<p><strong>Background</strong>: <em>Arceuthobium vaginatum</em> subsp. <em>vaginatum</em> (BM; black mistletoe) and globosum</em> <em>grandicaule</em> (YM; yellow mistletoe), are two parasitic plant species abundant in the forests of northern central Mexico Central America, affect 43% <em>P. </em><em>hart</em>&l...

Presented here are new combinations made in advance of publication an Annotated Checklist for the Flora Nevada. New Aliciella latifolia var. imperialis, Androsace elongata acuta, Arceuthobium abietinum grandae, magnificae, mathiasenii, wiensii, Artemisia cana bolanderi, Askellia pygmaea ramosa, Boechera fernaldiana vivariensis, Calystegia sepium limnophila, Camissoniopsis pallida hallii, Cassio...

ROBERT E SCHARPF is project leader, forest disease research, with headquarters in Berkeley, Calif. He earned a bachelor's degree in forestry (1953) at the University of Missouri, and a master's degree in forestry (1957) and a doctorate in plant pathology (1963) at the University of California, Berkeley. He joined the Forest Service in 1960 and has been with the Station's staff since then. He ea...

Approximately 3.200 trees in young mixed~conifer stands were examined for pest activity and human-caused or mechanical injuries, and approximately 25 percent of these trees were randomly selected for stem analyses. The examination of trees felled for stem analyses showed that 409 (47 percent) were free of pests and 466 (53 percent) had one or more pest categories. Incense~cedar contained the fe...

1. Intraguild predation occurs when top predators feed upon both intermediate predators and herbivores. Intraguild predators may thus have little net impact on herbivore abundance. Variation among communities in the strength of trophic cascades (the indirect effects of predators on plants) may be due to differing frequencies of intraguild predation. Less is known about the influence of variatio...