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Ecology and Epidemiology

Inoculum Potential in Relation to Biological Control of Fusarium Wilt of Peas. Stephen O. Guy, Former Research Assistant, Colorado State University, Fort Collins 80523, Present address of senior author: Plant Pathology Department, University of California, Riverside 92502; Ralph Baker, Professor of Botany and Plant Pathology, Colorado State University, Fort Collins 80523. Phytopathology 67:72-78. Accepted for publication 27 May 1976. Copyright 1977 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-67-72.

Addition of chitin or cellulose to soil induced changes in symptom development of Fusarium wilt of peas. In log-log transformations of inoculum density-disease severity data, however, curves were parallel regardless of treatment indicating constant relative changes in infection rates directly correlated with inoculum density. At any given inoculum density, chitin in soil decreased disease severity slightly but significantly compared with nonamended controls. Chitin in soil, however, had no influence on survival rate (in this case, decrease in inoculum density over time) of the pathogen in comparison with nontreated soil. A cellulose amendment increased disease severity slightly in comparison with controls but this increment could be explained by the increase of inoculum density of the pathogen as a result of adding the amendment. Log-log transformations of inoculum density-disease severity curves indicated slope values not significantly different from 0.67, which conformed to those predicted for fixed inoculum and moving infection courts.

Additional keywords: Fusarium oxysporum f. sp. pisi Race 5, Pisum sativum, soil fungi.