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  • Author or Editor: Matthew Cutulle x
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Poor competitive ability and limited herbicide options make weed management of Brassica crops difficult. Growers often adopt the use of transplants, which is less efficient in terms of time, material, and labor when compared with direct seeding, resulting in higher prices per unit. Seed treatment with protective compounds could decrease crop injury from preemergent (PRE) herbicides making it profitable to direct-seed Brassica plants for production. Research was conducted to evaluate the ability of three candidate safeners [24-epibrassinolide, melatonin, and ascorbic acid (AsA)] to reduce injury caused by four herbicides (S-metolachlor, pyroxasulfone, halosulfuron, and mesotrione) applied PRE on the collard green cultivar Top Bunch and turnip cultivar Purple Top White Globe. Two independent greenhouse trials were conducted at the Clemson University Coastal Research and Education Center in Charleston, SC. Visual injury of the treated plants was evaluated weekly and dry mass was collected 21 days after treatment. Seed treatment did not reduce injury efficiently caused by pyroxasulfone, halosulfuron, and mesotrione; all doses were lethal for both crops. However, collard seeds treated using melatonin and AsA had 66% and 54% less injury caused by S-metolachlor at 514 g⋅ha–1 a.i., respectively. On turnips, melatonin was the only treatment that reduced the S-metolachlor damage on seedlings, with 43% less injury than untreated seedlings. Plant injury and plant weight correlated significantly for both Brassica crops. The reduction in injury caused by S-metolachlor when seeds were treated with melatonin and AsA validated those compounds’ protective ability. Seed treatment with melatonin could be combined with PRE applications of S-metolachlor to overcome the low weed competitive ability of these species early in the season.

Open Access

Increasing regulations and restrictions regarding on-farm chemical use and growing consumer demands for organic food products warrant the development of efficient biological methods for plant disease control and pest management. Grafting and anaerobic soil disinfestation are two sustainable crop production techniques developed to control and regulate weeds, root-knot nematodes (Meloidogyne incognita), and soilborne pathogens. Therefore, the present study explores the economic impact of using grafting and anaerobic soil disinfestation, independently and in conjunction, to determine the best combination in terms of yield and net returns for producers. This study drew from tomato (Solanum lycopersicum) field trials conducted in 2020 on a 0.5-acre plot at the Clemson Coastal Research and Education Center in Charleston, SC, where five grafting and three anaerobic soil disinfestation treatments were used in combinations for comparisons. Each treatment combination was subjected to sealed (plastic mulch covering a plot punctured 5 weeks after applying anaerobic soil disinfestation treatment) and unsealed (plastic mulch covering a plot punctured immediately after the application of anaerobic soil disinfestation treatment) plot conditions during the anaerobic soil disinfestation phase of plant bed preparation. Treatment combinations with cottonseed meal carbon-sourced anaerobic soil disinfestation were unviable because of lower net returns compared with treatment combinations without anaerobic soil disinfestation in nearly every case. Grafting (‘Roadster’ self-grafted) combined with molasses and chicken manure carbon-sourced anaerobic soil disinfestation under unsealed plot conditions was the most optimal treatment combination in the field trials with the greatest gains (net return per acre) to producers. The positive synergistic effects of combining these methods suggest that grafting and anaerobic soil disinfestation yield better results in conjunction than separately.

Open Access

Tall fescue (Festuca arundinacea) and hybrid bluegrass (Poa pratensis L. × Poa arachnifera) can both be successfully grown in the transition zone of the United States. However, each grass has limitations. Tall fescue is susceptible to the fungal pathogen Rhizoctonia solani, whereas slow establishment and susceptibility to weed infestations limit hybrid bluegrass. Previous studies have shown the benefits of combining kentucky bluegrass with tall fescue in seeding mixtures. Research was conducted to evaluate the impact of two seeding combinations of hybrid bluegrass and tall fescue (one combination seeded at a 1.9:1 seed count ratio favoring tall fescue, the other combination seeded at a 1:1.8 seed count ratio favoring hybrid bluegrass) as well as monocultures of the species on turfgrass cover, weed species infestation, brown patch disease severity caused by R. solani, sod strength and species ecology. The seeding combinations had lower weed density during establishment and greater turf cover than the monoculture of hybrid bluegrass. The monoculture of tall fescue was subjected to more brown patch disease than the seeding combinations during and after the first year of establishment. Brown patch infestations likely reduced tall fescue cover and led to a species shift favoring hybrid bluegrass in the seeding combinations based on tiller count and weight data. Seeding combinations of tall fescue and hybrid bluegrass are beneficial from an epidemiological perspective because they reduce disease and weed infestations compared with monocultures of either species. From an agronomic perspective, the seeding combination favoring tall fescue provided the densest turf, whereas the seeding combination favoring hybrid had the greatest sod strength. Chemical name used: clopyralid (3,6 dichloropyridine-2 carboxylic acid)

