VIEW ARTICLE

Ecology and Epidemiology

Influence of Nutrition, Temperature, Moisture, and Gas Composition on Parasitism of Rhizopus oryzae by Syncephalis californica. W. E. Hunter, Department of Plant Pathology, University of California, Davis, CA 95616, Present address: Diamond Shamrock Chemical Co., 5639 Camellia Ave., Sacramento, CA 95819; J. M. Duniway(2), and E. E. Butler(3). (2)(3)Department of Plant Pathology, University of California, Davis, CA 95616. Phytopathology 67:664-669. Accepted for publication 13 December 1976. Copyright © 1977 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-67-664.

The influence of environment on parasitism of Rhizopus oryzae by Syncephalis californica was studied in vitro and in nonsterilized field soil. Syncephalis californica frequently was observed parasitizing R. oryzae in nature on decaying apricot fruit on soil in an orchard at Winters, California. Host and parasite populations in soil were measured at depths of 3 and 20 cm in the orchard from May through November 1973; propagules per gram of dry soil ranged from 23 to 1,847 for Rhizopus spp. and from 40 to 233 for S. californica. There were no consistent relationships between the populations of the hosts and parasite in the field. Parasitism occurred in vitro at temperatures of 15-36 C, at pH values of 4.0-7.5, and at four different carbon:nitrogen ratios. Parasitism was observed in vitro and in nonsterilized orchard soil at oxygen concentrations of 1-21% and at carbon dioxide concentrations of 0.03-5%. Soil moisture levels between saturation and field capacity, but not including saturation, were suitable for parasitism. Infection by S. californica suppressed sporulation of R. oryzae under most conditions that were suitable for growth of the host. The results indicate that S. californica is an aggressive mycoparasite capable of attacking R. oryzae under a wide set of soil environments.