Types of Garden Enemies
CEDAR-APPLE RUST (Gymnosporangium juniperi-virginianae).
This is general on red-cedars and sometimes on other junipers and is very common in home gardens where red-cedars and native flowering crab- apples have been inter-planted. Galls on the cedars are enlarged needles, varying from a fraction of an inch to 2 inches across. They are brown, round, or slightly kidney-shaped, and covered with small circular depressions from which in wet spring weather orange gelatinous spore horns are sent out (Figure 46). When covered with horns, the cedar gall is a very gay affair and may reach the size of a small orange. Winter spores embedded in the gelatin produce little sporidia which are carried by wind to apples and crabapples.
Fig. 45

By midsummer leaves of this host have circular orange-red spots each with a circle of tiny black dots on upper surface and there are wreaths or clusters of little brownish cups on the undersurface. The same cup-shaped fruiting bodies appear at the stem end of apples, sometimes on swollen crabapple twigs. The wind carries these summer spores from the apple back to junipers, where the galls take 18 months to mature and start a new cycle. The cedars are not much harmed by the rust, but apples lose their leaves prematurely and the fruit is dwarfed or deformed. All native crabapples are susceptible, with Bechtel's crab losing branches and sometimes dying. Oriental varieties are mostly resistant.

Control. Planning to keep the two hosts separated is best. Red-cedars are forbidden by law in some apple-growing sections. In home gardens cut galls off cedars in winter and early spring before they put out spore horns. Spraying apples regularly with Fermate and sulfur through spring and summer and spraying junipers with wettable sulfur in early spring and late summer control the disease but this is a more ambitious program than most home owners care to undertake.

Fig. 46

HAWTHORN RUST (Gymnosporangium globosum).
This is another cedar- apple rust, but the galls on the juniper host are a little smaller, seldom over 1/2 inch, and mahogany brown in color. Besides hawthorn, summer hosts include apple, crabapple, pear, and mountain-ash.

HOLLYHOCK RUST (Puccinia malvacearum).
There is no alternate host for a rusr that is coexistent with hollyhocks. Reddish to orange powdery spore pustules are formed on the underside of leaves and in elongated lesions on the stems. The upper side of the leaf is usually yellow in the areas over pustules, which sometimes turn grayish with production of sporidia Heavily infected leaves may wither. The fungus winters in old leaves and stems.




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