The Beetle: Everything About The Polyphagous Shot-Hole Borer

Your one-stop destination to learn about the polyphagous shot-hole borer (PSHB). Series of articles with all the information to bring you up to speed, and shorter snippets for FAQ (Frequently Asked Questions).

polyphagous shot-hole borer on a tree trunk
polyphagous shot-hole borer on a tree trunk
polyphagous shot-hole borer on a tree trunk

21 Critical Facts About the Polyphagous Shot Hole Borer

  1. Tiny but mighty: The beetle’s the size of a sesame seed—about 2–3 mm long—small enough to sneak anywhere.
  2. Shape of a troublemaker: It’s cylindrical, dark brown to black, with a shiny back and stubby legs—built for boring, not showboating.
  3. Fungal BFF: It teams up with Fusarium euwallaceae, a fungus it carries in mycangia (special body pockets)—they’re a deadly duo.
  4. Not a wood-eater: Unlike most beetles, it doesn’t munch trees—it farms the fungus inside them and eats that instead.
  5. Shot hole signature: Its tunnels leave tiny “shot holes” in bark—like BB gun pellets—easy to spot, hard to stop.
  6. Fungus does the killing: Fusarium euwallaceae clogs the tree’s xylem (water pipes) and pumps toxins into it, starving and poisoning the host.
  7. Polyphagous power: “Polyphagous” means “many-eating”—it attacks over 200 tree species, from avocados to oaks to native Virgilia.
  8. Healthy tree hunter: Unlike most ambrosia beetles, it hits thriving trees, not just dead or dying ones—game-changer status.
  9. Southeast Asian roots: Native to Vietnam, Thailand, and Malaysia, where it’s chill—local trees handle it fine.
  10. Global invader: Trade (crates, firewood) spread it to California (2003), South Africa (2017?), Israel (2009), and beyond.
  11. Fornicatus frenzy: “Fornicatus” (Latin for “fornicator”) fits—females mate with sons, sparking fast colonies from one beetle.
  12. Breeding speed: Egg to adult in 22 days at 25°C (77°F); one female can produce 57 daughters in six weeks—population explosion central.
  13. Female takeover: 10:1 female-to-male ratio—daughters fly off to new trees, males stay home, wingless and mating.
  14. Climate booster: Warming speeds breeding; droughts weaken trees, making them easy targets—thanks, climate change.
  15. Urban menace: Loves city trees—stressed from pruning and heat islands—like Johannesburg’s 10 million-strong forest.
  16. Sneaky arrival: South Africa’s 2017 “outbreak” might’ve started earlier—2012 Durban sample suggests it was undercover.
  17. Human highway: We fuelled it—shipping, firewood hauls (think braais), and lax rules let it hitch rides worldwide.
  18. Adaptable attacker: Hits native and exotic trees alike—carobs in Israel, figs in Cape Town—nothing’s off-limits.
  19. Fungal lingerer: Even after beetles leave, Fusarium euwallaceae stays, infecting stumps and waiting for more hosts.
  20. Outshines cousins: Beats redbay (laurel-only) and tea borers (tea-only) with its wide range and healthy-tree guts.
  21. Economic sting: It costs millions—$40 million in California avocados and R275 billion in potential urban tree damage in South Africa.

It is rare to identify the shot hole borer in your garden by actually seeing the beetle. Instead, the symptoms of its presence (like dying branches or sap oozing from holes in the tree trunk) are more likely to draw your attention.

HOW TO DETECT THE SHOT HOLE BORER

Article Series

Dive into the shot-hole borer’s world! We’ve cut the fluff, packed in the facts, and spun a captivating tale. New to this pest? Start at the beginning and journey through its bizarre life. You won’t believe what you’ll discover.

Frequently Asked Questions

A few snippet-like answers to frequently asked questions about the Polyphagous Shot-Hole Borer.

Is the beetle really present in South Africa?

Yes, the Polyphagous Shot Hole Borer (PSHB) is present in South Africa. It was first detected in 2017 and has since been found in several provinces, including Gauteng, KwaZulu-Natal, and the Western Cape.

Where does the beetle come from?

The Polyphagous Shot Hole Borer (PSHB) is native to Southeast Asia, specifically Vietnam and Taiwan. It has been accidentally introduced to other parts of the world, including South Africa, through international trade and human activity.

Is it easy to spot the beetle in my garden with the naked eye?

The Polyphagous Shot Hole Borer (PSHB) is a tiny beetle, approximately 2 mm in length, making it challenging to spot with the naked eye. It’s often easier to identify the symptoms of an infestation, such as tiny holes on tree trunks, branches, and stems, or staining and discoloration around the holes. A magnifying glass or hand lens can be helpful in spotting the beetle itself.

How does the beetle kill a tree?

The Polyphagous Shot Hole Borer (PSHB) kills trees by introducing a fungus, Fusarium euwallaceae, into the tree’s vascular system. The beetle creates tunnels in the tree, and the fungus grows, blocking the tree’s ability to transport water and nutrients. This leads to dieback, yellowing of leaves, and eventual tree death. The fungus also produces toxins that further damage the tree. This process can occur rapidly, often within a few months to a year.

Why is the fungi so successful in destroying trees?

The Fusarium euwllaceae fungus is a successful killer of trees because it is well adapted to its role as a pathogen. It produces toxins that disrupt the tree’s vascular system, cutting off its ability to transport water and nutrients. The fungus also grows rapidly, colonizing the tree’s tissues and producing enzymes that break down its defenses. Additionally, the fungus is protected from the tree’s immune system by the beetle’s tunnels, allowing it to grow unchecked and ultimately kill the tree.

Why is it so difficult to stop the spreading of the beetle?

The Polyphagous Shot Hole Borer (PSHB) is difficult to stop due to its tiny size, allowing it to hide in small crevices and cracks. It can also survive for weeks without food or water, making it resistant to quarantine measures. Additionally, the beetle can be transported through contaminated wood, soil, and plant material, making it easy to spread unintentionally. Its ability to infest a wide range of tree species also complicates control efforts.