286 



Journal of Agricultural Research 



Vol. VI, No. 8 



yellow-pine reproduction, especially on south slopes under mature cover, 

 was observed to be turning brown and in many cases dying. On exam- 

 ination the needles of these seedlings showed that they were infected 

 with H. deformans. This is a grazing region, and the forest has been 

 continuously grazed by large bands of sheep for many years. The 

 stems of the young pines in numerous cases bore near their bases one or 

 more wounds of a shape and nature indicating that they were produced 

 by the treading of grazing animals. Since little information is at hand 

 on the effects on forest production of wounding by grazing animals, it 

 seemed worth while to make a detailed study of the case so far as time 

 would allow, with the double object of determining which injury — viz, 

 the needle fungus or the wounding — was responsible for the sickly con- 

 dition of the young pines. It must be remembered, however, that the 

 seedlings were growing under the canopy of a mature yellow-pine stand; 

 consequently they were not growing rapidly in height. Four one-tenth- 

 acre plots were laid off on representative south slope sites and every 

 seedling on the plots carefully pulled up and bound in bundles. These 

 bundles were sent to the laboratory and afterwards carefully diagnosed. 

 The normal condition of root system and crown and general vigor of 

 seedlings were judged from a knowledge of normal young pines of the 

 same age, free from disease and wounds, growing in the same regions and 

 under the same slope conditions. The results of this study were em- 

 bodied in a preliminary table from which Table I was condensed as being 

 more readily undestandable. 



Table I. — Number of seedlings on 4 one-tenth-acre plots, average age and height, con- 

 dition of infection with Hypoderma deformans, present condition of wounding and root 

 system, south-slope type 



DISTRIBUTION OF HYPODERMA DEFORMANS 



The disease of yellow-pine needles caused by H. deformans is widely 

 distributed throughout the northwestern part of the United States 

 and western Canada. Its distribution in other parts of the West 

 is not known, although the fungus has undoubtedly been collected 



