Oh no! Rust virus attacks the Lavatera shrub!
Well, the rust disease is attacking our lavatera shrub and this is not going to be a cheerful post.
Lavatera is member of the mallow family, which includes abutilon and hollyhocks. All of these plants are prone to rust, a fungal disease which is spread by spores in the air.
As you can see in the photo above, bees are still happily visiting and collecting pollen from the blossoms, which look healthy. But you can also see the pustules on the undersides of the leaves behind the blossom.
Even the ladybugs can't possibly save the shrub!
The pustules multiply on the undersides of the leaves, the leaves turn yellow and drop off. AND this disease can spread to other mallow plants in your and your neighbors' garden.
Unfortunately the Bay Area weather provides optimum conditions for the disease: 4 to 8 hours of high humidity, such as fog or heavy dew, followed by at least 8 hours of high light intensity and temperatures and/or slow drying of the leaf surface.
This disease attacked the same lavatera shrub 4 or 5 years ago (pre-drought).
After doing some research, I learned what this affliction was, and how to deal with it.
Basically, we had to cut down the entire shrub, down to its trunk and shortened the main limbs of it, leaving absolutely no vegetation. Then we covered the soil all around the shrub, with mulch, about 2 cubic feet worth of it, at least 2 inches deep. We didn't water the mulch at all.
Within a couple of months the shrub was growing again, producing healthy leaves. Lavatera is a fast growing plant, and is hardy. I just feel very badly for the bees, birds and butterflies that frequently visit the shrub, which is currently about 8 feet wide and 8 feet tall.
Fortunately we do currently have other plants that provide food and shelter for these creatures in the garden, among them, lavender, many kinds of salvia, borage, and nasturtiums.