Insect and Fungous Enemies of the Grape. 59 
TREATMENT. 
Spray as recommended for black- 
rot’ in the spray schedule (p. 74). 
The later applications are espe- 
cially important and should be very 
thorough. 
DEAD-ARM. 
Dead-arm of grapevines is caused 
by a wound parasite.** The organ- 
ism, having gained entrance to the 
trunk or branches of the vine, 
continues to grow and kill the 
tissues, forming a dead spot or 
canker, as shown in figure 66, 
and finally encircles the whole 
cane, causing the part of the vine 
beyond to die. Figure 67 shows 
a vine in which the fungus has 
attacked the trunk just above the 
two lower arms, causing the death 
of the whole upper portion of 
the plant. Cankers on dead areas, 
caused by the fungus, become more 
or less covered with the small 
black pustules or fruiting bodies 
which produce the spores of the 
fungus. 
Magnified views of these fruit- 
ing bodies and also of the va- 
rious spore forms which they pro- - 
duce are shown in the accompany- 
ing illustration (fig. 68). This 
fungus has three spore forms, two 
sometimes called summer spores 
and one winter spore’ form. 
Most of the new cases of the 
disease are apparently occasioned 
by the summer spores which 
are very abundant. The winter 
spore form is apparently rare in 
occurrence. 
Vie. 66.—Dead-arm canker on a young 
vine. The minute black pustules on 
the dead portion of the canker are 
fruiting bodies of the fungus. 
34 Oryptosporella viticola (Red.) Shear. 
