The response of saprotrophic beetles to coast live oaks infected with Phytophthora ramorum

Abstract

Saprotro phic ambrosia and bark beetles (Coleoptera: Scolytidae) tunnel into the bark overlying cankers caused by Phytophthora ramorum in coast live oaks, Quercus agrifolia. These insects are characteristically reported to colonize freshly dead or moribund trees (Furniss and Carolin, 1977). However, the initial attacks by these beetles on P. ramorum-infected coast live oaks are limited to the bleeding cankers. In a disease progression study (McPherson and others, 2005), we found that beetles were present in about 50 percent of all bleeding trees in each of four years and every bleeding tree that died following beetle colonization had been attacked while the foliage was healthy. We have several lines of evidence from field studies suggesting that beetles play significant roles in sudden oak death (SOD). Beetles preferentially colonize bleeding cankers, catastrophic bole failure of bleeding trees is strongly associated with beetle tunnels, ambrosia beetles, particularly Monarthrum spp., require sound, undecayed wood, and the development of Hypoxylon thouarsianum fruiting bodies consistently follows beetle colonization.

Parent Publication

• Proceedings of the sudden oak death second science symposium: the state of our knowledge

Citation

McPherson, Brice A.; Ebilgin, Nadir; Wood, David L.; Svihra, Pavel; Storer, Andrew J.; Standiford, Richard B. 2006. The response of saprotrophic beetles to coast live oaks infected with Phytophthora ramorum. In: Frankel, Susan J.; Shea, Patrick J.; and Haverty, Michael I., tech. coords. Proceedings of the sudden oak death second science symposium: the state of our knowledge. Gen. Tech. Rep. PSW-GTR-196. Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture: 419-421