bel : ; 
Logbe 25 nm steps. At the same time, leaf transections were made, 
  
At preparated following the method of BRANSCHEID (1978), and 
PA examined microscopically. 
1ce- 
colour 
and Results and Discussion 1, 
2 pho- 
At 
esta- The results of the soil water and nutrient content deter- 
in minations showed, that the slackening of the plants was not 
atode primarily caused by nutrient deficiency and could not be cor- 
sting related to lack of water as compared to the surrounding turgid 
depth areas. 
S Two typical examples of the results obtained from different 
ies laboratories and methods investigating aliquots of the same 
he samples for cyst nematode populations are given in Figures 1 
modus and 2. Not only do the results from the different methods 
. differ to a large extent, although they are claimed to be 
the comoarable, but also those of the same methods (Fenwick a and 
b). In a few cases, soil results from severely infested field 
parts as confirmed by the high number of cysts at the plants” 
roots, showed no or negligible nematode occurence. The questi- 
on arises how from such results recommendations for control 
actions are to be derived. Moreover, the soil tests give no 
hint as to the distribution of the infestation patches in an 
individual field, so that partial control measures cannot be 
realized. 
o. The results of the spectrophotometric measurements showed 
that in the wavelength interval of 500 - 950 nm, which 
corresponds approximately to the sensibility of the film used 
together with Wratten filter no.12, differences between the 
the Spectral reflectance of turgid leaves from non-infested plants 
sults and slackening leaves from nematode-infested plants are so 
slight (max. 1.5 per cent) that they cannot possibly be 
ted and recorded by the emulsion (Figure 3). Leaf transections, how- 
measur- ever, showed differences in mesophyll structure: the spongy 
n ince- 
H 
) for more detailled numbers and figures see SANWALD (1979)