PREDISPOSITION OF MELALEUCA (MELALEUCA-QUINQUENERVIA) TO INVASION BY THE POTENTIAL BIOLOGICAL-CONTROL AGENT BOTRYOSPHAERIA-RIBIS

Enhancement of the canker causing ability of Botryosphaeria ribis on m elaleuca was studied with respect to stress from simulated drought, lo w temperature, and defoliation treatments. Low xylem water potential w as related to increased level of canker development and subsequent tre e mortality, Canker development was enhanced by low temperature treatm ents with alternating exposure to 6 C for 3 d followed by 4 d at 30 (/-5) C for 8 wk, Partial defoliation did not affect canker development but complete defoliation of B. ribis-inoculated ramets resulted in tr ee mortality within 4 wk. Callusing of melaleuca wounds was either red uced or prevented in stressed trees. These observations suggest that s tress induced on the tree enhances the tree-killing efficacy of this f ungus.