Prickly Sida ( Sida spinosa L.), Hemp Sesbania [ Sesbania herbacea (Mill.) McVaugh], and Pitted Morningglory ( Ipomoea lacunose L.) Response to Selective and Non-Selective Herbicide in Mississippi, USA

Prickly sida ( Sida spinosa ), hemp sesbania ( Sesbania herbacea ), and pitted morningglory ( Ipomoea lacunose ) are becoming problematic weeds in many crops including corn and soybean. Two separate field experiments, under non-crop conditions, were conducted at the Mississippi State University Delta Research and Extension Center, in Stoneville, MS to evaluate the response of these weeds to eight corn selective herbicides and three non-selective herbicides alone or in combination. The herbicides used were Aatrex (atrazine), Clarity (dicamba), 2,4-D (2,4-D amine), Callisto (mesotrione), Enlist Duo (2,4-D choline + dicamba), Capreno (thiencarbazone + tembotrione), Corvus (thiencarbazone + isoxaflutole), Halex GT (mesotrione + S -metolachlor + glyphosate), Gramoxone (paraquat), Liberty (glufosinate), and Roundup (glyphosate). Halex GT provided only 86% prickly side control 4-wks after application (WAA). Aatrex + Capreno and Aatrex + Corvus were the only treatments provided 99.5% prickly sida control. Liberty, Callisto, Capreno, and Corvus provided 71, 66, and 51, and 46% control of prickly sida, respectively. Hemp sesbania control was 100% from all herbicide applications except Corvus and Roundup. Hemp sesbania control was not satisfactory from Roundup application since this treatment provided only 72% control. By 4 WAA, all herbicide treatments provided 97 to 100% on pitted morningglory control except Corvus and Capreno treatments (72 to 75%). The herbicide management program should be able to provide acceptable weed control ( i.e. , greater than 95%) but also to prevent weed seed deposition onto the soil seedbank. Consequently, delaying the evolution of weed herbicide resistance will result in herbicide technology preservation for as long as possible by achieving a long-term weed management program.


Introduction
Prickly sida (Sida spinosa L.) has become a particularly problematic weed for agronomic cropping systems in the Mid-South region of the United States, especially in cotton (Gossypium hirsutum L.), soybean (Glycine max L.), corn (Zea mays L.), and peanut (Arachis hypogaea L.) (Korres et al., 2015a(Korres et al., , 2015b(Korres et al., , 2017;;Webster & Nichols, 2012).The credence of chemical herbicides to control this troublesome weed has decreased with its usage (Webster & Nichols, 2012;Copes et al., 2021).This bothersome weed reduces yields in many crops including soybean (Webster & Nichols, 2012).It has been documented mentioned that prickly sida caused soybean yield reduction by 9-14% (Jeffery et al., 1976).The control of this weed species is difficult, especially in agronomic fields, due to its ability to emerge throughout the growing season, to thrive under crop canopy with reduced light, and its great capacity for seed production after the crop has been harvested (Copes et al., 2021).Currently, the most popular method to control prickly sida is by using chemical herbicides.Field research conducted in 2014 at two locations in Arkansas reported the effectiveness of several herbicide programs in edamame (Salas et al., 2014).According to recent research in Mississippi, USA, a 2 to 3 applications of a wide herbicide programs range was efficient in controlling prickly sida populations in cotton fields (Ferguson et al., 2022).Application timing may be an important factor when applying herbicides to burndown prickly sida populations.In a soybean field study, it was found that late-season control of prickly sida was 93% with herbicide application at-planting and postemergence without the inclusion of any residual herbicide (Copes et al., 2021).In a study on preemergence herbicides and spray nozzle types found that the efficacy of imazethapyr in prickly sida increases under high residue levels (Ferguson et al., 2022).
Pitted morningglory (Ipomoea lacunose) is a twining annual vine with ovate leaves, pubescent capsules, and white corolla (Radford et al., 1968), and under non-competitive conditions, it can produce up to 15,000 seeds per plant (Senseman & Oliver, 1993;Norsworthy & Oliver, 2002a).Morningglories, mainly pitted morningglory, are one of the most problematic broadleaf weeds in the southeastern and southern Midwest USA (Korres et al., 2015a(Korres et al., , 2015b;;Dowler, 1995;Uva et al., 1997).These weeds are primarily found in agricultural areas, woodland margins, and roadsides (Korres et al., 2017;Korres et al., 2015aKorres et al., , 2015b;;SWSS, 1998).Pitted morningglory is one of the most dominant morningglory species in the Mississippi Delta region (Korres et al., 2015a;Elmore et al., 1982).In crops like corn, cotton, and soybean, it is the second most problematic weed in Mississippi (Webster, 2001) and is among the glyphosate-tolerant weeds (Taylor, 1996).As mentioned by Jordan et al. (1997) morningglories were less effectively controlled by glyphosate compared to other species.Among these species, pitted and entire leaf morningglory were reported to be more glyphosate-tolerant than smallflower and palmleaf morningglory (Norsworthy & Oliver, 2002), hence are becoming more problematic weeds in glyphosate-resistant crops such as soybean and cotton (Chachalis et al., 2000).Mesotrione when used alone showed 51% control in pitted morningglory while when it was used with glyphosate pitted morningglory control increased to 65% (Armel et al., 2003).According to a study by Johnson et al. (2002), a mixture of mesotrione and atrazine was required for effective control of morningglory species as mesotrione alone failed to provide adequate control.Due to its prolific seed production and multiple germination timings, season-long control of pitted morningglory under favorable environmental conditions may not be attained with soil-applied herbicides alone.For example, imazapyr alone at a 7g/ha rate didn't affect pitted morningglory growth and development (Riley & Shaw, 1998).
Hemp sesbania (Sesbania herbacea) is an aggressive annual weed that poses threats to rice (Oryza sativa L.), corn, cotton, and sunflower (Helianthus annuus L.) (Woon, 1987).It commonly grows on uncultivated fields in Mississippi, Arkansas, and Louisiana (Korres et al., 2015a(Korres et al., , 2015b) ) and is very difficult to control (Dowler, 1992).In addition to being prolific (i.e., it produces 21,000 seeds per plant) (Lovelace & Oliver, 2000), it can also grow up to three meters high at maturity (Lorenzi & Jeffery, 1987).Its shading and competitive abilities enable it to reduce crop yields (Norsworthy & Oliver, 2002b;King & Parcell, 1997).Hemp sesbania is known to cause extensive damage to combine blades during crop harvest (Domsch et al., 1980).Leaf and stem compounds found in hemp sesbania are toxic to humans and livestock, with the seeds as the most lethal part of the plant (Everest et al., 1996).The most commonly methods of controlling hemp sesbania in most crops is by a single or multiple herbicide application (Lovelace & Oliver, 2000).Herbicides such as acifluorfen and fomesafen have effectively controlled hemp sesbania (Shaw & Amold, 2002).In soybeans, for example, the minimum effective rates of acifluorfen or fomesafen to suppress 50-to 60-cm tall hemp sesbania were 50 and 140 g ha -1 , respectively (Vidrine et al., 1992).Glyphosate combined with acifluorfen and chlorimuron was reported to reduce hemp sesbania fresh weight by almost half in soybean (Norris et al., 2011).Despite the efficacy of herbicides in controlling this weed, it has demonstrated resistance to glyphosate that makes the weed species a significant problem for farmers (Jordan et al., 1997;Norris et al., 2001).Single applications of glyphosate could not adequately control hemp sesbania (Johnson & Young, 2000;Lorenzi & Jeffery, 1987).There is, therefore, a need for additional control options.
The objective of this study is to evaluate a range of selective and non-selective herbicides that are usually used in Mississippi corn for the control of prickly sida, hemp sesbania, and pitted morningglory.

