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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.

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

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Tuesday - June 18, 2013

From: Ethel , LA
Region: Southeast
Topic: Non-Natives, Diseases and Disorders, Pests, Shrubs
Title: Waxy deposits on Magnolia fuscata from Ethel LA
Answered by: Barbara Medford

QUESTION:

I have a 4yr old Magnolia Fascata (aka banana shrub)- I noticed that it has small oval shaped yellow waxy deposits on the branches.. I have also noticed small black ants on the branches. The unknown deposits do not seem to be affecting plant growth, but just wondering what it is so that I can treat it. Thank you for the response.

ANSWER:

Magnolia fuscata or Magnolia figo (Banana Shrub) is a low evergreen tree native to China.

Banana shrub grows best in an acidic, deep sandy loam soil.  It is basically pest free but can occasionally suffer freeze damage especially in or near zone 7. From PlantAnswers.co, here is some information on Michelia figo, which is a synonym for the same plant. According to the USDA, this plant is only recorded as growing in one county in Mississippi, but obviously you are growing it in Louisiana. From Floridata, more information on Michelia figo.

Since this plant is not native to North America, we have no information on it in our Native Plant Database. However, it sounds very much to us like you have aphids on your plant, which in turn attract the ants. The ants are harvestiing the "honeydew" (aphid poop) which they feed to their young. This is the waxy substance you see on the leaves. It can turn dark with mildew. The article on aphids we referred you to above is from the University of California Integrated Pest Management and has some information on controlling it.

 

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