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Tree Care Tips

Why Are There Wasps on My Magnolia?

Learn more about magnolia scale

Once your magnolia is past its spring bloom, you may notice something else on your tree: Why are you seeing wasps on magnolias? Wasps on your tree may look benign, but they can indicate a bigger problem called magnolia scale.

This disease affects magnolia trees and is at its peak in Ontario in July. To keep your magnolia healthy, magnolia scale needs treatment. Unfortunately, magnolia scale is a multi-part, multi-insect problem!

What is magnolia scale?

Magnolia scale is caused by a different insect, magnolia scale insects. These bugs drink the magnolia tree’s sap, then excrete it as a substance called honeydew. It’s similar to the problem of aphid honeydew.

The honeydew ends up coating the tree, dripping, and sticking to everything below. After the tree is coated in honeydew, a black fungus — sooty mould — can grow on the honeydew.

Scale insects are part of a group of insects called soft scale insects that feed on sugar and water from trees. Magnolia scale insects are one of the larger types in this family and can be pinkish-orange or brown in colour.

The sooty mould can cause problems by blocking light to the tree. Leaves or branches can die or weaken when they can’t get enough sunlight.

Why are wasps attracted to magnolia trees?

White and purple blossoms on magnolia tree in spring

So why are you seeing wasps on magnolias with magnolia scale? Since it’s made of sap, the honeydew is a sweet, sticky syrup that attracts bees and wasps. Honeydew is a food source for bees and wasps, so it’s not all bad if you’re looking to attract pollinators to your garden. However, most people are wary of swarms of wasps in their yard.

Some years are worse than others for magnolia scale infestations in Ontario. They typically hit their peak in July.

How do I identify magnolia scale?

Wasps on magnolias, or bees, can be one sign you’re dealing with a magnolia scale infestation. Sticky residue from the honeydew on or around your magnolia is also a sign. If the residue has led to sooty mould developing on the tree’s leaves, or on areas close to your magnolia tree, like a patio, it’s a sign the infection needs treatment. You may also notice bumpy, waxy white nodes on your tree’s branches.

How do I get rid of wasps on my magnolia tree?

To get rid of wasps, you’ll need to treat the magnolia scale infestation. Unfortunately, this can be a two-season process to fully eliminate the infestation.

An arborist can treat magnolia scale with a multi-step spraying process. If the infestation is limited to a couple of branches, it may be possible to simply prune those branches off. 

The best time of year to treat magnolia scale is in September or October. That’s when scale insect eggs hatch, and insecticides, or insecticidal soap, can be sprayed on the tree to control the scale population. It’s also possible to spray the tree in early spring, when there’s a narrow window before it buds. This is particularly good for prevention if your tree was treated for magnolia scale during the previous summer and fall.

If you’re looking to help stop the infestation now in summer, you may be able to remove scale insects manually. However, they can be very tough to get off. 

You can remove honeydew by spraying the tree with a hose. This may knock off some insects and nodes, but they are tricky! Always use a hose, never a pressure washer — it’s too strong for a magnolia’s bark. In July, the insects don’t have legs, so they can’t get back into the tree if you knock them off. Be careful if you find yourself spraying leaves right off your tree.

Effective magnolia scale treatment

For the best treatment, an arborist or pest control professional can help you manage a magnolia scale infection. We can assess the scope of the issue and provide pest treatment as needed. We’ll return for multiple visits over the year to ensure the magnolia scale is gone.

Magnolias are beautiful Ontario trees many homeowners and neighbours delight in each spring. Don’t let a magnolia scale infection bring yours down — request an estimate from Vista Tree to treat your magnolia!

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