RUST

This term covers a group of fungi which attack a wide range of crops. Small, rusty spots, chiefly on the leaves (sometimes as with rose, rust on the undersides) are typical and very easy to detect. Infected leaves often drop to the ground, growth is checked and in some instances the plant is eventually killed outright. Black rust of wheat has been known for 2,000 years and occurs on the common barberry, Berberis vulgaris.

Rusts occur on anemones, antirrhinums, beet, blackberries, black currants, carnations, gooseberries, hollyhocks, mint, plums, raspberries, and violas, and are often difficult to control, although spraying with a thiram fungicide sometimes helps. Note that rust-resistant varieties of antirrhinum are available — see ANTIRRHINUM. It is of interest that antirrhinum rust did not appear in England until 1933, although recorded in the United States as far back as i860. Rose rust can be the most serious of rose diseases, even more devastating than black spot; see ROSE — Fungus Diseases.

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