Monday, June 28, 2021

Pitch-mass borers serve as reminder to procrastinate

In my line of work the list of boring topics is endless. There’s the emerald ash borer, lethal but oh-so aesthetically pleasing with its metallic-flake green paint job and subtle copper highlights. A handful of powder-post beetle species love to tunnel into floor joists and dead trees to mine talcum powder, leaving behind a field of microscopic holes perfect for anyone who has a sewing needle collection they need to organize. On the other end of the spectrum are fearsome Asian longhorned beetles that chew galleries in tree trunks faster than a Black & Decker cordless drill, leaving tunnels big enough to hide a Mini Cooper.

A lesser-known member of the club is the pitch-mass borer (Synanthedon pini). It’s a native clear-wing moth which takes to the air during July to sniff out fresh wounds on pine and spruce on which to lay eggs. The larvae, which likely have many genes in common with NASCAR drivers, travel round and round the edges of the wound for two to three years. Unlike racecar drivers, eventually the borers get bored with going in circles, or maybe just dizzy. They pause to pupate, emerging to their new career in aviation.

An obvious drawback to pitch-mass borers is the unsightly mass of pitch they cause the tree to produce. These prodigious blobs of resin, which persist for many years afterward, are infused with sawdust and three years’ worth of caterpillar crap, a mixture known as frass in polite circles. Even if a predator was foolish enough to brave the hazards of one of these tar pits in search of a meal, the accretion of excretion adds another layer of deterrent.

It’s the same strategy used by lily-leaf beetle larvae, soft-bodied maggots which would be helpless if not for a peculiar grooming ritual – they slather their poop across their backsides each day like some gross hair gel. In the same vein there are humans who surround their homes with garbage and pit-bull excrement, presumably to dissuade predators, not to mention solicitors.

But the greater problem is that pitch-mass borers don’t just race around the same track. As they feed on cambium tissue and sapwood, they enlarge the wound considerably after a couple of years. The vascular system is disrupted in the area of this damage, and the tree also is vulnerable to decay organisms. Because pitch-mass borer activity leads to a reduction in wood quality, they are a concern for commercial foresters as well as for homeowners.

Rarely does a forest pest have one elegant and simple solution. Every lawn problem known to humankind can be solved by mowing at four inches high, but fixing the emerald ash borer, spotted lanternfly, or Asian longhorned beetle problem has all but stumped the best minds in science.

Managing pitch-mass borers, however, is as easy as falling off a log. Easier, actually, because there is no risk of injury. If you’re tempted to prune your pine or spruce this summer, wait until winter. It’s hot out anyway. By the time pitch-mass borer adults are active in July, the wound will have dried out for several months and will no longer be attractive as an egg-laying site.

Voilà – another problem solved through procrastination. It’s one of my favorite strategies, although sometimes it can get boring.

Paul Hetzler has been an ISA-Certified Arborist since 1996, and a procrastinator for even longer.

Image courtesy of Wikimedia Commons user Ryan Hodnett

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Paul Hetzler has been an ISA Certified Arborist since 1996. His work has appeared in the medical journal The Lancet, as well as Highlights for Children Magazine.You can read more of his work at or by picking up a copy of his book Shady Characters: Plant Vampires, Caterpillar Soup, Leprechaun Trees and Other Hilarities of the Natural World

4 Responses

  1. Bill Ott says:

    I have fallen asleep reading this boring article so many times that I have procrastinated my reply. Keep up the good work Mr. Hetzler. I sleep much better now.

    • jack rikess says:

      Mr. Ott,

      You really went out of your way to disparage Mr. Hetzler’s article.Is it that prefer an ISA’s take on bugs, maybe something less personal and more academic? When you go out for ice cream, be thankful that vanilla ice cream will always be stocked for people like you. I know all those varieties must throw you. We live in the Time of Trolls. Especially when a writer attempts something different. But as your comment stated, you’re sleeping much better now. Because that’s what is important; how Life affects you.

      • Bill Ott says:

        I was trying to be light hearted, not disparaging, but apparently failed. I always enjoy Mr. Hetzler’s articles, and I respect your comment 100%.

  2. Sam says:

    Thank you for this informative post. What do we do if the wounds are on the trunk of the tree? Please advise.