Partial life tables from three generations of Enaphalodes rufulus (Coleoptera: Cerambycidae).

ABSTRACT

We used life table analyses to investigate age specific mortality and to better understand the population dynamics of the red oak borer, Enaphalodes rufulus (Haldeman) (Coleoptera Cerambycidae). We continually sampled populations within 177 trees at primarily two sites in the Ozark National Forest in Arkansas throughout three (2-yr) generations. The first cohort (adults emerged in 2003) was sampled during a severe population outbreak, whereas the second and third (2005 and 2007) were sampled during the population crash that followed. Generation mortality was 94% in 2003 and 99% in both 2005 and 2007. Estimates of apparent mortality indicated that the E. rufulus population crash likely occurred during or before the first overwintering period (2003-2004) of the generation that emerged as adults in 2005. We found limited evidence for density dependent mortality, which suggest that intraspecific competition after the first active feeding period was apparently not an important mortality factor during E. rufulus development. Life tables revealed that E. rufulus larvae generally experienced the greatest apparent mortality during the second summer of active feeding (80-94%) when larvae were feeding in, and moving between phloem and sapwood. The least apparent mortality was incurred during the following spring and early summer (26-67%) when late stage larvae and pupae were deepest and most protected within sapwood or heartwood tunnels. We found very little evidence for mortality from associated species. Scarring of vascular tissue in response to E. rufulus feeding occurred during early life stages and may be an important tree resistance mechanism and E. rufulus mortality factor.