Free access

Anaerobic soil disinfestation (ASD) is a preplant pest management technique that involves amending the soil with a labile carbon source, irrigating the soil to stimulate decomposition, and then covering the soil with polyethylene film (polyfilm) to limit gas exchange. During the ASD process, soil microorganisms shift from aerobic to anaerobic metabolism and release phytotoxic byproducts such as organic acids and gases. Although it has been shown that these phytotoxic by-products have a negative impact on weed survival, questions remain about whether commercial-level weed control can be achieved using ASD alone or in combination with other chemicals. Greenhouse and field studies were conducted to evaluate ASD with mustard (Brassica sp.) meal, molasses, and herbicide applications for yellow nutsedge (Cyperus esculentus) control in tomato (Solanum lycopersicum). The treatments in these studies included factorial of two carbon sources [mustard meal + molasses (MMM) or no carbon amendment], three herbicide treatments [halosulfuron applied preemergence (PRE), halosulfuron applied postemergence (POST), and no herbicide] and two polyfilm treatments (polyfilm cover or polyfilm uncover). In field trials two polyfilm cover treatments were punctured and nonpunctured. Soil treatments included molasses at 14,000 L·ha−1 and mustard meal at 2100 kg·ha−1. Halosulfuron was applied at a rate of 1 oz/acre for PRE or POST applications. Greater anaerobic conditions were achieved in polyfilm cover treatments amended with MMM. In greenhouse and field trials, the most effective treatments for reducing yellow nutsedge populations were ASD with MMM or combined with halosulfuron application (PRE- or POST-ASD), which delivered significantly higher weed control than all other treatments tested or controls. In field trials, ASD with MMM caused plant growth stunting 14 d after transplantation (DAT); however, plants recovered, and stunting or injury was often not observed at 42 DAT. These studies demonstrated that ASD using MMM can be an effective strategy for reducing yellow nutsedge populations; however, the more research is needed to ensure crop safety while using ASD technology.

Open Access

Weed management is an important component of sweetpotato production. Currently, S-metolachlor is the only herbicide registered in sweetpotato that has some suppressive effect on nutsedge species (Cyperus spp.). It is integral that the release of any new germplasm from sweetpotato breeding programs be tolerant to S-metolachlor. Screening for thousands of experimental clones for S-metolachlor in a field trial would be cumbersome. Therefore, screening for tolerant lines might be streamlined in an hydroponics system. Research was conducted to determine whether a hydroponics assay could detect differences in S-metolachlor response between a known sensitive sweetpotato cultivar (Centennial) and a tolerant sweetpotato cultivar (Beauregard) in 10 days. Results of the study show that ‘Beauregard’ was ≈50 times more tolerant to S-metolachlor than ‘Centennial’ when accessing injury at the 25% threshold. No differences were detected in S-metolachlor response between cultivars in the soil-based assay. This assay could be used for screening for S-metolachlor tolerance in a sweetpotato breeding program.

Open Access

Weed competition is a main factor limiting sweetpotato [Ipomoea batatas (L.) Lam] production. Yellow nutsedge (Cyperus esculentus L.) is a problematic weed to control due to its ability to quickly infest a field and generate high numbers of tubes and shoots. Compounding this is the lack of a registered herbicide for selective postemergence control of yellow nutsedge. Research was conducted to evaluate the bentazon dose response of two sweetpotato cultivars and one advanced clone and to evaluate the plant hormone melatonin to determine its ability to safen bentazon post emergence. Bioassays using Murashige and Skoog (MS) media supplemented with melatonin (0.232 g a.i./L and 0.023 g a.i./L) and bentazon (0.24 g a.i./L) were conducted to evaluate the effect of bentazon on sweetpotato and to determine the interactive response of the Beauregard cultivar to bentazon and exogenous applications of melatonin. Beauregard swas the most tolerant cultivar and required dosages of bentazon that were two-times higher to cause the same injury compared with other cultivars. MS media containing melatonin and bentazon showed fewer injuries and higher plant mass than plants treated with bentazon alone. These results indicate that sweetpotato injury caused by bentazon may be reduced by melatonin.

