Black Mold With Flies on a Magnolia Tree

Magnolia scales can measure up to 1/2 inch in length.

The native magnolia scale (Neolecanium cornuparvum) uses its powerful mouth to suck the nutrients from a magnolia tree. The insects secrete a honeydew like substance that grows unsightly black mold. The sweet substance attracts flies, bees, ants and wasps.

Appearance

Magnolia scales can completely cover the branches of the magnolia tree. The insects cover their bodies in an immobile waxy purple substance. From June to July, the waxy covering takes on a white coloration and the insects begin to secrete honeydew, which attracts a profuse amount of insects. The honeydew that the insects secrete drips onto the foliage and branches of the tree in abundance and quickly grows black mold.

Life Cycle

The female scales give birth to live young crawlers. The young crawlers attach their mouths to the tree to suck its nutrients and begin to form a protective scale covering. They will overwinter on the tree's branches beneath their protective scale.

Control

In the fall and spring consider applying horticultural oils to gain control over the insects. Using insecticidal soaps in late August and September can control the newly born crawlers. Once the crawlers have formed a protective shell and gone dormant for the winter, sprays and oils are ineffective.

References

• Penn State College of Agricultural Science: Magnolia Scale Fact Sheet
• Ohio State University Extension: Magnolia Scale And Its Control
• University of Illinois: Magnolia Scale
• Rhode Island University: Scale Insects
• Cornell University: Magnolia Scale

Resources

• The Morton Arboretum: Magnolia Scale