En EspaŅol

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.

Help us grow by giving to the Plant Database Fund or by becoming a member

Did you know you can access the Native Plant Information Network with your web-enabled smartphone?

Share

Ask Mr. Smarty Plants

Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.

Search Smarty Plants
    
 
See a list of all Smarty Plants questions
Can't find the answer in our existing FAQs, submit a question to Mr. Smarty Plants.
Need help with plant identification, visit the plant identification page.
 
rate this answer
Not Yet Rated

Tuesday - September 02, 2008

From: San Diego, CA
Region: California
Topic: Diseases and Disorders
Title: Mildew and rot in navel orange tree in California
Answered by: Barbara Medford

QUESTION:

I have a great navel orange tree that seems to have two problems. One of them looks like powdery mildew and the other is some kind of black rot. I have sprayed it several times to no avail. I live near the ocean in San Diego. Any suggestions?

ANSWER:

Citrus sinensis is a hybrid of ancient origin from Southeast Asia. At the Lady Bird Johnson Wildflower Center, we are focused on plants native to North America. However, we will see if we can find a resource for you to check and see if you can find a way to take care of your tree.

We found an excellent site on dealing with problems with the navel orange trees. We really tried to find one from California but couldn't, so you'll have to accept this Texas Cooperative Extension site, instead. Then, if you're dedicated to finding a solution, go to this site, "Diagnosing common citrus problems", and see what you can find that fits your situation.

As in a great many plant problems, especially, it would seem, with trees, plant stress gets a lot of the blame. One reference said that orange trees should be fertilized 6 times a year, starting in early March through August/September. Maybe your tree is just hungry. Or, if the trunk is not above the surface of the surrounding garden, or there is mulch spread over the root zone, the tree may be developing root rot or foot rot. Charming terminology. It look to us like the experts were pretty nonchalant about most of the problems with navel oranges, with comments like "not worth treating", etc. It's up to you to plow through that chart on citrus problems and see if it's worth it to you.

 

More Diseases and Disorders Questions

Need to identify a fungus in a flower garden in Lansinging, MI.
April 25, 2012 - I have a fungus in my flower garden. It is white and ground hugging. It is in a moist area under a large spruce where mulch has been laid down. When I step on it , it expels a green dust. What is it a...
view the full question and answer

Care for heritage roses
October 07, 2007 - Dear Mr. SmartyPlants, I took some cuttings from an antique rose my grandmother had.I had good luck , had some of them grow for me. Some of them have blooms and others are long and lanky stems but n...
view the full question and answer

Black Sooty Mold on Bay Tree
February 25, 2013 - I have a large bay tree and all the leaves are covered with a black mold-like substance on the top part of the leaf. Under each leaf are some black/brown spots. I have washed the leaves with soap and ...
view the full question and answer

Why is my recently planted Esperanza doing poorly in Texas City, TX?
May 28, 2010 - I have an Esperanza I planted about 2 months ago. It has been doing well, except today all but one stem of the plant is wilting and the leaves are rolling. I see no bugs on the plant. Any idea what...
view the full question and answer

Muhly grass slow to green up from Spring Hill FL
August 04, 2012 - Have lots of muhly grass planted 3 yrs ago. This yr about 1/3 are VERY slow. Still look like hay stacks. No pattern in the bed. You mentioned pesticides being too close?
view the full question and answer

Smarty Plants's Facebook profile Support the Wildflower Center by Donating Online or Becoming a Member today.

Mr. Smarty Plants wants you to be his Facebook friend. Click the Facebook icon to add yourself to Mr. Smarty Plants list of friends.
E-NEWSLETTER | BECOME A MEMBER | DONATE NOW | MEDIA | SITEMAP | STAFF
© 2015 Lady Bird Johnson Wildflower Center