Spittlebug on Walnut and Frothy Thinking

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I posted a BYGL Alert! about spittlebugs on hackberry ("Odd Spittlebug on Hackberry") yesterday.  I could have added another odd spittlebug to the post - and solved an old misconception - had I waited until later in the day to write the report.  Yesterday afternoon I came across the tell-tale frothy masses of a spittlebug on black walnut (Juglans nigra) while hiking around Miami Whitewater Forest - Great Parks of Hamilton County.  The spittle-masses were located on the twigs and in the leaf axils.  Oddly, the consistency of the froth was much like the spittle-masses produced by the hackberry spittlebug:  it was very sticky and highly viscous.

 

Alder Spittlebug on Black Walnut

 

As I noted in the Alert, the spittlebug on hackberry appears to be an undescribed species belonging to the family Clastopteridae; possibly in the genus Clastoptera.  However, this spittlebug appears to be specific to hackberry.  After doing some web sleuthing, I found the alder spittlebug (C. obtusa) may be found on its namesake host as well as black walnut and occasionally on pecans (Carya illinoinensis).  The alder spittlebug also belongs to the family Clastopteridae.  Most of our more common spittlebugs belong to the family Cercopidae.

 

Alder Spittlebug on Black Walnut

 

Alder Spittlebug on Black Walnut

 

The Plot Thickens:

In 2010, I made a site visit to look at a spittlebug infestation on a pecan (Carya illinoinensis) tree and an English walnut (J. regia) tree.  The trees were planted side-by-side in southwest Ohio and were around 8" DBH (diameter at breast height); both appeared healthy.  The spittlebug "froth" was unusual in being sticky and highly viscous; I had never seen this before.  I'm not very familiar with pecan tree pests, but I found there is a pecan spittlebug (C. achatina) and its spittle-froth is described as being sticky and highly viscous.  Of course, I leapt to the conclusion that this was the spittlebug infesting both trees; after all, pecans and walnuts belong to the same plant family, Juglandaceae.  I believed this to be true until my spittle-sleuthing today revealed otherwise.

 

Alder Spittlebug on Pecan

 

Alder Spittlebug on English Walnut

 

Had I focused on the English walnut rather than the pecan six years ago, I would have discovered that the pecan spittlebug does not infest walnuts; only the alder spittlebug infests both trees.  The lesson learned is that while host range may help guide insect pest identification, you must avoid frothy thinking causing you to leap to an inaccurate conclusion.