George B. writes: Is there any treatment for Alpha Mosaic other than plant removal? We have had a wet cool spring and the lavender bush is about 6 years old.
Alpha mosaic is a virus which attacks all areas of the plant. It is often difficult to diagnose b/c the symptoms can appear AND fade away very quickly. It is transmitted most often by certain kinds of aphids, and through the air from other infected plants.
Unfortunately, I would recommend that you dig up the plant and burn it. Please DO NOT place it in your compost pile or in the city/county yard waste bin (if you have one of those). The disease transmits easily and your best bet at containing the infection in your own garden is to burn the uprooted plant. If there were any seedlings from this plant, you may want to dig those up as well, as seeds are a path of disease transmission.
The only thing that makes me wonder about your question though, is your mention of a cool, wet spring. Alpha mosaic grows and spreads more quickly with the addition of light and heat. That isn’t to say plants can’t get this disease with cool, wet weather. They certainly can.
But because the disease is so hard to control (to my knowledge, no pesticides or insecticides can help), my recommendation is to get rid of the plant if you suspect alpha mosaic. I am sorry, it’s painful to lose a plant you have enjoyed for several years.