Native Plants
Q. Who is Mr. Smarty Plants?
A: There are those who suspect Wildflower Center volunteers are the culpable and capable culprits. Yet, others think staff members play some, albeit small, role. You can torture us with your plant questions, but we will never reveal the Green Guru's secret identity.
Did you know you can access the Native Plant Information Network with your web-enabled smartphone?
Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.
rate this answer
Friday - May 30, 2014
From: Morrisville, PA
Region: Mid-Atlantic
Topic: Diseases and Disorders, Herbs/Forbs
Title: Mildew on phlox paniculata from Morrisville PA
Answered by: Barbara Medford
QUESTION:
My Phlox paniculata, all 7, have powdery mildew. I read about using NEEM to combat the mildew. NEEM is organic but the bottle says it is also an insecticide. The phlox are near my milkweed and goldenrod, I want to be careful what I use. Can the Phlox be saved?ANSWER:
Please follow this plant link, Phlox paniculata (Fall phlox), to our webpage on the plant and see if the growing conditions in your garden match those of this plant. From that page, we extracted this: "Conditions Comments: The plant needs at least 6 hrs. of sun per day. Powdery mildew is a frequent problem."
Next, please read this article from Colorado State University Extension Powdery Mildew. From that source, we want to emphasize this paragraph:
"Conditions That Favor the Disease
The severity of the disease depends on many factors: variety of the host plant, age and condition of the plant, and weather conditions during the growing season."
Powdery mildews are severe in warm, dry climates. This is because the fungus does not need the presence of water on the leaf surface for infection to occur. However, the relative humidity of the air does need to be high for spore germination. Therefore, the disease is common in crowded plantings where air circulation is poor and in damp, shaded areas. Incidence of infection increases as relative humidity rises to 90 percent, but it does not occur when leaf surfaces are wet (e.g., in a rain shower). Young, succulent growth usually is more susceptible than older plant tissues."
Scroll down that page to the area on "Control," which includes some suggestions on chemical controls.
Those of us who live in blazing, drought-stricken Texas don't tend to think of Pennysylvania as "warm, dry," but everything is relative, and we believe the growing season for your phlox probably is warm and dry. However, as noted above, if you don't have 6 hours or more of sunshine directly on the plant it is probably going to be very mildew prone. Possibly when you first planted your phlox, shrubs and trees around it were small, and the phlox was not very thick. You can certainly try thinning out the phlox, possibly even some pruning of overhanging woody branches, but NOT IN VERY HOT WEATHER!
From the Image Gallery
More Diseases and Disorders Questions
Death of Texas Betony and Blackfoot Daisy from Austin
April 18, 2013 - I have one small area that there are two plants - Texas Betony and Blackfoot Daisy withered and died eventually. Same kinds of plants are doing fine close by. It is my front yard close to walk way.I w...
view the full question and answer
Problems with a Sherman (Shumard?) Oak from Bixby OK
May 14, 2012 - We have done extensive research on oak fungi/diseases/pests could be affecting our Sherman Oak tree but we are stumped. The leaves are falling off and have some sort of moldy bunch within the leaf it...
view the full question and answer
Tilling for grass under old live oak in San Antonio
April 15, 2012 - Hi,
I have a 250+ year old Texas Live Oak. As usual, the lawn under the tree, after 18 years needs to be redone. MY QUESTION: to put down new sod the lawn company needs to till the soil about 4 t...
view the full question and answer
Leafing out problems with oaks in Towson MD
June 02, 2012 - 3 native 5-year-old oaks kept old leaves until March and are not leafing by the end of May. The few leaves that have emerged are shriveled. WHAT'S WRONG?
view the full question and answer
Pin Oak Dropping Leaves Early
December 17, 2015 - I have a large pin oak that's losing it's leaves at this time. Is this too early? I have been watering the tree during the hot, dry weather and overall the tree looks healthy and has a good crop of ...
view the full question and answer
Support the Wildflower Center by Donating Online or Becoming a Member today. |