Publication no. D-2000-1212-02R

Effect of Temperature and Water Potential on Survival and Mycelial Growth of Phaeomoniella chlamydospora and Phaeoacremonium spp. E. C. Whiting, A. Khan, and W. D. Gubler, Department of Plant Pathology, University of California, Davis 95616. Plant Dis. 85:195-201. Accepted for publication 2 November 2000. Copyright 2001 The American Phytopathological Society.

Phaeomoniella chlamydospora, a species of Phaeomoniella, and two species of Phaeoacremonium, P. inflatipes and P. aleophilum, have been associated with young grapevine decline in major production regions of California. Phaeomoniella chlamydospora has been isolated from healthy vines and inoculated but non-symptomatic vines and rooted cuttings. Effects of temperature and water potential on fungal response in culture were investigated to find effective control strategies for nurseries. Mycelial growth rates at temperatures 5 to 37ºC showed a quadratic response with optimum growth rates for Phaeomoniella chlamydospora and P. aleophilum at 25ºC and at 30ºC for P. inflatipes. Response to water potential varied by isolates within a species, but isolates of Phaeomoniella chlamydospora were not sensitive to decreasing water potential. A conidial suspension and plugs of agar with mycelia were placed in glass vials and incubated in hot water for 15 to 120 min. Conidia were sensitive to hot-water treatment after 15 and 30 min. Nevertheless, mycelia of P. inflatipes from agar plugs grew on potato dextrose agar at 22ºC after 120 min incubation at 51ºC. Because the fungi were not killed by incubation in glass vials at 51ºC, methods other than hot-water treatment may be more effective in eliminating Phaeomoniella chlamydospora and Phaeoacremonium spp. from dormant vine cuttings. Additional keywords: Vitis vinifera.