Second Science Symposium
January 18 - 21, 2005
Evaluation of Fungicides for the Control of Phytophthora ramorum Infecting Rhododendron, Camellia, Viburnum and Pieris
S.A. Tjosvold and D.L. Chambers, University of California Cooperative Extension (UCCE), 1432 Freedom Blvd, Watsonville, CA 95076; and S.Koike, UCCE, 1432 Abbott St. Salinas, CA. 93901
Phytophthora ramorum has been detected infecting ornamental hosts in European nurseries and gardens beginning in1993, and detected in North American nurseries beginning in 2000. Nurseries need a comprehensive program to insure that nursery stock remain disease free. Fungicides could be part of an integrated pest management approach to meet that goal. It will be especially important to prove that fungicides are not masking symptoms and the detection of the pathogen.
This paper presents the findings of extensive fungicide
evaluations for the prevention and eradication of P. ramorum on four important
ornamental nursery hosts: Rhododendron (‘Cunningham’s
White’ and R. ‘Irish Lace’), Camellia (C.
japonica ‘Elena Nobile’), Pieris (P. japonica
‘Whitewater’), and Viburnum (V. tinus ‘Compacta’).
First, we screened prospective fungicides by evaluating the preventative
control of a wide range of commercially-available and experimental fungicides.
Second, we selected the fungicides that provided the best efficacy in
the fungicide “screen” and repeated these applications to
determine their residual action to prevent infection. With this information,
a grower can determine how frequently fungicides would need to be applied
under environmental conditions that favor disease. Efficacy was also judged
by how well the pathogen was recovered from lesions resulting from infections.
Finally, the curative potential of these fungicides were judged by the
success of recovery of the pathogen from lesions that were treated with
| Coordinated by:
USDA Forest Service Pacific Southwest Research Station
University of California Integrated Hardwood Range Management Program,
Center for Forestry, Division of Agriculture and Natural Resources, and
California Oak Mortality Task Force
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