2018 ASHS Annual Conference

Pawpaw (Asimina triloba) is a tree fruit native to the Eastern United States and is grown on a small-scale commercially as a niche crop for local markets. A leaf and fruit fungal spot has been observed in pawpaw consisting of a complex of Mycocentrospora asiminae, Rhopaloconidium asiminae Ellis and Morg., and Phyllosticta asiminae Ellis and Kellerm. Symptoms include tan spots with dark brown borders on leaves, and dark brown to black superficial spots on the fruit epidermis, followed by cracking of fruit. In some pawpaw varieties, such as ‘Sunflower’ and ‘Susquehanna’, this disease can cause significant loss of yield. Sulfur is known to be the oldest of all pesticides, although sulfur based fungicides are usually applied as a preventive measure and not a cure. The objective of this study was to determine the efficacy of organic certified sulfur based fungicide for the management of leaf and fruit fungal spot in ‘Sunflower’ and ‘Susquehanna’ varieties of pawpaw. The testing of fungicide was conducted on KSU Harold R. Benson Research and Demonstration Farm in Franklin County, Kentucky. Sulfur sprays (water control, 0.05 lbs/gal and 0.1 lbs/gal) were applied after fruit set during mid-May. Disease incidence was scored in treatment and control groups of two given varieties. Quantification of disease was done by visually scoring the percentage coverage of lesions on treatment and control fruit. The selection 'Sunflower' had a significantly higher incidence of Phyllosticta lesion coverage(20.9%) compared to 'Susquahanna' (13.8%). There was also positive correlation between cracking and fungal lesion as well as fruit weight and cracking.

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