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...

A broader, more comprehensive concept of forest pest management is needed to make it a really integral part of forest resource management. A generalized model structure of a forest pest management system is presented, and the major components are discussed briefly. Predictive models are the primary mechanism of information flow to decision and action in the system. General considerations affect...

Plants are in constant communication with a multitude of diverse organisms. Some symbioses, such as the association of nitrogen-fixing bacteria and mycorrhizal fungi with plant roots, are beneficial to the plant. Others, such as the interaction of plants with viral, microbial, fungal, and nematode pathogens, are harmful. Most plant-organism interactions go unnoticed simply because they are unde...