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Poster: Biology & Disease Mgmt: Chemical Control


Fungicides for management of Sclerotium rolfsii and enhanced overwintering survival of stevia
A. KOEHLER (1), H. Shew (1) (1) NCSU, U.S.A.

Stevia (Stevia rebaudiana) is an herbaceous perennial under evaluation as a new crop in NC. Stem rot caused by Sclerotium rolfsii results in wilting, rapidly followed by root and stem necrosis. Currently there are no fungicides labeled for use on stevia, which will limit expansion of commercial production. Initial fungicide efficacy trials were established in July 2014 in naturally infested soil in Kinston, NC. Treatments included azoxystrobin, flutolanil, and tebuconazole applied at 3 timings. This trial was repeated in May and July of 2015 in adjacent field space. Stand counts were taken to determine disease incidence and overwintering survival of stevia crowns. All fungicides reduced incidence of stem rot compared to the control. In 2015, azoxystrobin was correlated with enhanced overwintering survival (mean survival rate, 66%) compared to other fungicide treatments (19%) and the untreated control (16%). In 2015, a second field site was established in Rocky Mount, NC to evaluate the effect of late season applications of azoxystrobin and pyraclostrobin. Both fungicides resulted in higher root weights and greater new shoot production compared to the control in spring 2016. Final stand counts of all treatments will be taken in spring 2016 to establish overwintering survival rates. Successful overwintering of stevia crowns directly impacts the profitability of second and third year harvests and the likelihood of long term establishment of stevia in NC.