SPORES IN THE UPPER AIR* 
By Elvin C. Stakman, Agenty Office of Cereal Investigations^ and Plant Pathologist, 
Agricultural Experiment Station, University of Minnesota, and Arthur W. Henry, 
Gordon C. Curran, and Warren N. Christopher, Field Assistants, Office of 
Cereal Investigations, United States Department of Agriculture'^ 
INTRODUCTION 
As a part of the rust-epidemiology investigations which have been 
made since the spring of 1917 by the Office of Cereal Investigations of 
the United States Department of Agriculture in cooperation with several 
State experiment stations, attempts have been made to get as much 
information as possible on the dissemination of spores by air currents 
and to correlate the data with the spread of rust on host plants. The 
usual method in studying the distribution of spores of pathogenic fungi 
by wind has been to expose spore traps of various kinds near the surface 
of the earth. The possibility of spores being carried to higher altitudes 
by convection currents, whirlwinds, and other air movements has been 
recognized, and spore traps have been exposed on high buildings, on 
mountain tops, and other elevated points. However, it is desirable to 
know how many spores there are in suspension several thousand feet 
above the surface of the earth. 
During the spring and summer of 1921 ^ spore traps ^ were exposed on 
airplanes ® in the hope of obtaining more information on the dissemina¬ 
tion of aeciospores and urediniospores of Puccinia graminis and other 
rust fungi. The general results seem *to be worth recording, although 
the problem of rust epidemiology was not solved. 
METHODS 
Airplanes were used in preference to balloons, kites, or other similar 
devices, because long distances could be covered in a short time, spore 
traps could be exposed easily at different altitudes, and the direction of 
flight could be changed at will. 
Ordinary microscope slides (3 inches by i inch), smeared lightly with 
vaseline on one side, were exposed in different ways. One method was 
* Accepted for publication Aug. 21, 1922. 
* The authors wish to acknowledge the enthusiastic cooperation of the commanding ojfficer at Kelly Field, 
San Antonio, Tex.; Maj. Ir^’ A, Rader, air officer for the Seventh Corps Area of the United States Army, 
at Fort Crook, Nebr.; Mr. W. I. Votaw, manager of the Aerial Mail Service Station at Omaha, Nebr.; and 
Mr. W. A. Kidder, of fJhe Curtiss Flying Field (private), St. Paul, Minn. The authors are under deep 
obligation to these men, and to the pilots working under their direction, for their generosity and courtesy. 
* The manuscript containing the results obtained in 1921 was submitted for publication before the 192a 
results were available. On account of the delay in publication it has seemed desirable to include a few of 
the most important results obtained in 1922, although details are not given. 
* The mechanical spore trap was devis^ by G. D. George, of the Office of Cereal Investigations and the 
University of Minnesota. 
The Air Service erf the United States Army furnished the planes and pilots for the flights. The follow¬ 
ing men assisted in the work for the U. S. Department of Agriculture: E. B. Uambert, E. H. Ostrom, * 
J. J. Oiristensen, D. U- Bailey, Wallace Butler, and S. P. Harter. 
(599) 
Journal of Agricultural Research, 
Washington, D. C. 
aef 
Vol. XXIV, No. 7 
May 19, 1923 
Key No. G-304 
