UC Nursery and Floriculture Alliance
University of California
UC Nursery and Floriculture Alliance

Spring 2011

Campus News compiled by Deborah Mathews


Dr. Michael Parrella, professor and chair of the Department of Entomology at UC Davis, was inducted into the California Floriculture Hall of Fame during a ceremony at the Society of American Florist’s 27th Annual Pest and Production Conference in San Diego on February 25, 2011. The award was sponsored by the Kee Kitayama Research Foundation and is given to individuals who have made significant contributions to the floriculture industry during their careers.  Dr. Parrella’s research focuses on Integrated Pest Management (IPM) strategies with an emphasis on biological control of insects on ornamental crops.

Two other UC Davis researchers who made significant contributions to the California floriculture industry recently retired. Dr. Michael Reid spent 32 years as an environmental horticulture professor and specialist, as well as associate dean for Cooperative Extension in the College of Agriculture and Environmental Sciences. He received numerous industry awards, such as induction into the California Floriculture Hall of Fame, in recognition for his work on the post harvest biology and handling of cut flowers and ornamental potted plants. Jim Thompson, Cooperative Extension specialist at UC Davis in the Department of Biological and Agricultural Engineering, retired after 35 years of service.  Thompson’s research also focused on postharvest technologies and was instrumental in introducing forced-air cooling for cut flower processing and preservation to the ornamental industry.


Dr. Deborah Mathews, UC Cooperative specialist in the Department of Plant Pathology and Microbiology, will be a presenter at the 2011 Ohio State Florist Association (OFA) Plug & Cutting Conference held on September 12-14, at the Doubletree Hotel in San Jose, California.  Mathews will be discussing virus detection and management. Other sessions at the conference will include topics such as plug and cutting principals, production inputs and pest and disease management; some sessions will be available in Spanish. For more information or to register, go to http://www.ofa.org/.

Research Update compiled by Deborah Mathews

Rose Replant Problem Apparently of Biological Nature

by F. Da Silva Rocha, M. Mundo-Ocampo, J.F. Karlik, U.K. Schuch, J.A. Smith Becker and J.O. Becker.

Victoria Avenue is an attractive botanical 4-mile long parkway in Riverside. The roadway, created in 1892, is planted along each edge of the median with rose bushes (Rosa sp. ‘Ragged Robin’). Difficulties in replanting own-rooted roses led us to focus on potential soil-borne causes for the problems. Soil samples from the root zone of hundreds of rose bushes were pooled and extracted for enumeration of plant parasitic nematodes. Although lesion (Pratylenchus vulnus), root-knot (Meloidogyne hapla) and dagger nematodes (Xiphinema sp.) were present in nearly all samples, none of the nematode species occurred at population densities likely to cause replant problems.

In two lath house trials, rose plant growth was assessed in response to various soil treatments. The Victoria Avenue replant soil was either fumigated with methyl iodide or incubated in a water bath at temperatures of 104, 122, 140 or 158?F for 30 minutes. A non-treated sample served as a control. In a second trial, replant soil was diluted with the same but fumigated soil at increasing ratios. Two-year-old bare-root roses ‘Space Odyssey’ on rootstock ‘Dr. Huey’ (Weeks Roses, Upland, CA), were planted into 2-liter plastic pots. Both trials were conducted as a randomized complete block with 8 replications at ambient light and temperature. All pots received label rate slow-release fertilizer and were watered as needed. After 8 weeks, the number of new shoots, their average length and the number of flowers per plant were recorded. Plant weight and population density of plant parasitic nematodes were determined after 10 weeks.

In the first trial, dry weight of foliage increased linearly with increasing temperatures of the preplant soil treatment. A few lesion nematodes were found only in the non-treated control and in the 104?F treatment. Compared to the non-treated control, soil fumigation increased the average length of new shoots and the number of flowers by 56% and 48%, respectively. New root growth increased by 42%, and the foliage dry weight more than doubled. In the soil dilution trial, blooming increased from 6.7 flowers in the non-treated control to 17 per plant in the methyl iodide-treated soil. Roses grown in a mix of 10% replant soil with 90% fumigated soil showed similar growth suppression as in the non-treated control soil. The transfer of replant problem with only 10% of the original Victoria Avenue soil and its elimination by soil fumigation or pasteurization strongly suggests one or more biological factors are responsible for the replant problem.

F. Da Silva Rocha is Postdoctoral Researcher, M. Mundo-Ocampo is Staff Research Associate, J.A. Smith Becker is Assistant Specialist and J.O. Becker is Cooperative Extension Specialist and Nematologist, Department of Nematology, UC Riverside; J.F. Karlik is Farm Advisor, UC Cooperative Extension Kern County; and U.K. Schuch is Extension Specialist Environmental Horticulture and Professor, Department of Plant Sciences, University of Arizona.

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