If your hollyhocks are affected by mallow rust, you must act quickly. Because the fungal disease can spread throughout the garden.
Anyone strolling through a cottage garden will definitely find one plant here: the hollyhock (Alcea rosea). These roses grow up to 2 meters high and fit perfectly into a cottage garden with their many colorful flowers. Of course, it only looks beautiful when it is thriving. That is usually the case. Nevertheless, it can also happen that she is attacked by an illness. And one thing is particularly destructive: we're talking about mallow rust.
Which plants are affected?
Mallow rust is a fungal disease that can occur as early as spring. So when the first foliage has formed. This fungal disease affects not only hollyhocks, but also other mallows and summer flowers. Examples include silver linden, hibiscus and cup mallow.
How do you recognize an infestation?
Hollyhocks immediately captivate everyone with their beauty. But once the mallow rust has struck, it quickly puts an end to the beauty. When infested, the leaves are covered with brown to yellow spots on the upper side of the leaf and reddish spots on the underside that look like pimples or pustules. That alone doesn't look nice. If the infestation is severe, the leaves will also turn brown and die. If they then fall to the ground and are not disposed of in good time, the mallow rust affects other, neighboring plants.
Causes of mallow rust infestation
Often you bring mallow rust into your home when you buy a young plant. When buying a plant, always make sure that it does not have any damage or stains. However, mallow rust often breaks out when the leaves of the plant are always damp and cannot dry off.
4 tips to prevent mallow rust
» Tip 1: Cut back plants!
If you want to do something to prevent mallow rust, you should cut the plants down close to the ground in autumn, dispose of all plant remains and pile up the earth around the plants. However, it is important that youDo not dispose of plant remains in the compost, but with household waste so that the fungal disease cannot spread.
Alternatively, you can also work with bark mulch. But you have to remove this again in the spring.
» Tip 2: Provide plants with nutrients!
Mallow rust occurs mainly in biennial and perennial hollyhocks. A good supply of nutrients supports the he alth of the flowers. So keep fertilizing with mature compost.
» Tip 3: Do not water over the leaves!
In addition, it is important that you water the mallow plants at the bottom so that the leaves are largely protected from moisture.
» Tip 4: Keep planting distances!
When planting, always make sure there is a generous distance between the plants so that the air can circulate well and damp leaves can dry out more quickly.
Fighting mallow rust
As soon as the distinctive spots appear on the leaves in spring, you must cut them off immediately and dispose of them. It is then advisable to treat the leaves with a manure made from ferns. To do this, put a kilogram of fern in a bucket and add ten liters of rainwater. Leave for three days and then spray undiluted onto the affected plants. Don't forget the underside of the leaf! If the infestation does not improve, repeat the process again after about two weeks.
If that doesn't help, you'll have to resort to chemical pesticides. For example, fungicides against rust fungus or a universal fungus-free are helpful. We recommend, for example, Compo Duaxo Universal mushroom-free (available here). It stops the spread of fungal diseases and protects against reinfestation.
Important:
Never plant mallows in the same place. The fungus can eventually survive in the soil and infect the new mallow plants as well. So choose a new location every year.