Open Access

Goosegrass (Eleusine indica L. Gaertn.) is a problematic C4 weedy grass species, occurring in the warmer regions of the world where it is difficult to selectively control without injuring the turfgrass. Furthermore, control efficacy is affected by plant maturity. End-user options for satisfactory goosegrass control has decreased; thus, the need for developing management techniques to improve the selectivity of POST goosegrass control options in turfgrass systems is ever increasing. One possible means of providing control, yet maintaining turf quality is immediately incorporating applied products via irrigation. Greenhouse and field trials were conducted in Pickens County, SC, with the objectives of 1) evaluating turfgrass injury following use of POST goosegrass control options; 2) assessing if irrigating (0.6 cm) immediately following the herbicide application reduces injury of ‘Tifway 419’ bermudagrass [Cynodon dactylon (L.) Pers. × Cynodon transvaalensis Burtt-Davy]; and 3) determining if immediate irrigation influences goosegrass control at one- to three-tiller and mature growth stage. Following the application of herbicide treatments, irrigation was applied (+) or not applied (−). Treatments included the following: control (+/− irrigation); topramezone at 12.3 g a.i./ha (+/− irrigation); metribuzin at 420 g a.i./ha (+/− irrigation); and topramezone plus metribuzin (+/− irrigation) at 12.3 and 420 g a.i./ha. Irrigation treatment had minimum effect on greenhouse-grown goosegrass biomass, all treatments provided >85% control of 1- to 3-tiller goosegrass plants. However, control for mature plants was <50% for topramezone- and 60% to 70% for metribuzin-containing treatments. In field studies, at 1 week after treatment (WAT), the irrigated metribuzin and topramezone plus metribuzin had ≈37% and ≈16%, respectively, less goosegrass control vs. nonirrigated treatments. At 2WAT, irrigated metribuzin and irrigated topramezone plus metribuzin–treated plots, had ≈50% less mature goosegrass control vs. nonirrigated treatments. Irrigated herbicide treatments, however, experienced ≈23% less turfgrass injury at this time. At 4 WAT, irrigated metribuzin- and irrigated topramezone plus metribuzin–treated plots experienced reduced mature goosegrass control by ≈65% and ≈59%, respectively. Overall, incorporating POST herbicide applications via 0.6 cm of irrigation reduced turfgrass injury by at least 20% for all herbicide treatments, while maintaining goosegrass control.

Free access

A greenhouse trial was used to evaluate 159 accessions of bottle gourd [Lagenaria siceraria (Mol.) Standl.] obtained from the U.S. National Plant Germplasm for tolerance to clomazone herbicide. Most accessions tested were moderately or severely injured by clomazone at 3.0 mg·kg−1 incorporated into greenhouse potting medium; however, several exhibited lower injury. Seeds were produced from tolerant and susceptible plants for use in a greenhouse concentration–response experiment. About three to four times higher clomazone concentrations were required to cause moderate injury to tolerant bottle genotypes in comparison with susceptible genotypes. The differences in tolerance among genotypes were observed with injury ratings, chlorophyll measurements, and shoot weights. Clomazone may be used safely on tolerant bottle gourd genotypes, but the herbicide may not be safe for susceptible genotypes. Also, tolerant genotypes such as Grif 11942 may be desirable for use as rootstocks in grafted watermelon production.

Free access

Increased broccoli production in the eastern United States necessitates the exploration of novel concepts to improve weed management in this region. Currently, there are minimal selective postemergent herbicide options available for broccoli growers in the southeastern United States. Research was conducted to determine if bentazon, an effective nutsedge herbicide, could be used safely for broccoli when tank-mixed with chelated iron in both greenhouse and field settings. Initial greenhouse screens in Charleston, SC, demonstrated that when 224 g⋅ha−1 active ingredient of chelated iron was tank-mixed with bentazon, a reduction in injury occurred in most of the cultivars that were evaluated. However, based on injury ratings, yield parameters, and broccoli quality observed in the field, it appears that the applications of chelated iron yielded no positive effects. Furthermore, for some of the broccoli cultivars it appeared to exacerbate bentazon injury in the field.

Open Access

Root traits are an important component for productive plant performance. Roots offer immediate absorptive surfaces for water and nutrient acquisition and are thus critical to crop growth and response to biotic and abiotic stresses. In addition, roots can provide the first line of defense against soilborne pathogens. Watermelon crop performance is often challenged by inclement weather and environmental factors. A resilient root system can support the watermelon crop’s performance across a diverse range of production conditions. In this study, 335 four-day-old watermelon (Citrullus spp.) seedlings were evaluated for total root length, average root diameter, total root surface area, and total root volume. Total root length varied from 8.78 to 181 cm (20.6-fold variation), total surface area varied from 2 to 35.5 cm2, and average root diameter and total root volume had an 8- and 29.5-fold variation, respectively. Genotypes PI 195927 (Citrullus colocynthis) and PI 674448 (Citrullus amarus) had the largest total root length values. Accessions PI 674448 and PI 494817 (C. amarus) had the largest total root surface area means. Watermelon cultivars (Citrullus lanatus) had a relatively smaller root system and significantly fewer fibrous roots when compared with the roots of the other Citrullus spp. Positive genetic correlations were identified among total root length, total root surface area, and total root volume. This genetic information will be useful in future breeding efforts to select for multiple root architecture traits in watermelon. Germplasm identified in this study that exhibit superior root traits can be used as parental choices to improve watermelon for root traits.

Open Access