Field Experiments and Herbicide Treatments
Field studies were conducted in 2020 at the Mississippi State University Delta Research and Extension Center in Stoneville, MS on Sharkey clay (very fine, smectitic, thermic Chromic Epiaquerts) with 2.4% organic matter and pH 7.5.The experimental design was a randomized complete block with three replications.Herbicide treatments were involved eight sites of actions within 13 herbicide treatments.The trade names, site of action, chemical group, manufacturer information and application rates for the herbicides used in this study are listed in Table 1.A non-treated control was also included in the study.The experiment was repeated twice (two runs).Herbicide treatments were applied on July 1 on 3-to 6-leaf prickly sida, 5-to 7-leaf hemp sesbania, and 2-to 4-leaf pitted morningglory.Experiment was conducted on a natural population of prickly sida, hemp sesbania, and pitted morningglory under non-crop conditions.Herbicide applications were made using a CO 2 -pressurized backpack sprayer calibrated to deliver 141 L ha -1 at 276 kPa.The boom consisted of 51-cm nozzle spacing equipped with Turbo TeeJet (TeeJet Technologies, Springfield, IL) Induction (TTI) 110015 nozzles.Prior to the experiment, a conventional seedbed was prepared by moldboard plowing and tandem disking twice in early April and prickly sida, hemp sesbania and pitted morningglory was allowed to establish a uniform natural population with an average density 97, 2 and 3 plants m -2 , respectively.Plot size was 4-m wide and 6-m long.

Assessment of Herbicide Efficacy and Data Analysis
Visual injury assessments for all weed species were based on 0 to 100% scale relative to the nontreated plots.Zero percentage (0%) indicated no control and 100% being complete plant death.The efficacy of herbicides on these weeds was evaluated weekly from 1 to 4 weeks after herbicide application (WAA).Weekly assessments were analyzed separately using the GlimMix procedure by SAS statistical software (SAS Institute Inc., Cary, NC).Prior to analysis, all data was examined for normality using the univariate procedure in SAS.In addition, the homogeneity of variance was tested with Bartlett's test.The herbicide treatments were considered fixed effects, whereas treatment replication was considered as random.No run (two separate field studies translates to two runs of the experiment) effects were observed, hence data from each run were combined prior to data analysis.Means were separated by t-test at significance level α = 0.05.Note.*, ** = based on Weed Science Society of America; † = plus induce (nonionic surfactant).

Prickly Sida Control
One-week after application (WAA) Aatrex + Corvus and Aatrex + Capreno were the most effective herbicide treatments that provided 99% control of prickly sida (Figure 1).Non-selective herbicides Paraquat and Liberty provided 90 and 93% prickly sida control respectively whereas the percentage control of Roundup PowerMax, Enlist Duo, and Aaartex alone ranged between 80 to 82%.Halex GT, Clarity and 2,4-D provided 72%, 73% and 65% prickly sida control respectively (Figure 1).The lowest percentages of prickly sida control (< 50%) were obtained under Callisto, Corvus, and Capreno treatments (< 50%) (Figure 1).Herbicide activity, as anticipated, increased over time.Two WAA Roundup PowerMax application increased prickly sida control by 17% whereas the percentage control of Aatrex + Corvus, and Aatrex + Capreno remained at the same level as that recorded one WAA (Figure 1).In addition, Aartex and Enlist Duo were also provided high prickly sida control (89 to 91% respectively).However, the effectiveness of Aatrex, Halex GT, Liberty, and Clarity compared with that obtained

Table 1 .
Herbicide treatments for the control of prickly sida, hemp sesbania and pitted morningglory used in this study