Historical dynamics of a native cerambycid, Enaphalodes rufulus, in relation to climate in the Ozark and Ouachita Mountains of Arkansas

Abstract

1. Tree-ring techniques were used to date larval gallery scars of a native wood borer, Enaphalodes rufulus (Haldeman), in host Quercus rubra L. from eight sites within the Ozark and Ouachita National Forests of Arkansas. 2. Borer densities were quantified throughout the past century as indicated by scars within host tree boles and per capita rate of increase was calculated from one generation to the next. Both of these variables were extrapolated to the regional level. 3. Scar data from 78 Q. rubra revealed that at the regional level borer population growth increased from 1976 to 2000, or 11 generations prior to a recent outbreak. Duration and intensity of eruptive behaviour were variable geographically. 4. Sites with higher outbreak densities also sustained incipient (i.e. growing) populations for a longer time period than sites with lower outbreak densities, which indicates that a greater potential for exponential increase existed at these sites because more borers were present when conditions became favourable for an outbreak. 5. An index of summer soil moisture availability explained almost half of the variation in E. rufulus population growth, which suggests that drought may have been an important causal factor in the recent outbreak.