cedar apple rust

August 22, 2019August 22, 2019

Cedar-Apple Rust

Figure 1. Cedar-apple rust gall on eastern red cedar showing thoroughly wetted, gelatinous spore-bearing structures. (Alan R. Biggs, West Virginia University)

Cedar-apple rust is a fungus disease of apple and cedar and spends parts of its life cycle on each host. It is caused by Gymnosporangium juniperi-virginianae. The fungus can infect leaves and fruit of most cultivars in the eastern region. A notable exception is ‘Delicious’, which is nearly immune.

The most conspicuous symptoms on apple are bright orange, glistening …

August 22, 2019August 22, 2019

Table of Juniper, Hawthorn, and Crab Apple Resistant to Rust Diseases

Cedar-apple rust is a fungus disease of apple and cedar and spends parts of its life cycle on each host. It is caused by Gymnosporangium juniperi-virginianae. The fungus can infect leaves and fruit of most cultivars in the eastern region. This table lists juniper, hawthorn, and crab apple cultivars with resistance to rust diseases.

Juniperus (Juniper)	Crataegus (Hawthorn)	Malus (Crab Apple)
Cedar-apple and hawthorn rust resistant	Cedar hawthorn rust resistant	Cedar hawthorn rust resistant
J. ashei	C. crus-galli	‘Adams’

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August 22, 2019August 22, 2019

What causes the yellow leaf spots that later develop a brown center on my apple leaves?

This a fungal disease called cedar-apple rust. Cedar-apple rust is a common disease of apple and crabapple. The fungus that causes the disease, Gymnosporangium juniperi-virginianae, is unusual because it must spend a phase of its life cycle as a parasite on Juniperus species, such as red cedar or ornamental junipers. Control: Grow resistant apple or crabapple varieties. Apple varieties that normally show good to excellent resistance to cedar-apple rust include ‘Red Delicious’, ‘McIntosh’, ‘Arkansas Black’, ‘Winesap’, ‘Mollies Delicious’, ‘Spartan’, …