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Title: Management of gummy stem blight of cantaloupe in south Texas

Author
item MILLER, MARVIN - TEXAS A&M, WESLACO, TX
item SALDANA, RICARRDO - TEXAS A&M, WESLACO, TX
item Bruton, Benny

Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 3/30/2006
Publication Date: 6/1/2006
Citation: Miller, M.E., Saldana, R.R., Bruton, B.D. 2006. Management of gummy stem blight of cantaloupe in south Texas [abstract]. Phytopathology. 96(6):S79.

Interpretive Summary:

Technical Abstract: In the Lower Rio Grande Valley of Texas (LRGV), Didymella bryoniae (Auersw.) Rehm commonly causes lesions in the crown and foliage of cantaloupe (Cucumis melo L.) but only occasionally on fruit. In Spring-1997, a severe gummy stem blight (GSB) epidemic occurred resulting in numerous corky-brown lesions (1-3) mm dia) below the epidermis of cantaloupe fruit. D. bryoniae isolates (137) were tested for sensitivity to the commonly used fungicide, benomyl, and In vitro tests indicated that the EC50 for benomyl against mycelial growth was >5.0ug/ml for 92% of the isolates, indicating insensitivity to benomyl. Azoxystrobin, a strobilurin-based fungicide, was registered for GSB control in 1998 and was highly effective. In 2003, 28 cantaloupe stem isolates of D. bryoniae were obtained from six locations in the LRGV and 25 of the isolates were insensitive to azoxystrobin. Since the D. bryoniae population has become highly resistant to two fungicide groups in less than ten years, different fungicide groups were evaluated for their potential use in a GSB management program. Boscalid + pyraclostrobin, cyprodinil, chlorothalonil + azoxystrobin, cyhprodinil + fludioxonil, boscalid, azoxystrobin, and pyroclostrobin effectively controlled stem and fruit lesions caused by D. bryoniae when alternated with chlorothalonil.