Submitted to: American Phytopathological Society
Publication Type: Abstract Only
Publication Acceptance Date: 9/4/1997
Publication Date: N/A
Technical Abstract: In the Lower Rio Grande Valley of Texas (LRGV), Didymella bryoniae (Aiersw.) Rehm commonly causes lesions in the crown and foliage of melons (Cucumis melo L.) but rarely on fruit. Benomyl drenches are routinely used for control, but in spite of applications a severe epidemic of gummy stem blight (GSB) occurred in Spring-1997 resulting in numerous corky brown lesions (1-3 mm dia) below the epidermis of cantaloupe fruit. D. bryoniae isolates (137) were obtained from infected fruit and vines at six locations in the LRGV. In vitro tests indicated that the EC50 for benomyl against mycelial growth was >5.0ug/ml for 92% of the isolates. Isolates with an EC50 of >5.0ug/ml are considered insensitive to benomyl. Most isolates insensitive to benomyl were also insensitive to thiabendazole. Azoxystrobin, myclobutanil, tebuconazole, and triflumizole at 5.0 ug/ml effectively suppressed conidial germination and mycelial growth in vitro. These fungicides also prevented development of GSB symptoms on inoculated seedlings in growth chamber studies.