HOLLYHOCK RUST 
This is a rust disease peculiar to a number of malvaceous hosts. It is 
indigenous to Chili where it was discovered in 1852. It is especially 
destructive to the hollyhock and is now known as a common disease of 
this perennial in nearly every temperate country of the globe. 
SYMPTOMS 
The lesions of this disease occur on all the above-ground parts of the 
host, but are usually most numerous on the leaves. In severe cases, the 
calyx and seed-capsules are affected. 
On the leaves. Examine the specimens provided and OBSERVE :— 
1. The cushion-like pustules scattered over the leaf-surface,— 
sori of the pathogene; most abundant on which side? 
2. The variations in size and shape of the sori. 
8. Color. This varies with the age of the lesion. The youngest 
lesions usually show a distinct bright-yellow color, especially on the upper 
surface or where they occur on the veins and petioles. A little later the 
fully developed sorus (telium) takes on a rusty brown color and is sur- 
rounded by a yellowish zone. When the spores of the telium begin to 
germinate, the color becomes a grayish brown. As the pustule dies it 
turns black. . 
4. The thickened character of the leaf-tissue in well developed 
lesions; there is slight hypertrophy. 
5. In old lesions, the dead and shriveled sorus surrounded 
by a narrow zone of necrotic leaf-tissue. This dead tissue sometimes falls 
out, leaving small round holes in the leaf-blade. 
DRAW a diseased leaf to show the characters of the lesions at various 
stages. ; 
Where the lesions are very numerous, the entire leaf-blade withers, 
turns brown and finally falls from the stem. ‘The general effect of a 
severe infection is best observed in the field. 
On the stems and the petioles. Examine the specimens provided. 
OBSERVE :— 
6. The shape and size of the pustules; usually larger than 
those on the leaves. Why? 
7.. The elongated dead zone about the older lesions. How deep 
does the lesion extend? The lesions are very limited. They frequently 
dry out and disappear except for a large oval scar left by the healed wound. 
DRAW several stem-lesions. 
On the fruit. Study the lesions on the flowers provided (best studied 
on the fruits of Malva rotundifolia L). OBSERVE :— 
8. The lesions on the calyx; compare with those on leaves and 
stems.. 
9. The sori on the seed-carpels; color, size and location. ‘DRAW. 
The pathogene is often distributed on seed infested in this manner. 
ETIOLOGY 
The hollyhock rust is caused by a uredinaceous fungus, Puccinia 
Malvacearum Montagne. 
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