Importance of oak ambrosia beetles in predisposing coast live oak trees to wood decay

Abstract

Attacks by the oak ambrosia beetle (Monothrum scutellare) accelerated and increased the amount of wood decay in stems of downed coast live oak (Quercus agrifolia) trees. When permethrin insecticide was sprayed on oak bark surface, the ambrosia beetles produced only one-fourth as many galleries in the sapwood as compared to sapwood beneath the unsprayed bark surface. Although decay fungi initiated infection in oak in the absence of beetles, the amount of wood decay was much greater in trees with beetle activity. The ambrosia beetles deeply penetrated the sapwood and constructed extensive galleries that hastened wood decay by decay pathogens. The insecticide inhibited beetle attack and formation of egg galleries and greatly decreased the amount of wood decay. © 2004 International Society of Arboriculture.