Invasive Shot Hole Borer (ISHB)/Polyphagous Shot Hole Borer (PSHB)/ Kuroshio Shot Hole Borer (KSHB)

APC has recently found and received positive identification of Polyphagous Shot Hole Borer (PSHB)/ Kuroshio Shot Hole Borer (KSHB) in San Diego County.

Polyphagous Shot Hole Borer (PSHB) and Kuroshio Shot Hole Borer (KSHB) are new invasive beetles in Southern California that vector a disease called Fusarium Dieback (FD). The disease stops the flow of water and nutrients in over 137 susceptible tree species which can lead to the death of individual branches or, in severe cases, the entire tree.


Polyphagous Shot Hole Borer (PSHB) and Kuroshio Shot Hole Borer (KSHB) are genetically different invasive species, but morphologically they are indistinguishable.

Pregnant females bore through the tree’s bark, creating galleries under the bark. They plant the fungus in these galleries, where it grows and spreads throughout a susceptible tree. The female then lays her eggs in these galleries and when the eggs hatch, the larvae eat the fungus.

In ideal environments, larvae develop into adults in about a month. Pregnant females pick up some of the fungus in their mouths, and leave through the entry holes created by their mothers to start the process again.

Populations are currently established in Los Angeles, Orange, and Riverside Counties, and are now expanding their range into San Diego County.

Infestation Symptoms and Damage Signs:

  • Symptoms of PSHB / KSHB attacks and fungus infection differ among tree species.
  • The beetle produces a very precise, perfectly round, tiny (< 0.1 inches in diameter) entry hole in most trees.
  • Staining, sugary exudate (also called a sugar volcano), gumming, and frass (saw dust) may be noticeable before the tiny beetles are found.
  • High attack densities can lead to severe crown and branch dieback, basal sprouting, and eventual tree death.
  • Once a tree shows presence of infestation, tree survival is not certain.


What trees are Affected:

  1. Box Elder
  2. Big Leaf Maple
  3. Evergreen Maple
  4. Trident Maple
  5. Japanese Maple
  6. Castorbean
  7. California Sycamore
  8. Mexican Sycamore
  9. Red Willow
  10. Arroyo Willow
  11. Avocado
  12. Mimosa
  13. English Oak
  14. Coast Live Oak
  15. London Plane
  16. Cottonwood
  17. Black Cottonwood
  18. White Alder
  19. Titoki
  20. Engelmann Oak
  21. Cork Oak
  22. Valley Oak
  23. Coral Tree
  24. Blue Palo Verde
  25. Palo Verde
  26. Moreton Bay Chestnut
  27. Brea
  28. Mesquite
  29. Weeping Willow
  30. Chinese Holly
  31. Camelia
  32. Acacia
  33. Japanese Wisteria
  34. Black Willow
  35. Tree of Heaven
  36. Kurrajong
  37. Black Mission fig
  38. Japanese Beech
  39. Dense Logwood
  40. Mule Fat
  41. Black Poplar
  42. Carrotwood
  43. California Buckeye
  44. Canyon Live Oak
  45. Kentia Palm
  46. King Palm
  47. Tamarix
  48. Red Flowering Gum
  49. American Sweetgum
  50. Honey Locust
  51. Brazilian Coral Tree
  52. Purple Orchid Tree
  53. Council Tree
  54. Tulip Wood
  55. Chinese Flame Tree
  56. Laurel-leaf Snailseed tree
  57. Southern Magnolia

Management and Treatment:

Keeping trees in good health is always a good defense against disease. Healthy trees are more likely to recover quickly from an attack.

Early detection of infestation and sanitary removal of the infested branches will help reduce vector populations and the spread of this pest-disease complex.

Chemical and biocontrol management strategies are currently being investigated.

APC is offering treatments as suggested from preliminary results from ongoing pesticide experiments. Treatments are available for trees with light-moderate infestation as well as prevention treatments.

It is important to note that the chance of saving a moderate to heavily infested tree is very low. 

Ensure a qualified, trained and experienced applicator is caring for your trees.

For additional information please visit the following website: