2019 ASHS Annual Conference

Pawpaw is the largest tree fruit native to the eastern United States demonstrating potential as a fruit crop with commercial value. Leaf and fruit fungal spot a disease consisting of a complex of Mycocentrospora asiminae, Rhopaloconidium asiminae Ellis and Morgan, and Phyllosticta asiminae Ellis and Kellerm has been observed in pawpaw. Major symptoms include circular to angular or irregular, small to large tan spots with dark brown borders on leaves and dark brown to black spots on the fruit epidermis. Cracking of fruit is observed in severe cases. A positive correlation between fruit cracking and Phyllosticta coverage on the epidermis was found in previous research at Frankfort, KY. Sulfur and copper are essential nutrients for plants and are used to control many fungal diseases in plants. The objective of this study was to determine the efficacy of sulfur-and copper-based fungicides for the management of leaf and fruit fungal spot in ‘Sunflower’ and ‘Susquehanna’ cultivars of pawpaw. The experiment was conducted at the Kentucky State University (KSU) Harold R. Benson Research and Demonstration Farm in Frankfort, Kentucky in 2018. Fruit clusters were treated with two levels of each fungicide (sulfur at 25 or 50 ml/800 ml water or Copper at 3.12 or 12.5 ml/800 ml of water); water applied as a control. Insecticidal soap was used as an adjuvant in all treatments, including control, at 155 μl per 800 ml of water. Treatments were applied at 7- to 14- day intervals from 14^th June 2018 to 23^rd August, 2018. Quantification of disease on fruit was done by visually scoring the percentage of the fruit surface covered by lesions. Disease symptoms on leaves were quantified using Image-pro version 6.3 software. Data from untreated fruit clusters and leaves from the same tree were taken as an alternative control. The data were analyzed for analysis of variance and mean treatment differences using CoStat statistical software. In fruit, the high concentration sulfur and control had the least amount of disease coverage in comparison to other treatments and alternative control; alternative control had a significantly higher amount of disease coverage in comparison to other treatments. In leaves, all four treatments had significantly less disease coverage compared to control and alternative control. Single year data is not enough to draw a fixed conclusion about the effectiveness about these fungicides as results on fruit and leaves differed in this study; therefore this study should be replicated.