CONTROLLED ENVIRONMENT STUDIES ON THE INFECTION OF EMEX AUSTRALIS BY PHOMOPSIS-EMICIS

The effect of temperature, dew period, inoculum concentration and host maturity on the growth and development of Emex australis after inocul ation with Phomopsis emicis was studied in controlled environments. Di sease was assessed by recording changes in the length of stems, number of fully expanded leaves, dry weights, number of fruits and disease s everity index. Disease was as severe at 18 degrees C as it was at 28 d egrees C. There was a trend of increased disease with longer dew perio d. Inoculum concentrations of 1 x 10(6) and 1 x 10(7) conidia per mi r esulted in a significant net reduction in stem growth compared with lo wer concentrations. Progressively higher disease ratings occurred as t he inoculum concentration increased to 1 x 10(7) conidia per mi. There were no significant effects of inoculation with P. emicis on either s eedlings, rosettes or flowering rosettes, but 10-week-old plants were highly susceptible to infection and stem collapse. The implications of these results for the potential development of P. emicis as a mycoher bicide are discussed.