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Weed management is a major challenge across a variety of agronomic and horticultural crop production systems. Palmer amaranth (Amaranthus palmeri S. Watson) is one of the most difficult weeds to control in various crops across the United States. Electrical weed management has potential to improve management of Palmer amaranth in systems with and without preemergence herbicides; thus, studies were conducted to evaluate the efficacy of electrical weed management application schedules in sweetpotato (Ipomoea batatas L.), peanut (Arachis hypogaea L.), cucumber (Cucumis sativus L.), and cotton (Gossypium hirsutum L.). Herbicide treatments included a preemergence herbicide or no herbicide. Application schedules included weekly, biweekly (every two weeks), and monthly applications, as well as weedy and weed-free checks. A similar trend in Palmer amaranth control was identified in sweetpotato, cucumber, and cotton, wherein biweekly applications did not result in different control compared to weekly applications. In peanut, application schedule did not result in differences in control. These results indicate that more frequent applications do not necessarily result in better weed control; biweekly applications and even monthly applications may provide the best weed control depending on the cropping system.
Cover cropping and reduced tillage systems are important cultural weed management tools. Timely cover crop termination can be challenging in systems without synthetic herbicides. Thus, studies were conducted to evaluate the efficacy of electrical weed control for sunn hemp (Crotalaria juncea L.) cover crop termination with and without roller crimping. Treatments consisted of no termination, electrical termination one-pass, electrical termination two-passes, roller crimping alone, and electrical termination one-pass followed by roller crimping. The electrical termination two-pass treatment was the most effective termination treatment compared to the nontreated check by 2 WAT for both visual percent kill and fresh mass.
Flumioxazin is an important and widely used preemergence herbicide in sweetpotato production in North Carolina; however, concern exists about the safety of flumioxazin for sweetpotato yield and quality under certain conditions such as rainfall before or after application; thus, studies were conducted to test the efficacy and safety of flumioxazin with various simulated rainfall treatments. Herbicide treatments consisted of no herbicide, flumioxazin at 107 g ha-1 and 214 g ha-1 . Simulated rainfall treatments consisted of water applied before flumioxazin application, water applied after flumioxazin application, and no water applied. No visual injury from herbicide or rainfall treatments was observed. Flumioxazin at 214 g ha-1 reduced sweetpotato yield compared to the no herbicide treatment. However, flumioxazin at 107 g ha-1 (registered rate) did not reduce yield compared to the no herbicide treatment. No interactions between irrigation timing and herbicide were observed. The results of this study highlight both the safety of flumioxazin when applied at registered rates as well as the importance of appropriate application procedures to ensure that overapplication of flumioxazin does not occur.
The use of crop competition with weeds as a weed management tool has potential to improve sweetpotato weed management. Field studies were conducted in a full factorial splitsplit plot arrangement; The treatments consisted of in-row spacing, cultivar and competitive environment. In-row spacing treatments included 20 cm, 30 cm, and 40 cm. Cultivar treatments included ‘Covington’ and ‘Monaco’. Competitive environment treatments weedy and weed-free environments. While competitive environment affected both no. 1 and total sweetpotato yields across years, cultivars, and spacings, the only differences observed between spacings and environment were detected for no. 1 yield per plant in 2023. The lack of observed interactions between cultivar and competitive environment indicates that selected cultivars did exhibit differential tolerance to weed competition. Thus, there is no evidence that selected spacings or cultivars give a competitive advantage under weedy conditions.