AIR AND WIND DISSEMINATION OF ASCOPORES OF 
THE CHESTNUT-BLIGHT FUNGUS 
By F. D. Hearn, M. W. Garpner, and R. A. STUDHALTER, Agents, Investigations in 
Forest Pathology, Bureau of Plant Industry! 
HISTORICAL INTRODUCTION 
Wind dissemination of the chestnut-blight fungus (Endothia parasitica 
(Murr.) And.) was first suggested by Murrill (13) ? in 1906, although he 
apparently had only the pycuospores in mind, as is shown by the follow- 
ing quotation: 
Later the fruiting pustules push up throtgh the lenticels and give the bark a rough, 
warty appearance; and from these numerous yellowish-brown pustules millions of 
minute summer spores emerge from day to day in elongated reddish-brown masses to 
be disseminated by the wind and other agencies, such as insects, birds, squirrels, etc. 
A few years later, in a discussion of the means of spreading the disease, 
Hodson (9) says: ‘ 
Wind is probably the principal agency, but the spores are no doubt carried by ani- 
mals, birds, insects, and by shipment of infected material. 
He also cited some observations to substantiate the wind-dissemination 
theory, but it was not brought out clearly whether he had in mind the 
ascopores or the pycnospores only. A similar opinion is expressed by 
Mickleborough (12) a little later. After speaking of both the ascopores 
and the conidal, or summer, spores, he states: 
The minute spores are carried by the wind, on the feathers of birds, and the fur of 
squirrels. 
Referring to the spore horns, Mickleborough writes: 
These threads are dissolved and washed away by the rain and the spores are blown 
about by the wind. 
There are two possible ways in which pycnospores might be dissem- 
inated by the wind: First, by the direct transport of spore horns or small 
fragments of these structures; second, by the transport of dust particles 
bearing spores previously washed down by rains. 
Fulton (4) reports experiments which indicate that the former method 
of transport of pycnospores is of little importance in the spread of the 
disease. He concludes his discussion of this topic with the following 
statement : 
It seems likely the detachment was largely of small bits of the tendrils made up of 
large numbers of spores, and that these are too heavy to be carried great distances; 
1 ‘The writers received valuable assistance in this work from Mr. R. C. Walton, also an agent, Investi- 
gations in Forest Pathology. ; oor 
2 Reference is made by number to “ Literature cited,” p. 525-526. 
Journal of Agricultural Research, Bie eS 6 
Dept. of Agriculture, Washington, D. C. pai x 
(493) 
