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African Crop Science Journal
African Crop Science Society
ISSN: 1021-9730
EISSN: 2072-6589
Vol. 3, No. 4, 1995, pp. 519-523
Bioline Code: cs95071
Full paper language: English
Document type: Research Article
Document available free of charge

African Crop Science Journal, Vol. 3, No. 4, 1995, pp. 519-523

 en Leafspot of Taro ( Colocasia esculenta check for this species in other resources (L.) Schott) in Ghana and Suppression of Symptom Development with Thiophanate Methyl
Awuah, R.T.

Abstract

A foliar disease of taro ( Colocasia esculenta check for this species in other resources (L.) Schott) in Ghana, which manifests as diffuse, circular to irregular spots, mostly on older leaves ultimately resulting in leaf blight, was found to be caused by Cladosporium colocasiae check for this species in other resources (Saw.). Isolates of C. colocasiae used in pathogenicity tests were virulent on taro but generally non-pathogenic to cocoyam ( Xanthosoma sagittifolium check for this species in other resources (L.) Schott). A study of disease progress on individual leaves of upland taro indicated that spots appear on newly unfurled leaves after 12 days and the leaf blight stage occurs 24 days later. Of sixty-four taro plantings surveyed in nineteen towns and villages, forty-six (71.9%) were growing in swamps, twelve (18.8%) under semi-upland conditions and six (9.3%) under strictly upland conditions. The disease was observed in fifty-eight (90.6%) of the plantings. It was either absent or unimportant on swamp-grown taro, moderate on semi-upland taro and most severe on the upland crop. In an upland field trial, each of the six different application rates and spray schedules tested with Topsin M (thiophanate methyl 70 WP), significantly reduced disease progress. Thus, leaf spotting disease could be effectively managed with the fungicide in the upland/semi-upland regions of Ghana.

Keywords
Cladosporium colocasiae, disease progress curve, pathogenicity, Topsin M

 
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