(News article for March 2020)
Banana shrubs, also known as magnolia fuscata, are a wonderful addition to Louisiana landscapes. They provide evergreen color and a lovely banana fragrance in the spring. There is no mistaking one, once you’ve smelled it!
Each spring I receive several inquiries about banana shrubs looking shabby. The trees start blooming around late February through March, which is when most people start paying more attention to them. Most evergreen trees and shrubs shed old leaves in the spring, therefore it is completely normal to see a few yellowing leaves and some leaf shedding.
Scale insects will also cause a banana shrub to look shabby, but most people don’t notice them until they have a large infestation. Scale insects have piercing-sucking mouth parts and feed on the sugary sap of the plant. Once they have settled on a spot, they dig in and cover themselves with a waxy substance, making it hard for insecticides to kill them.
The first sign of a scale infestation is sooty mold. Most sucking insects secrete a sugary substance called honeydew. Honeydew will build up on the leaves, causing them to look shiny and sticky. Next, the honeydew will grow a black fungus called sooty mold. It looks just like it sounds, like soot all over your plant! Other sucking insects such as aphids also cause sooty mold, therefore it is important to identify the insect before treating.
Another sign of scale insects are yellow spots on the leaves of your plant. Remember, the scales are sucking the juices from your plant. Wherever they eat you will see yellow or brown spots.
Lastly, you may see the scales themselves. There are multiple types and colors of scales but the scales I see most often on banana shrubs are white. You may see white dots on the leaves or stems. Tea scales like to hide out underneath the leaves, so don’t forget to check there as well.
Thankfully, scale insects do not normally kill a plant, they only cause it to look ugly for a time. If you have scales, the best way to treat them is with a light horticultural oil found at your local garden center or co-op. Mix the horticultural oil according to the label directions and apply all over the plant, including underneath the leaves.You may need to make multiple applications to eliminate the scale.
Once the scale is under control you will have to live with the spots they have created until your plant eventually sheds those leaves.
Jessie Hoover is a County Agent with the LSU AgCenter covering horticulture in East Feliciana, West Feliciana, St. Helena, and Tangipahoa parishes. For more information on these or related topics contact Jessie at 225-683-3101 or visit the LSU AgCenter Website.
Banana shrub showing symptoms of scale infestation.
Notice the yellow spots on the top of this leaf: symptoms of tea scale.
Here you can see the tea scale underneath the same leaf.