Association between Dendroctonus valens and black stain root disease on ponderosa pine in the Sierra Nevada of California

Abstract

AbstractThe host-colonization behavior of the red turpentine beetle, Dendroctonus valens LeConte (Coleoptera: Scolytidae), was investigated in stands of ponderosa pine, Pinus ponderosa P. & C. Lawson (Pinaceae), with black stain root disease in the central Sierra Nevada of California. By felling live trees, we found that trees with pitch tubes produced during the initiation of tunneling by D. valens had a significantly higher incidence of black stain root disease, caused by Leptographium wageneri var. ponderosum (Harrington et Cobb), than trees without pitch tubes. Trees with the most D. valens pitch tubes had the greatest likelihood of being diseased. Additionally, observations over a 3-year period revealed that trees with D. valens pitch tubes had a significantly higher mortality rate than trees without pitch tubes. Infection by L. wageneri was confirmed for most of the trees that died, and death typically did not occur without mass attacks by the western pine beetle, D. brevicomis LeConte, and (or) the mountain pine beetle, D. ponderosae Hopkins. Trees with the most D. valens pitch tubes had the highest mortality rate. An experiment was conducted to compare the attraction of D. valens and other insects to wounded-diseased, wounded-symptomless, and unwounded trees. More D. valens, Spondylis upiformis Mannerheim (Coleoptera: Cerambycidae), and Hylastes spp. (Coleoptera: Scolytidae) were attracted to wounded trees than to unwounded trees. Catches of these beetles on wounded-diseased trees were not significantly different from catches on wounded-symptomless trees.