METALAXYL SENSITIVITY AND AGGRESSIVENESS OF

Abstract

Leaf blight caused by Phytophthora colocasiae is the most devastating disease of taro (Colocasia esculenta). P. colocasiae isolates belonging to four morphogroups were assessed for their aggressiveness and reaction to the metalaxyl fungicide Ridomil Gold 60WP. Based on sporangia morphology and partial β tubulin sequence homology all fungal isolates associated with and recovered from infected leaves were identified as P. colocasiae. Significant differences (P< 0.05) were observed among the isolates based on the various parameters (incubation period, lesion size and sporangia produced) taken into consideration. Similarly, the various isolates reacted differently to the test fungicide. Eleven of the isolates were considered to be moderately resistant, whilst 69 (86.2%) were found to be susceptible to the fungicide. None of the tested isolates was metalaxyl-resistant. Results of the study showed differences in the organism causing taro leaf blight disease in Ghana based on their aggressiveness potentials as measured by the epidemiological components. Also the lack of an identified resistant isolate shows the potential of employing metalaxyl based fungicide in managing taro leaf blight caused by P. colocasiae.