140 ASPARAGUS 
taking up nourishment and causing an enfeebled con- 
dition of the victim, which results in loss of the green 
color and the final rustiness of the plant, due to the 
multitude of spores formed upon the surface. These 
spores are carried by the wind to other plants, where 
new disease spots are produced; but as the autumn 
advances a final form of spore appears in the ruptures 
that is quite different in shape and color from the first 
ones produced through the summer. The spores of 
late autumn, from their dark color, give an almost 
black appearance to the spots. 
There is another form which the rust fungus assumes 
not usually seen in the asparagus field, but may be 
found in early spring upon plants that are not subjected 
to cutting. This is the cluster-cup stage, so named 
because the fungus produces minute cups from the 
asparagus stem, and in small groups of a dozen to 
fifty, making usually an oval spot easily seen with the 
naked eye. This stage of the fungus comes first in 
the order of time in the series, and is met with upon 
volunteer plants that may grow along the roadside or 
fence row, or in a field where all the old asparagus 
plants have not been destroyed. } 
METHODS OF TREATING THE RUST 
All the cultivated varieties of asparagus are readily 
affected by the rust, although it has been found that 
some varieties, notably Palmetto, are less susceptible 
to its attacks than others. The most effectual means 
of controlling the disease are spraying, burning of the 
brush, cultivation, and irrigation. 
Spraying.—Dr. Halsted, in his first experiments, 
