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Hollyhock leaf disease #654663

Asked June 22, 2020, 5:48 PM EDT

Can someone tell me what is on my Hollyhocks and is killing them? How do I get rid of whatever it is?

Cecil County Maryland

Expert Response

Hi - It looks like your plants have symptoms of hollyhock rust, a fungal disease that is a common problem on hollyhocks grown in this area. There are some varieties such as Russian hollyhock and fig-leaf hollyhock that are considered more disease-resistant, but we do not have research on their performance. Planting a disease-resistant variety would be the best-long term solution to this problem.

The rust disease overwinters on infected plant debris and new spores form in the spring and move into newly emerging leaves. Because rust spores will continue to overwinter and return every spring, it is important to break the disease cycle to reduce hollyhock rust problems. Hollyhocks should be planted in areas with good air circulation. Good fall clean-up is important. Cut the plants back to ground level and remove any fallen leaves. Remove the plant material from the area. When watering, avoid wetting the foliage and place a 1-2 inch layer of mulch underneath the plants. Also removing the first leaves that have rust in the spring will help reduce the disease problem.

Fungicides are not effective once symptoms are already present like this. Fungicides are preventative and will not cure the leaves that are infected.
Refer to the following pages for more information.
https://extension.umd.edu/hgic/topics/rust-flowers-and-vines
https://hort.extension.wisc.edu/articles/hollyhock-rust/

Christa

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