Hollyhock Spotted and Dying Leaves
Another question on behalf of a neighbor; her favorite hollyhock is in bad shape. Because the damage to the leaves result in small spots, could it be insect damage rather than fungus? Aphids? Or is there a non-insect disease that could cause this kind of damage? Whichever it is, what would be her best course of treatment to save her hollyhock? Thanks, Jack
Frederick County Maryland
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 in infected plant debris and new spores form in the spring and move into newly emerged 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.
You are welcome.