Effect of temperature and water potential on survival and mycelial growth of Phaeomoniella chlamydospora and Phaeoacremonium spp.

Phaeomoniella chlamydospora, a species of Phaeomoniella, and two species of Phaeoacremonium, P. inflatipes and P, aleophilum, have been associated wit h young grapevine decline in major production regions of California. Phaeom oniella chlamydospora has been isolated from healthy vines and inoculated b ut non-symptomatic vines and rooted cuttings. Effects of temperature and wa ter potential on fungal response in culture were investigated to find effec tive control strategies for nurseries. Mycelial growth rates at temperature s 5 to 37 degreesC showed a quadratic response with optimum growth rates fo r Phaeomoniella chlamydospora and P. aleophilum at 25 degreesC and at 30 de greesC for P. inflatipes. Response to water potential varied by isolates wi thin a species, but isolates of Phaeomoniella chlamydospora were not sensit ive 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 t o 120 min. Conidia were sensitive to hot-water treatment after 15 and 30 mi n. Nevertheless, mycelia of P. inflatipes from agar plugs grew on potato de xtrose agar at 22 degreesC after 120 min incubation at 51 degreesC. Because the fungi were not killed by incubation in glass vials at 51 degreesC, met hods other than hot-water treatment may be more effective in eliminating Ph aeomoniella chlamydospora and Phaeoacremonium spp, from dormant vine cuttin gs.