EFFECT OF INTERACTIONS BETWEEN FUSARIUM, RHIZOCTONIA, AND PYTHIUM ON ROOT AND RHIZOME ROT OF ALSTROEMERIA

The effect of Fusarium oxysporum (F), Pythium irregulare (P), and Rhiz octonia solani (R) singly and in combination on root and stem rot of A lstroemeria cv. 'Jacqueline' showed that the average number of stems a nd stem height per plant varied with the pathogen treatment. Each path ogen alone caused significantly greater mortality than the non-inocula ted treatment. P plus R together were significantly more severe than P alone, but the combination of the three pathogens induced the greates t plant mortality. Among combinations of any two pathogens, only the m ixture of F and P caused a significantly greater plant mortality than either pathogen alone, suggesting synergism. Pathogens were readily re covered (over 93 %) from the inoculated rhizomes except in the treatme nts of F plus P, P plus R, and F plus P plus R from which 20.3, 53.3, and 15 % isolation rates of P. irregulare were obtained, respectively. Nevertheless, the pathogens were always re-isolated from the soilless mix of all treatments.