40 
CoLOh’ADo Experiment Station 
Rust (Uromyces appendiculatus) (36) — Bean rust is common in 
Colorado although it usually appears too late in the season to do 
much damage. In favorable years, however, it may appear suffi- 
ciently early to be rather destructive. 
Small, raised, rusty-red, powdery spots are formed on the leaves 
commonly on the lower surface. These spots are pustules contain- 
ing thousands of small reddish-brown spores which are scattered by 
wind and rain to healthy plants where they germinate and cause 
more spots. The disease interferes with the food making processes 
of the plants and decreases its vitality. Late in the season the 
reddish-brown spores are replaced by black ones which are suf- 
ficiently hardy to live over the winter. The disease is a difficult one 
to control. Since the black spores, formed on the leaves, carry the 
fungus over winter the destruction of affected vines should tend 
to lessen the amount of disease. 
Certain varieties are said to be more resistant than others, but the 
question is one that needs further investigation. 
Sunscald — A non-parasitic disease greatly resembling bacteriosis 
is common in Colorado. The brownish spots and streaks which 
resemble so closely the bacterial spots are the result of burning or 
scalding by strong sunlight. Sunscald is not of much economic 
importance as it produces no appreciable reduction in yield. 
BEET 
Root Rot (Rhizoctonia sp.) — ^Both garden and sugar beets are 
subject to root rot. The disease first becomes evident by a drooping 
and wilting of the leaves. On examination the outer leaves are 
seen to be rotted at the base. This decay soon spreads into the crown 
and root causing the infected area to turn brown. Cracks often 
appear and in severe cases the entire beet may be destroyed. 
Moist weather and excessive irrigation favor the development of ^ 
the disease. The fungus causing the disease lives from year to 
year in the soil. Careful irrigation and crop rotation are the most 
practical means of reducing the loss from root rot. 
Curly Top (38), (39) — Curly top is one of the most destructive 
diseases of the sugar beet, especially in the western beet fields. It is 
characterized by an inward curling of the leaves, checked growth and 
the production of an abundance of hairy roots. 
Curly top is produced by the bite of the sugar lieet leaf hopper 
(Eutettix tenella). The bite of the insect is not sufficient to i)rodiice ^ 
the disease, but the insect cari’ies within its system some substance j 
