powdery mildew on lupine

Asked October 16, 2019, 10:51 PM EDT

My potted lupine plants have powdery mildew and I'm getting rid of the plant. Do I also need to dispose of the soil? What about lupine in the ground, do I need to dispose of the plant and/or the soil?

Linn County Oregon

1 Response

Thank you for your question. Powdery mildew is one of several plant-specific fungi which overwinter on plant tissue. Removing all of the infected tissue and disposing of it (do not compost) should remove the fungus from the area, without having to remove the soil. Before replanting there, you can place black plastic over the soil to ‘solarize’ it, raising the temperature to kill the fungus on any residual tissue. Replanting with a fungus-resistant variety, or a different species of plant, can obviate that problem. However, since the spores of all of these fungi are spread by wind, it is impossible to keep them off of the plant. Here is more information on the topic: https://pnwhandbooks.org/plantdisease/host-disease/lupine-lupinus-spp-powdery-mildew Good luck!