465 
The early recognition of fire-blight by means of remote 
sensing techniques therefore appears not possible. Investigations, 
however, show a new solution for classification of general vege 
tation by comparison of density differences between different 
spectral bands. Probability of objective interpretation can be 
increased by using more spectral bands, i.e. by refinement of 
the step method. 
This method requires calibrated radiometric sensors in 
stead of photographic sensors, whose different images are hard 
to be correlated because of the lack of uniformity concerning 
the exposure time, the film layers and the film processing. 
We appreciate the technical help in this investigations of 
Mr. HELBIG, Dr. MOZER and Mr. STOIBER with DFVLR, Oberpfaffenhofen. 
LITERATURE 
Billing, E. 
Crosse, I.E. 
Garrett, C.M.E. 
1960: Laboratory diagnosis of fire-blight and 
bacterial blossom blight of pear. Plant 
Pathology 9, 19. 
Lelliot, R.A. 
1968: Fire-blight in England. Rep. Internat. Conf, 
on fire-blight EPPO Publications Ser. A 
No. 45-E, p. 10-16, Paris. 
Fischer, H. 
Meyer, J. 
1972: Praktische Erfahrungen bei der Bekämpfung 
der Feuerbrandkrankheit (erwinia amylovora) 
1971. Gesunde Pflanzen, 24 Jg., April 1972 
Heft 4, D 3249 E, p. 62-71. 
Beer, S.V. 
Aldwinckle, H.S. 
1974: Fire-blight in New York State. New York's 
food and life sciences, Vol. 7, No.1, 
Jan.-Mar. 1974, p. 16-19.