New Planting of Thornless Blackberry
I planted 6 Chester thornless blackberry plants last June. They are in a sunny site, heavy clay soil that is heavily amended with commercial organic compost. All plants pretty quickly starting developing the same silvery mid-leaf spots as shown in the pictures. All the plants are doing well despite some leaf loss. Thank you in advance for any advice!
Yamhill County Oregon
Thank you for your question. I suspect it is the condition described in this handbook: https://pnwhandbooks.org/plantdisease/host-disease/blackberry-rubus-spp-septoria-leaf-spot However, a positive ID and treatment recommendation would require examination of the leaves. Are you able to take some leaf samples to your county Extension office? Although they will be closed tomorrow, you can contact them through this webpage: https://extension.oregonstate.edu/yamhill Good luck!