APS Abstracts of Presentations

Protection of grapevine pruning wounds against esca and young esca pathogens
A. ESKALEN (2), S. Rooney-Latham (1), W. Gubler (2)
(1) Califonia Department of Food and Agriculture, Sacramento, CA 95863; (2) Department of Plant Pathology, University of Califonia, Davis, CA 95616
Phytopathology 97:S33

Pruning wounds of grapevines were shown to be susceptible to infection of Togninina spp. and Phaeomoniella chlamydopsora. Conidia of P. chlamydospora and ascospores of T. minima are released during winter and spring rainfall. Field trials were conducted to examine the ability of these fungi to infect grapevine pruning wounds and examine potential fungicides for disease control. Five fungicides were tested in two locations in California. Dormant grapevines of cvs. Zinfandel and Chardonnay were pruned to 2-bud spurs in December 2004 and 2005 and treated with fungicides. One day after applying fungicides, spore suspensions (10(^6) spores/ml) of T. minima and P. chlamydospora were used to inoculate grapevines. Non-inoculated grapevines were used to determine the amount of natural infection in each field and spore suspensions were also applied to non-treated pruning wounds. Spurs were collected in late fall, sterilized vascular tissue was cultured onto potato dextrose agar (PDA) amended with tetracycline (0.1%). High infection rates were obtained from spurs inoculated with P. chlamydospora (79%) and T. minima (46%). Topsin M, Biopaste (5% Boron), Garrison and Cabrio were the best wound protectants for T. minima and P. chlamydospora in both years. These fungicides gave control of T. minima at 96%, 92%, 46%, and 65% respectively, and control of P. chlamydospora was 91%, 91%, 59%, and 85%, respectively. Treatment of pruning grapevine pruning wounds with fungicides provided economic control of esca and young esca.

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