Orange Rust Plant Pathology Orange Rust Orange rust is a serious disease of brambles. Black and purple raspberries are susceptible, as are most varieties of blackberries. Orange rust does not occur on red raspberries. The new shoots of infected plants appear weak and spindly as they emerge in the spring.
Leaves are small, yellowish, and sometimes misshapen.
Infected leaves eventually wither and fall. Canes may appear to partially recover during the growing season, but the plant is still diseased. The orange rust fungus is systemic, meaning that it grows throughout the roots, crown, and shoots of an infected plant. Infected canes often appear bushy, bearing little or no fruit. Infected plants cannot be cured.