Garden Fail: Scale

Our purple tulip Magnolia has scale, an infestation as repulsive as it sounds. It’s equally harmful and can ultimately kill the tree if left unchecked. We’ve been researching organic solutions, preferring beneficial insects if possible.

From the reading I’ve done, the scale may have been present months ago.  Beautiful blossoms covered the Magnolia last spring, with no signs of the scale.  In late June, however, I noticed some damage to of the leaves of the inner tree and only then did I discover the scale.  We have all the tell-tale signs, now that I know what to look for:

  • Crusty bumps along the branches
  • Sticky leaves caused by scale excretions
  • Ants on the leaves.  They eat the sweet excretions and are known to defend the scale since they provide a food source.

Here are a few more details from the College of Agriculture Sciences at Penn State:

Magnolia scales are usually massed on the undersides of 1 and 2-year-old twigs, with heavy infestations completely encrusting branches. Other indicators of a scale infestation include reduced foliage and flower production, undersized leaves and twigs, and a black sooty mold on the foliage. After digesting the plant fluid, the scale excretes a clear sticky liquid called honeydew, which provides an ideal substrate for the black sooty mold fungus to develop. Magnolia scale infestations often go unnoticed until the leaves and twigs of the host plant turn black with sooty mold. The honeydew also provides a food source, attracting ants, bees, wasps and flies.

Healthy Magnolia Branch

Healthy Magnolia Branch

Scale Infestation on Magnolia Branch

Scale Infestation on Magnolia Branch

Ants eat the excreted Honeydew

Ants Eating the Excreted Honeydew

The more I read, the more discouraged I become. Even the less organic solutions are often ineffective.  I read an extensive article saying that Predatory Beetles worked well, only to learn they are no longer commercially available.  Aphytis melinus is another possibility, and probably our next, best option. Pruning away the worst of the branches seems like a good idea, too.  I would hate to have this spread to our larger magnolia just a few feet away.

Suggestions welcome!

20 thoughts on “Garden Fail: Scale

  1. Oh no, that is a conundrum and nasty looking too. Ants seem to be taking over. We’ve even seen them at New House Builds this year. The odd ones find their way on to our front stoop. I give them the heave-ho with my trusty broom but you turn around and there’s five of his cousins right behind you, I could stand there and sweep all day. What do you do for ants Alys?


    • I’m not surprised to hear you are seeing them at New House Builds. I think the nests are disturbed from all the digging, so they come up and try to relocate. If you have several over and over again, it probably means you have a nest near by. Look for tell-tale signs of little piles of fine earth. White vinegar is a good, organic deterrent for ants. It’s also inexpensive, especially when you by it in large jugs.


  2. Sorry to hear you have these pests! We have scale insects on an Acer tree which we noticed when my husband rescued it from a pot it had outgrown and planted it in the garden. Sorry if this is too gross but I scraped a lot of them off with my thumb nail and then back of a small knife when my fingers got too sticky…yuk! They are still present though in not so great a number. The large red Acer also has some but not many and it doesnt seem to affect the tree at all. I’m off to check out two magnolias in the front garden!


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  4. Pingback: Magnolia Scale: It’s Not For Wimps | gardeningnirvana

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