July i f 1918 
True Nature of Spinach-Blight 
3 
changes in appearance. The following is a description of the appear¬ 
ance of the plant at each stage of the disease : 
Stage 1.—Plants in this stage may be distinguished from the healthy 
plants by a very slight yellowing which generally occurs on the younger 
leaves or those which are not fully opened. Occasionally a slight yel¬ 
lowing may be noticed on one or more of the older leaves; otherwise the 
plant is in a vigorous growing condition and still retains a normal dark 
coloration (PI. 4, A). 
Stage: 2.—Plants in the second stage of the disease have a more pro¬ 
nounced yellowing on the younger leaves than those in stage 1. The 
plants are usually vigorous, and no marked changes are to be noted in 
the older leaves. Occasionally the younger leaves begin to show evi¬ 
dence of being malformed. This, however, is not usual in this stage. 
Stage 3. —This stage is characterized by the appearance of malfor¬ 
mation in the younger leaves. They become much wrinkled and nar¬ 
rowed and show decided mottling. The yellowing has usually spread to 
many of the older leaves. Plants in the third stage of blight are gen¬ 
erally not as large as healthy plants of the same age. 
Stage 4.—Plants in this stage show a distinct evidence of stunting; 
the yellow color has spread over the entire plant, and the older leaves are 
distinctly mottled. The younger leaves, while still growing to a certain 
extent, are so malformed as to be hardly recognizable as spinach leaves. 
They are very finely savoyed and have a feathery appearance. They 
do not curl to any great extent. The plant has lost most of its vigor by 
this time, and little growth takes place after this stage. 
Stage 5.—The fifth stage is characterized by the disintegration of 
tissues, usually shown by a browning and dead appearance of parts of 
the older leaves; the browning usually occurs on the outer tips first and 
works inward as the disease progresses. The younger leaves may 
become wholly yellow. This color is lighter in the fall and winter than it 
is in the spring, when it occasionally shows as deep orange-yellow. The 
mottled appearance of the older leaves at this stage is very striking; 
such chlorophyll as remains is gathered along the veins, leaving the 
tissues between the veins a pale-yellow color. The older leaves become 
wrinkled and lose much of the deep savoying characteristic of healthy 
leaves. 
Stage 6.—The sixth stage (PI. 4, B) is characterized by the total 
disintegration of the older leaves; they become brown and lose turgidity, 
often being supported only at the point of attachment, the remaining 
portions resting almost entirely on the ground. About this time the 
central leaves of the plant begin to turn brown. The older leaves pass 
from a brownish yellow to a more or less translucent brown or straw 
color. 
