l 



ISOLATION OF NWATODES FROM SOIL 



Cyst-f onuing nematodes . 



A. Dry cysts will float at the surface of the water when added to the 

 soil sample. The material thus floating is poured, screened, 

 ladled off, or in some other manner removed, and then placed on 



a 25 mesh sieve nested with a 60 mesh sieve. Both sieves are then 

 thoroughly washed with water. The residue from the 60 mesh sieve 

 is washed off and then distributed in shallow layers in Syracuse 

 watch-glasses prior to searching for cysts under the binocular 

 dissecting microscope. 



The soil may be deliberately permitted to dry out or force dried in 

 order to get the cysts into the condition of being "floaters." 



B. Non-dry cysts , whether they float or sink, may be recovered from 

 non-dried soil by roiling the soil in a pail of water, allowing it 

 to settle briefly, and then passing the decanted suspension through 

 25 and 60 mesh sieves. The process is repeated until only sand and 

 gravel remain in the pail. The residue from the 60 mesh sieve is 

 examined for the presence of nematode cysts. 



It has been found that differential stain which colors the debris 

 and leaves the cysts unstained facilitates finding the cysts even in 

 lightly infested samples. (Taylor, A. L., J. Feldmesser, and 

 G. Fassuloitis, 1952) Stains siritable for this purpose are janus 

 green, brilliant green, malachite green, and gentian violet. The 

 time required for staining depends on the concentration of the 

 stain. Staining times of one hour are satisfactory with one gram 

 of janus green in h,000 ml. of water, one gram of brilliant green 

 or gentian violet in 32,000 ml. of water, or one gram of malachite 

 green in 6U,000 ml. of water. Staining overnight will require 

 solutions of one half these concentrations. 



Non-cyst forming nematodes in the soil should never be permitted to 

 dry out, because some species are killed by dessication, and, in 

 any case, the number of forms recoverable from the sample will be 

 reduced by drying. 



A. Baermann funnels will hold small volumes of soil from which the 



nematodes can be extracted, largely as a result of their own efforts, 

 as explained previously. Small samples can, therefore, be put 

 directly on the funnels without any previous treatment. 



Soil particles are most likely to settle into the funnel witliin the 

 first few minutes after adding the water and the soil. Per\nit these 

 particles to accumulate in the stem of the funnel, and after a short 

 period, draw off in a small volume of water and replace at the top 

 of the funnel. This practice will result in samples that are much 



