Ponul:G 



problem as does the estimation of cyst from samples of soil drawn 

 from bulk-sample, and exactly the same statistical principles apply 

 (see Tables 2 and 3)» Two methods may be adopted for the estimation 

 of the suspension: either the dropping apparatus of Jones (1911b') or 

 the modified McMaster slide of- Fenwick. The second method is the 

 simpler, and both are preferable to the hypochlorite method of Femjick 

 (I9U2). One disturbing feature of squash techniques is the failure of 

 egg masses to separate completely. This may be overcome by whizzing 

 the suspension in a food homogeniser (Bijloo 195U) to which various 

 "tools" have been added, e.g. plastic "pestle," rubber flail. 



None of the above methods give an indication of the viability of cyst 

 contents. This may be assessed by plying batches of cysts (not less 

 than l(XD) in suitable replication with root diffusates appropriate to 

 the species. This is usually done in solid watch glasses at constant 

 temperature. The method may be extended to give a usefiol separation 

 of those species which respond to root diffusates (Winslow 19^5)^ but 

 it does not work well with newly produced cysts. 



Estimation of hatchable larvae represents an additional steo in the 

 technique; and the more steps there are, the greater the variability 

 introduced. This can only be overcome by working with greater numbers 

 of cysts. The labour involved is, therefore, rather great. Moreover, 

 the hatching process is affected by the pre-treatment of cysts (Fenwick 

 I9I49, et seq.; Wallace 1955). Homeyer (19^3) tried to overcome this 

 by using acridine dyes and ultraviolet light to obtain d if ferential 

 fluorescence of living and dead eg.^^s and larvae. It has also been 

 noted by several workers that if eggs are "hatched" by pressure, the 

 living larvae emerging immediately adopt the natural straight or sinu- 

 ous outline of healthy larvae, while dead larvae remain kinked. De- 

 tails of this method with proffs of reliability have not yet been 

 published. 



If greater detail is required about the cyst population, recourse must 

 be had to the single cyst techniques of Gemell (I9U0), Ellenby (19U3)j 

 or den Ouden (1953)- These, however, are sometimes difficult to 

 interpret, since the larval hatches include many O's and require 

 transformation before they can be treated statistically. 



The above account follows the similar lines of an address given to 

 the Jubilee Conference of the Association of Applied Biologists (Jones 



1955). 



Anscombe, F. J. (1950). Soil sampling for patato root eelworm cysts. 



A report presented to the conference of advisory entomologists. 



Ann. appl. Biol, 37, 286-95. 

 Bijloo, J. D. (195U). A new method for estimating the cyst contents 



of the potato-root eelworm, Heterodera rostochiensis Wollen- 



wobnr. J. Ilolnrinth., 28, 123-2f>. 



