INSECT INFESTATIONS AND INCIDENCE OF WESTERN GALL RUST AMONG PONDEROSA PINE SOURCES GROWN IN THE CENTRAL GREAT-PLAINS

Six seed sources in two 22-yr-old ponderosa pine, Pinus ponderosa vari ety scopulorum Engelmann, provenance plantings in Hastings, NE, and Al liance, NE, were evaluated for abundance of Rhyactonia bushnelli, Reti nia metallica, Dioryctria spp., and Peridermium harknessii. The 6 sour ces 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 plant ings, R. bushnelli abundance was lower on the 3 taller sources (720, 7 21, 757) than on the 3 shorter sources (764, 833, 835) similar to what was observed previously. The abundance of current and old R. metallic a was low in bod plantings and did not vary with source. At the Allian ce planting, taller sources had more total Dioryctria spp. than shorte r sources. P. harknessii galls were present on every sampled tree in t he Hastings planting and occurred only on a few trees sampled at Allia nce, but no source differences were detected. Abundance of R. bushnell i was positively correlated with previous-year R. metallica at Allianc e and current-year R metallica at Alliance and negatively correlated w ith II harknessii abundance at Hastings. Interactions among environmen tal, host, and insect factors probably account for these correlations.