INVASIVE SHOTHOLE BORER
About

Invasive shothole borer (ISHB) is a type of beetle that is smaller than a sesame seed, but can infest and harm a variety of trees. The beetle presents an ongoing management issue for urban and riparian forests in southern California. The name “shothole borer” comes from the characteristic holes left in the bark by the beetle entering or exiting a tree. 

 

As a type of ambrosia beetle, these insects carry spores of a symbiotic fungus. This fungus grows and spreads in the wood of the tree, providing the food source that the beetles depend on to grow and reproduce inside the tree. As the beetles and their symbiotic fungus colonize and grow within a tree, the fungus will block the tree’s vascular system and the transport of water and nutrients. This causes damage to the trunk and branches of the infested tree. An ISHB infested tree can decline in health, and ISHB can kill the tree if the infestation is severe enough.

Sticky Panel Trap
Sticky Panel Trap

A sticky panel trap displaying two ISHB females (circled in red), found at the Louis Rubidoux Parkland and Pecan Grove in Jurupa Valley, CA.

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Figure 1
Figure 1

ISHB female and exit hole is about the size of a medium ballpoint pen.

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Figure 2: Infested Tree
Figure 2: Infested Tree

Bole and upper branches of London Plane with ISHB injury/infestation.

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Sticky Panel Trap
Sticky Panel Trap

A sticky panel trap displaying two ISHB females (circled in red), found at the Louis Rubidoux Parkland and Pecan Grove in Jurupa Valley, CA.

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What We Do
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We've surveyed over 6000 trees in the Inland Empire so far, at 250 different locations!

Currently, the IERCD conducts the ISHB program, a multi-year collaborative program with the objective of monitoring the spread and contributing to management of ISHB within district boundaries. The area covered by this program includes San Bernardino County and Riverside County, and specifically focuses on the upper Santa Ana and Mojave River watersheds as well as urban parks. The monitoring work includes trapping and surveying work. Trapping for these insects involves deploying sticky panel traps with Quercivirol lures in strategic locations (riparian areas, green spaces), and the survey component involves  examining individual trees at various locations (parks and green spaces) for signs of ISHB infestation.

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Resources
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