PUREE PIN OF Vr HE 
Se.) USDEPARTMENT OFAGRICULTURE % os 
No. 44 
Contribution from the Bureau of Plant Industry, Wm. A. Taylor, Chief. 
December 12, 1913. 
THE BLIGHTS OF CONIFEROUS NURSERY STOCK. 
: By CARL HARTLEY, 
Assistant Pathologist, Office of Investigations in Forest Pathology. 
INTRODUCTION. 
There has been a good deal of complaint from forest and orna- 
mental nurseries in various parts of the country of injury to conifers 
by blight. All cases in which trees in the nursery turn brown and 
die, in whole or in part, without any very definite symptom to indi- 
cate what caused death are classed as blight. 
The damping-off diseases and those caused by the rust fungi, de- 
tailed descriptions of which may be found in a bulletin by Spaulding, 
are not included under the name “ blight.” Damping-off attacks only 
very young seedlings, doing most of its damage during the first three 
weeks after germination. It is caused by several parasitic fungi 
which attack the soft tissues of the tender seedlings and rot them, 
often entirely destroying great aumbers of plants in a few days. 
Unfortunately one of these fungi sometimes continues to kill seed- 
lings for a time after they have become older and tougher, so that 
they look more as if they had been killed by a blight than by 
damping-off. 
Because of the difficulty in finding a natural dividing line be- 
tween the damping-off diseases and the blights, it has become neces- 
sary to draw an arbitrary line between them. All parasitic death of 
seedlings less than 2 months old will be classed as damping-off. The 
reason for this classification will be presented under the heading 
“ Root-rots.” The present paper will consider as blights only diseases » 
of stock more than 2 months old. Since the rust fungi are not com- 
mon in our nurseries and make their presence known before the 
death of the plant by swellings of the stems and by the breaking out 
of orange-colored spore pustules, there should be no difficulty in dis- 
1 Spaulding, Perley. The blister rust of white pine. U. S. Department of Agriculture, 
- Bureau of Plant Industry, Bulletin 206, 88 p., 2 pl., 5 fig., 1911. 
13745°—Bull. 44—13——1 
