|Miller Butler, Melinda
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/14/2016
Publication Date: 4/4/2016
Citation: Smith, B.J. and Miller-Butler, M.A. 2016. Effect of nitrogen fertilization and fungicides on Botryosphaeria stem blight lesion development on detached stems. Abstract Book XI International Vaccinium Symposium, University of Florida Gainesville, FL. Page 179
Technical Abstract: Botryosphaeria stem blight is a destructive disease of blueberries. Field observations indicate stem blight is more severe on vigorous plants than on slower growing plants. Two studies compared the effect of two types of fertilizers applied at four rates and nine fungicides on lesion development following inoculation of detached stems from two-year old potted plants of the rabbiteye cultivar, Tifblue. Partially-hardened stems were wounded, inoculated with Botryosphaeriaceae isolates, and incubated for 10 to 21 days in a growth chamber. Plants in the fertilizer study were inoculated with a virulent isolate of Botryosphaeria dothidea and those in the fungicide study were inoculated with the same isolate plus three other Botryosphaeriaceae isolates. Results of the fertilizer study showed no differences in lesion length 10 days after inoculation on stems from plants receiving 1, 2, 4, and 8 times the recommended levels of liquid or slow release fertilizers. Lesions were longer on stems from plants receiving these fertilizer treatments compared to those from plants that were not fertilized. In the fungicide study, plants were sprayed with nine fungicides or with water. Stems were wounded either immediately before or 24 hr after fungicide application, collected 24 hr after fungicide application, and inoculated within 6 hours. Twenty-one days after inoculation among stems wounded before fungicide application, those treated with pyraclostrobin, fosetyl aluminium, or pyraclostrobin + boscalid had the shortest lesions; among those wounded after fungicide application, there were no differences in lesion length between the untreated control and any fungicide treatment. Two B. dothidea and two Neofusicoccum sp. isolates were grown for 4 days on agar amended with the same nine fungicides at a range of concentrations. Growth of each isolate was significantly reduced on agar amended with azoxystrobin, pyraclostrobin, tebuconazole, propiconazole, pyraclostrobin + boscalid or cyprodinil + fludioxonil at concentrations above 0.1 mg/L. Keywords:Vaccinium virgatum, Vaccinium ashei, Botryosphaeria dothidea, Neofusicoccum sp.