Thursday, May 8, 2014

Polyphagous shot-hole borer beetle

A new beetle/fungal complex was recently detected on avocado and other host plants in Los Angeles, Orange,  San Bernardino, and San Diego Counties.  Photo shows symptoms to look for on the trees. Contact Steven Smith Landscape, Inc. for a consultation.

"The two fungal species are  Fusarium euwallaceae and Graphium sp., which form a symbiotic relationship with a recently discovered beetle that is commonly known as the polyphagous shot hole borer (PSHB, Euwallacea sp.) (Fig. A). Together, they cause the disease Fusarium dieback (FD). When the beetle burrows into the tree, it inoculates the host plant with the fungus (Fig. D), which is carried in its mouthparts in a structure called mycangia. The fungus attacks the vascular tissue of the tree, blocking the transport of water and nutrients from the roots to the rest of the tree, and eventually causing branch dieback. The beetle larvae live in galleries within the tree and feed on the fungus.  FD has been observed on more than 110 different plant species in California, including many species common in urban landscapes and on such agriculturally important species as avocado, olive and persimmon." From Akif Eskalen PhD, UC Riverside