Apples are the most commonly grown fruit in Kentucky.  Approximately 672 orchards produce between 450,000 and 750,000 bushels of apples per year, a value of $24.4 to $40.6 million.  Most orchards in Kentucky have an agritourism focus and consist of mixed fruit plantings or specialty produce.  Apple, blueberry, grape, peach, and strawberry are all susceptible to anthracnose diseases caused by the same family of fungi.  Bitter rot of apple is the most significant of these diseases with an average yield loss of 30% (range 10% to 90%).  Anthracnose fruit rots of other fruits are less severe and only cause significant losses during periods of excess rain.

This study of bitter rot on apple led to the phylogenetic and morphological identification of six species of Colletotrichum that can infect or cross infect apple, blueberry, and strawberry.  New information indicated that management of anthracnose diseases on blueberry (ripe rot) and strawberry (anthracnose), neither of which cause significant disease loss, may be necessary to prevent spread to nearby apples. Interruption of the cross-infection cycle is an important step in mitigating disease losses in apple.

Understanding the fungi that cause bitter rot on apple and anthracnose on other fruits required large numbers of samples, multiple years of study, and a multifaceted research approach.   This project was possible through a partnership between Extension and research faculty in the Department of Plant Pathology.  Expertise of collaborators came together between 2012 and 2020 to study anthracnose diseases across Kentucky.  By the end of the study, the team developed grower trainings, fact sheets, and new management recommendations that are helping growers better understand spread and infection within their orchards.  Also resulting were peer reviewed research publications that are vital to pathologists in all apple growing regions of the world, two graduate student degrees, and several undergraduate research internships and educational opportunities.  This project will continue to expand to provide support for growers, as well as student research opportunities.