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- of new 
In order to apply those pest control techniques effectively 
from biological, environmental, and economic points of view, 
nematode occurence and the extent of damage in individual fields 
must be known. As the accuracy of conventional methods, by 
which the nematode population density is determined by investi- 
gation of soil samples (FENWICK 1940, BEHRINGER 1976) has been 
found to be doubtful (KÜSTERS 1976), new ways for damage inven- 
tory had to be looked for. Remote sensing techniques have 
repeatedly been proven to be a valuable means for the assessment 
of crop damage (BRENCHLEY and DADD 1962, BRENCHLEY 1966, 
GAUSMAN 1971, GAUSMAN et al. 1975, HEALD et al. 1972, WALLEN 
and JACKSON 1975, ARNETT 1976). As the first outcome of a 
provisional test applying aerial infrared photography was 
promising with respect to our problem (REICHERT 1975), detail- 
led investigations were carried out. 
Materials and Methods 
The test sites for our two years'experiments were located at 
important West German sugar beet growing areas: (1) the fertile 
parabrown soil area west of Cologne; (2) the alluvial plains of 
the Rhine river south of Francfurt; and (3) the loess-soil 
region of Rhino-Hassia. The lengths of these sites were 5, 15, 
and lO km, respectively. They extended in north - south direction 
and were of flat topography save the third one, whose terrain 
is slightly undulated with height differences of up to ca. 50 m. 
Aerial photography was conducted with a twin-engine aircraft 
carrying a Zeiss metric camera loaded with Kodak 2443 infrared 
colour film. Focal length of the camera lenses employed were 
153 and 305 mm. Photographs were taken at scales of l : 5.000, 
1: 7.500, and 1 : 10.000. Different forward overlaps of 80, 
60, and 20 per cent were tried, and a 20 per cent overlap at test 
site (3), where two strips were flown. Image interpretation was 
done visually using a 8x magnifying stereoscope, or a 8x magni- 
fying lens. Furthermore, densitometric measurements were carried