Knowledgebase
Large/ Prolific Pitch Masses on Ponderosa Pines #855437
Asked November 17, 2023, 10:46 AM EST
The HOA I live in (Littleton CO area) has a large amount of Ponderosa Pines, and this season I noticed that on nearly every one (over 100 trees), large masses of pitch have formed. Many of these masses have pupal casings sticking out. I am curious if there is an obvious ID for this insect. All pines are generally in good health based on canopy condition. They are planted in turf with generally ample water supply.
I am familiar with the Pinyon Pitch Mass Borer (Dioryctria ponderosae) that can also utilize ponderosa pines as a host, but I do not believe that they leave obvious pupal casings sticking out of the pitch masses. My best guess is some sort of clearwing moth species, as I know many members of the family sesiidae leave behind the pupal casting in this manner.
Nearly every tree had upwards of 7-8 large pitch masses on the main trunk in the lower 20-30 feet, as well as a few on larger scaffold branches. This was widespread throughout the area.
Jefferson County Colorado
Expert Response
Hello,
Based on your description and what I can see, I suspect that it is a member of genus Dioryctria, including possibly D. ponderosae (the pinyon pitch borer), D. tumicollela , or possibly even D. zimmermani, the Zimmerman pine moth. Zimmerman pine moth is known to have the pupal skins stuck like this; it's possible that the other members of the genus also show up looking like clearwing borers, too.
All three of those Dioryctria are known to attack the trunks of ponderosa pines at the heights you describe.
I hope this is helpful.
Cordially,
John
John,
Thank you for your reply. Interesting that the Dioryctria species also leave their pupal casings sticking out of the exit hole! Must be a challenging start to adulthood having to wriggle out of that sticky mess.
Is it typical for D. zimmermani, or any of the Dioryctria species for that matter, to attack areas in the middle of the trees bole? I had always thought they mostly targeted branch-bole intersections, and smaller diameter wood too. I would say that 90% of the pitch masses were on "internodal" wood, and most of these trees were > 15" diameter.
The scope of the "infestation" was striking given how seemingly healthy all these trees are. Quite literally hundreds of ponderosa pines with prolific pitch masses on each tree. Do you have any resources on Dioryctria that you could point me to? I would love to do a deep dive on this genus, simply for my own learning! Thanks again.
- Ryan Clemo
Hi Ryan,
Sorry for the delay, I was out of the office last week.
I think you're right that branch unions near the top of the tree are most common for Zimmerman pine moth, but the other genera seem to be more likely to be found at mid-height and not necessarily associated with branches from what I can tell in the literature I've found.
You might like this thesis on the pest members of the genus found in Nebraska: https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1235&context=natresdiss
I hope this helps!
John
