Invasive Shot Hole Borers (ISHB) (Part I)

Invasive Shot Hole Borers (ISHB) (Part I)

There are two types of Invasive Shot Hole Borers that we are concerned about in Santa Barbara County; the Polyphagous Shot Hole Borer and the Kuroshio Shot Hole Borer. The two beetles look the same, but are genetically different and can be identified using DNA analysis. Both shot hole borers are a group of ambrosia beetles that make tiny entry holes in trees.They are ambrosia beetles because they carry a symbiotic fungus with them. The fungus (Fusarium spp.) is carried along by female in special organs in her mouth parts and is used to infest the host plant.  The beetles farm the fungus and both adult beetles and larvae feed on fungus. A mated female will find a suitable host and bore into it to create galleries (a series of tunnels) to farm the fungus and lay her eggs.  These shot hole borers infest healthy trees, but the fungus causes the tree to die slowly by clogging its vascular system and preventing the movement of water and nutrients.  Once the tree can no longer sustain fungal growth, the beetles will fly to a new host.  They spend a majority of their lives within the galleries inside the tree (this makes it very difficult to control the beetles). 

The female (a) is darker and slightly larger than the male (b).