Date of Award


Document Type


Degree Name

Master of Science (MS)


Plant and Environmental Science

Committee Member

Matthew A Cutulle

Committee Member

Lambert McCarty

Committee Member

Jeffrey Adelberg

Committee Member

Phillip Wadl


Sweetpotato [Ipomoea batatas L. (Lam)] growers need new technologies to manage weeds as current strategies rely on combinations of pre-emergent (PRE) or cultivation, which do not provide season long weed control. A label expansion of postemergence (POST) herbicides would be extremely beneficial to farmers and could improve weed management in sweetpotato.

Three studies were conducted at the Clemson University Coastal Research and Education Center from January 2019 to November 2020 to investigate the ability of plant hormones and ascorbic acid (AsA) to improve sweetpotato tolerance to applications of POST herbicides. An in vitro study tested bentazon injury on three different sweetpotato cultivars in an in vitro environment. The most tolerant cultivar was used in an additional experiment, where exogenous melatonin was added into the media to evaluate its ability to reduce herbicide damage. A dose-response study of two sweetpotato cultivars to increasing rates of bentazon and mesotrione was conducted. Additionally, the ability of plant hormones and AsA to reduce herbicide injury when added to the tank-mix with those two herbicides was investigated. Furthermore, the interaction between POST herbicides and additional compounds to control troublesome weeds commonly found in sweetpotato production was evaluated. A field trial study was conducted in two locations in the state of South Carolina to investigate bentazon injury, yellow nutsedge (Cyperus esculentus L.) control, and final yield, with or without the addition of plant hormones.

The first study identified the sweetpotato cultivar ‘Beauregard’ as having greater tolerance to bentazon applications when compared to the other cultivars. Additionally, melatonin reduced plant injury caused by bentazon. Specifically, melatonin incorporated at 0.1 and 1mM resulted in 32% less injury than bentazon alone and 50% more plant mass when melatonin was added to protected plants from herbicide oxidation.

The greenhouse experiment highlighted the ability of melatonin, 24-Epibrassinolide and AsA to reduce bentazon and mesotrione injury in ‘Beauregard’ and ‘Covington’ sweetpotato. Beauregard treated with bentazon and mesotrione had injuries levels of 63% and 76%, respectively. Tank-mixing herbicides with melatonin had 7% and 48% less injury compared to herbicides alone. Additionally, the compounds did not reduce control of yellow nutsedge from bentazon and control Palmer amaranth (Amaranthus palmeri L.) from mesotrione.

In field trials tank mixing bentazon with plant hormones was evaluated. At both locations, bentazon + plant hormones resulted in 50% and 74% more yield of marketable roots than bentazon alone and the non-treated check, in Cameron and Charleston, respectively. For herbicide injury, bentazon applied alone reduced the final yield by 50% in Cameron and 79% in Charleston, compared to tank-mix of bentazon + plant hormones.

These studies suggest plant hormones and ascorbic acid reduce sweetpotato injury to POST mesotrione and bentazon applications. These compounds did not reduce yellow nutsedge and Palmer amaranth control.



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