The photograph shows well, in a light red color, a field.section heavily 
infested with yellow rust and the plots unprotected by fungicide. In contrast, 
the healthy plots treated with fungicide appear in a darker red. 
Fungicide trial 
Winter wheat of the variety Joss Cambier was treated with the fungicide 
BAS 317 00 F in single and double applications of 3 kg/ha at two different 
times early in the summer of 1972. The evaluation was made on June 22, 1972. 
Densitometric evaluation 
  
The slide was measured using three different commercial instruments. Mean 
values from at least three to a maximum of 15 measurements/plot with white 
light and filters (red, green, blue) formed the basis for the statistical 
and biometrical calculation. To enable a better comparison of the instru- 
ments with each other and with the values from the evaulation on the ground, 
the light transmission was measured.Values for the opacity were transformed 
(7). 
Statistical evaluation 
A linear function of the type y - a « bx was adapted to the data with the 
aid of variance analysis and regression analysis. Here y represents the 
transformed test value of the densitometric evaluation, a the absolute value, 
b the regression coefficients and x the yellow rust infection. 
  
Discussion of the results 
  
Because the special false-color infrared film is used, the infrared radia- 
tion reflected by the plants becomes visible. As the intensity of this infra- 
red reflexion is an index for the healthiness of the plant, the densitometric 
evaluation of the intensity of the red can be used as the basis for an "eva- 
luation from the air". Applied to the attack by Puccinia striiformis this 
means that a high light transmission represents a heavily infected plot and 
a lesser light transmission indicates a healthy plot protected by fungicide. 
This relationship exists since the evaluation on the ground recorded a high 
infection in plots with high transmission and vice versa. 
Comparison of different measuring instruments 
A comparison of the individual measuring instruments with the aid of the 
results of the regression analysis with the sum of the evaluation values 
from the flag leaf and second leaf permits the selection of the most suitable 
instrument. It also permits statements on the reproducibility of measurements 
on an instrument.