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Optimization of fungicides for disease management and enhanced overwintering of stevia
Alyssa Koehler: North Carolina State University
<div>There are many challenges facing the establishment of stevia (<i>Stevia rebaudiana) </i>as a perennial crop in the US. Southern blight (caused by <i>Sclerotium rolfsii)</i> and Septoria leaf spot (caused by <i>Septoria sp.</i>) are the most economically important diseases in the southeast. Fungicide efficacy trials for management of these diseases were conducted between 2014 and 2017 and multiple products for management of <i>S. rolfsii </i>and <i>Septoria</i> were identified<i>.</i> Crowns from fungicide trials in 2014 were left in the field to overwinter and stand counts were taken in spring 2015 to determine percent emergence compared to final stand counts in fall 2014. Treatments that received one or more applications of the QoI (strobilurin) fungicide azoxystrobin had enhanced overwintering survival (mean survival rate, 78%) compared to other fungicides (38%), and the non-treated control (38%). In spring 2016, plots receiving QoI treatments in 2015 had higher overwintering emergence compared to controls at two locations. Roots and crowns were destructively sampled in spring 2016 and QoI treated plants had higher mean weights (62g) compared to non-treated controls (31g). Trials planted in 2016 were destructively sampled monthly for 12 months to record root weights and document fungi associated with roots throughout the growing season and overwintering. This study may open a new avenue of investigation into the role of fungicides and the root phytobiome in the vigor and survival of perennial plants.</div>

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