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Poster: Biology & Disease Mgmt: Cultural Control


Evaluating biodegradation treatments for the reduction of inoculum and incidence of citrus black spot Phyllosticta citricarpa in Florida citrus groves
K. RODRIGUES (1), T. Hobbs (1), M. Dewdney (1) (1) CREC, University of Florida, U.S.A.

The fungal disease citrus black spot (CBS) has become an increasing problem in Florida citrus groves. We conducted a 3-year study to evaluate the effect of 5% urea (9.4 kg/190 l water/0.4 ha), Soil-Set (142 ml/190 l water/0.4 ha), and a water control on the level of the P. citricarpa or the morphologically similar citrus endophyte P. capitalensis in the leaf litter and subsequent CBS incidence on fruit in a Valencia grove in Immokalee, FL. The experiment was a randomized complete block design with three rows per treatment (trt) and four blocks. Leaf litter samples were collected from arbitrarily selected trees at time of treatment and then three times biweekly post-treatment application. For every collection, 100 leaves/trt/block were inspected for fungal sporocarp presence and each fungus was quantified via qPCR. The disease incidence on fruit was collected for 50 fruit/tree on 125 trees/trt/block. Fungal DNA levels were analyzed with a 3-way ANOVA and fruit disease incidence by contingency table analysis and chi-square tests. Leaf litter DNA had a significant interaction (P < 0.0001) between block x trt x collection date. For the incidence of disease on fruit, significant treatment effects were seen in 2015 (P = 0.002) and 2016 (P < 0.0001) with Soil-Set reducing disease incidence by 29.6% and 26.5%, respectively but not with urea. Soil-Set may enhance the efficacy of fungicide applications for the management of CBS.