Because Magnolia X brooklynensis 'Yellow Bird' is a prized plant for my wife in the Drapescape, I keep a watchful eye on its performance. Unfortunately, this year the frosty weather nipped it as the butter-yellow flowers were emerging; therefore, the floral display merely rated a so-so glance, rather than the typical stunning WOW! As I was mowing around it, I got a close up, face full of leaves allowing me to note the holey havoc wreaked on its leaves.
The Swiss cheese-like magnolia leaves are the result of feeding by overwintered adults of the Yellow Poplar Weevil (YPW), Odontopus calceatus, also known as sassafras or magnolia weevils. These small, black to brownish, adult snout beetles will feed on and damage plant hosts like tulip or yellow poplar (Liriodendron tulipifera), sassafras, and magnolia.
Like any good plant diagnostoid, I couldn’t stop myself from looking for possible patterns, hole shapes and sizes in the leaves and the overall extent of damage. Some leaf holes were kidney bean-shaped, others appeared to be almost perfectly round. The holes are randomly scattered across some leaves, yet other leaves are absolutely riddled with holes. There are no discernible, consistent patterns or site placements for the holes in the leaves. Most of the larger holes were made earlier in the season as evidenced by the edges of the holes being completely healed over.
Current leaf damage appears as small, raw, open-edged, kidney bean-shaped holes, due to YPW adults feeding on mature leaves. The other evidence of YPW adults being involved in the leafmining activity, is the fact that the damage always originates somewhere along the leaf midrib.
During an outbreak of YPW on tuliptrees in Southern Ohio, BYGLer Joe Boggs noted the following, “YPW have one generation per year; however, adults feed twice during the growing season. Adults spend the winter in protected sites such as the duff beneath trees. They emerge in the spring to feed, mate, and lay eggs in leaf midribs. This is the so-called "spring generation" of adults. The "summer generation" arises from the leafmining larvae. There are typically a greater number of adults in this generation compared to the spring generation meaning that most of the damage is done in early to mid- summer. Although yellow poplar weevils are finished feeding in central Ohio, the damage will remain evident throughout the season.”
We have the evidence of our “spring generation” in NE Ohio which feed on the leaves, mate, and then lay eggs in leaf midribs. We are now moving into the “summer generation” phase, based on the recent leafmining activity noted in the leaves of my ‘Yellow Bird’ magnolia.
I have other types of magnolias scattered in the Drapescape, like Sweetbay Magnolia (Magnolia virginiana) and ‘Ann’ ‘Betty’ and ‘Jane’ of the Little Girl Magnolias. Interestingly enough, none of these smaller leafed species of magnolias, at least right now, show any evidence of YPW feeding at all!! At the current time, damage from the YPW is limited to the large leaf magnolia species that have cucumbertree (Magnolia acuminata) in their parentage.
Luckily, if these YPW are making a holey mess of your magnolia, don’t worry because no long-term damage is done by these weevils feeding on magnolia leaves. Yes, it can be worrisome to look out and see brown leafmines and the leaves full of holes—but it will all be okay. Just relax and enjoy discovering all of the intricate patterns of holes created by these insects contentedly munching the leaves of your magnolia!
