Magnolia weevils causing a stir in gardens

This past Tuesday I saw something that I have not seen before on our magnolias, specifically the cultivar “Yellow Butterfly.” The new growth looked pretty ragged and had lots of brown spots all over it.

After looking a little closer, I found a tiny black weevil; the culprit is the magnolia weevil, one that I haven’t seen before in this area. It’s also known as the yellow poplar or sassafras weevil and damages these plants, as well.

My colleagues in the northeast part of the state have talked about his pest before and its damage to magnolias for several years now. This is the first year that I have seen it in the Miami Valley.

This weevil is tiny enough that some are mistaking it for a tick. Close inspection of the head reveals the normal weevil snout. In addition, ticks don’t fly, and these insects do.

Apparently there is a large outbreak of magnolia weevil in central Ohio that is causing quite a stir for my entomologist friends. They are getting calls about droves of “flying ticks.” Some places in the Columbus area are seeing great bunches of them on golf courses and swimming pool decks.

The adult weevils have emerged and are feeding on the underside of the leaf, causing the brown spots to appear. Eventually these spots will die and the leaf tissue will drop, leaving a hole in the leaf.

They will feed until late June and July and then drop to the ground. The adults begin to feed again in April and May on the buds of the magnolia. When they open, the leaves have tiny moonlike holes in them.

They lay their eggs and then the grublike larvae feed in between the leaf surfaces or feeding as leaf miners. This portion of the leaf eventually turns brown, and the leaf falls off.

Damage to trees is unsightly but rarely kills a tree. You might see some defoliation, but for the most part, the damage is cosmetic.

However, damage might be more severe under drought or drought-like conditions so we might see considerable damage this year.

The University of Kentucky entomologists recommend treating when damage occurs on leaves on more than 10 percent of the branches.

Insecticides containing carbaryl will do the job, but may need to be reapplied as the weevils have an extended feeding period.

I would keep an eye on smaller trees and either handpick off small populations of weevils or treat to prevent major defoliation.

At this point in our garden, we won’t spray and will observe the situation.

For more details on this pest, visit http://go.osu.edu/magnoliaweevil for the University of Kentucky fact sheet on yellow poplar weevil.

Pam Corle-Bennett is an Ohio State University Extension horticulture educator and the state Master Gardener volunteer coordinator.

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