Insect infestations and incidence of western gall rust among ponderosa pine sources grown in the central Great Plains.
Dix M.E. | Harrell M. | Klopfenstein N.B. | Barkhouse K. | King R. | Lawson R.
Six seed sources in two 22-yr-old ponderosa pine, Pinus ponderosa variety scopulorum Engelmann, provenance plantings in Hastings, NE, and Alliance, NE, were evaluated for abundance of Rhyacionia bushnelli, Retinia metallica, Dioryotria spp., and Peridermium harknessii. The 6 sources were selected for this study based on superior growth and previous susceptibility or nonsusceptibility to the aforementioned insects and pathogen. Infestation levels per tree and per branch, and proportion of infested tips were used to evaluate the influence of source on pest abundance. Abundance of the pests varied with planting. In both plantings, R. bushnelli abundance was lower on the 3 taller sources (720, 721, 757) than on the 3 shorter sources (764, 833, 835) similar to what was observed previously. The abundance of current and old R. metallica was low in both plantings and did not vary with source. At the Alliance planting, taller sources had more total Dioryctria spp. than shorter sources. P. harknessii galls were present on every sampled tree in the Hastings planting and occurred only on a few trees sampled at Alliance, but no source differences were detected. Abundance of R. bushnelli was positively correlated with previous-year R. metallica at Alliance and current-year R. metallica at Alliance and negatively correlated with P. harknessii abundance at Hastings. Interactions among environmental, host, and insect factors probably account for these correlations.
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