Distinguishing between the two causes of orange coloration on leaves is important. The first possible causeis late leaf yellow rust. It occurs on both the undersides of leaves and on fruit in cool, damp weather, especially in autumn.
The upper leaf surface may develop yellow blotches, curl upwards and turn brown when infected.
The second possibility is much more serious. Orange rust is systemic and infects all plant parts of black raspberries and blackberries. Symptoms are most apparent in spring when the undersides of leaves turn orange and new primocanes are strap-like.
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