Efficacy of Fungicides for Control of Rosette and Post-harvest Fruit Diseases of Blackberries

Authors: Smith, Barbara; Miller Butler, Melinda

Submitted to: International Journal of Fruit Science
Publication Type: Abstract Only
Publication Acceptance Date: 4/15/2015
Publication Date: 6/15/2015
Citation: 2015 Smith, B.J., Miller Butler, M.A. 2015. Efficacy of Fungicides for Control of Rosette and Post-harvest Fruit Diseases of Blackberries. Eleventh International Rubus Ribes Symposium Program. p. 28.

Interpretive Summary:

Technical Abstract: Rosette disease (caused by the fungus Cercosporella rubi) is often severe on erect blackberries grown in the southeastern U.S. and, if not controlled, may limit fruit production. A series of trials were conducted in south Mississippi to determine fungicide efficacy and optimum timing of applications. In each trial 8 to 10 fungicides were applied to rosette-susceptible, erect, thorny blackberry cultivars from early leaf emergence through harvest. Rosette severity was rated the following spring when rosettes were easily visible. Fruit were harvested from each plot and assessed within 5 days for post-harvest disease symptoms and fruit quality. Among fungicides tested, azoxystrobin (Abound), cyprodinil + fludioxonil (Switch), and pyraclostrobin + boscalid (Pristine) were the most effective for rosette and post-harvest disease control. The results of these and earlier trials demonstrated that fungicides are most effective for rosette control when applications began prior to bloom and continue until the fungus has ceased to sporulate about a month after harvest. Fungicides effective against rosette also reduced the severity of post-harvest fruit diseases and common foliar diseases such as Septoria Leaf Spot and Leaf and Cane Rust.