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The Year Of The Aphid

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The Year Of The Aphid

Jun 1, 2023
Arboriculture Horticulture Plant Health Care Local Horticulture
Honeydew on leaves
European beech (Fagus sylvatica) being inundated with aphids.

I’ve never seen honeydew raining down as it is this year in my area of southwest Ohio. The BYGL has chronicled much of this.
Honeydew on Maple Leaves

Sticky, Dripping Maples

Late last week, I came across plantings of red maples (Acer rubrum) in a commercial landscape in southwest Ohio that were dripping sticky, sugary, honeydew; the calling card of phloem-sucking insects. A close look revealed the trees were festooned with Calico Scale (Eulecanium cerasorum) and European Fruit Lecanium (Parthenolecanium corni).
Woolly Beech Leaf Aphid

Sticky, Dripping European Beech

I’m a fan of beech (Fagus spp., family Fagaceae) from American beech (F. grandifolia) to European beech (F. sylvatica) to beechwood-aged potations (F. beerlignumia). Members of the genus have long been considered relatively free of serious insect pest and disease problems. Unfortunately, beech bark disease and the enigmatic beech leaf disease are changing that perception.
Black Sooty Mold on Bur Oak Stem

Sticky, Dripping Oaks and Ghost Scales

I recently visited a commercial landscape that had 5” – 6” DBH bur oaks (Quercus macrocarpa) with their newly expanding leaves speckled with clear, sticky honeydew. Twigs and branches had a dark, dingy patina owing to black sooty molds colonizing honeydew in the past indicating the problem was not new.

In response to my inquiry, OSU’s Joe Boggs weighed in with his observations which mirrored mine:

I’m no longer parking in the shade of large trees!  Like you, I’ve never seen anything like this before.  Yes, we occasionally see outbreaks of specific aphids and soft scales, but this is across the board.

In fact, I’m calling this “The Year of the Aphid.”  As you noted, I’ve already posted an Alert about Myzocallis Oak aphids, but I visited some trees in a park in Hamilton (Ohio) this past Tuesday afternoon and the leaves were as sticky as fly paper!  That’s no exaggeration.  Also, owing to our lack of rainfall, some of the honeydew had crystallized to form white salt-like crystals on the upper leaf surface.  I’ve only seen that once before with a sap-sucking insect:  it was last year with our spotted lanternfly infestation.

Then, I walked a short distance away and came across tuliptrees that had virtually every leaf covered in honeydew from tuliptree aphids.

I believe our Year of the Aphid is the result of a convergence of weather-related conditions.  First, aphids tend to be cool-season insects; they do best in the spring and fall.  We enjoyed a marvelously cool spring with our home windows open.  Second, heavy, heavy rainfall is the enemy of aphids and will also wash away honeydew.  While we had some pretty good rainfall, until recently, driving rainfall events were a bit rare.  Finally, it takes time for the 3-Ps to catch-up (Predators, Parasites, and Pathogens).  They just haven’t done so yet.

Hopefully, as temperatures continue to be warm, things will change.

J.B.
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