photo from bioseaoz.com.au
With all the rain we’ve had in recent weeks here in Austin, I’ve noticed an increase in some plant diseases, specifically powdery mildew. This nasty problem is nothing to mess around with, as it can spread and destroy your plants. Eeek! Let’s do something quick! Here’s the lowdown:
What: It’s a super gross, talcum-powder like growth occurring usually on the top sides of leaves.
Why: Despite popular thought, powdery mildew does not develop because of water on plant leaves. Water doesn’t help, but the real culprit is humidity of 90% or more. That and crowded plants in shady areas that don’t get enough air circulation.
Where: We see it more in hot climates, and on new tender growth.
Who: Well, plants aren’t a “who,” but what the heck, I’m going with a theme here. Plants that are susceptible include roses, coneflowers, rock rose (that’s where I’ve seen it this week), viburnums, crape myrtles. Check this site out for a more complete list.
Now, what to do. It’s not rocket science (or “rocket surgery” as I once said during a Blonde Moment):
- Remove and destroy all infected plant material.
- Do not compost this crap!
- Selectively prune susceptible plants in shady areas to increase air circulation.
- Avoid overhead watering in areas of susceptibility.
- Avoid late summer applications of nitrogen fertilizer.
- Treat with a fungicide: sulfur, neem oil (Rose Defense), triforine (Ortho Funginex) or potassium bicarbonate (First Step)
And that’s all she wrote. Once you understand what this is and why it happens, it’s a problem that is pretty easily intuitively solved. Unless you’re having a Blonde Moment–and it’s okay, we all get them– in which case I recommend you just take a deep breath and wait for the moment to pass. Then channel your Inner Brunette and deal. Your rock rose will thank you!
{ 3 comments… read them below or add one }
I just watered with seaweed and fish emulsion last week at one of the gardens I maintain. This morning I went by to check it as usual and found powdery mildew all over my butternut squash plant. Do you think its worth it to remove most of the leaves? I’ve heard if you spray it with baking soda or milky water you can get rid of the mildew. Have you ever tried any of that?
Thanks.
Liz
Hi Liz! No, I haven’t heard of baking soda or milky water; I’ll look that up tomorrow! I do think you should remove the leaves, because it can spread to surrounding plants. I’ll let you know what additional information I uncover!
Thanks. I’m interested to know. I’m going back to that garden Tuesday to try to battle the problem.