Hollyhock

July 15, 2017

I need help! My hollyhocks are dying at the base and they have these yellow spots all over them. Is it an aphid? What can I do to save them and stop the spread?

I would say you have a bad case of hollyhock rust.  Hollyhock rust tends to become more severe as the summer progresses, and has hit early this year with all the rain and humidity.  When you have the disease on a plant spores are carried to other plants by splashing rain and wind.  Sanitation is critical.  Clean up as many diseased plants as you can and spray your healthy plants with a product containing chlorothalonil (Daconil or Bravo) or myclobutanil (Immunox).  This fall make sure you cut back all the old foliage to the ground and dispose of it.  If you have had this problem in the past, be proactive and spray when the plants begin growing to prevent infection.  Once you have a disease firmly entrenched in a garden it is hard to control it.

May 2012

I am growing my first hollyhock flower bed and my plants are afflicted with a light green serpentine leaf ailment. My next door neighbor (one-quarter mile away) has the same problem but with brown crusties on the underside of the leaf. Can you give us a name or a treatment?

The problem is called a leaf miner. Think about how small the insect has to be to get between the layers of the leaves and make a tunnel. While it isn’t the most attractive part of the plant, it tends to be more of a cosmetic problem, since the plant continues to grow and bloom. If only a few leaves are affected, simply remove them and destroy them—don’t throw them on the ground, the larvae of the insect may still be inside. If the damage gets worse, you can use insecticides, but once the insects are firmly established, they are more difficult to control, and control is often unnecessary. Do a good job of cleanup in the fall to start next year clean.

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