Bronze wilt was an issue for the cotton industry in the 1990s but mentions of bronze wilt in the literature were minimal until cotton leafroll dwarf virus (CLRDV) was observed across the cotton belt beginning in 2017. In 2024, bronze wilt symptoms were observed at high levels in Southwest Georgia. University of Georgia on-farm cotton variety trials (10 varieties evaluated across 19 locations) were used to quantify susceptibility to expression of bronze wilt symptoms and impacts on lint yield. Overall, the four varieties evaluated were determined to express bronze wilt symptoms; an additional variety outside the trial program was determined to be susceptible based on observations in grower fields. Differences in symptom severity were observed among locations, with some showing significant yield impacts, whereas others were unaffected. Averaged across non-yield-limiting locations (14 out of 19), 2 to 3% symptomatic plants were observed in symptomatic varieties: symptoms increased to 28 to 35% averaged across yield-limiting locations (5 out of 19). Where yield was affected, bronze wilt symptoms reduced lint yield 16 to 32% in the four susceptible varieties. Across all locations, a negative linear relationship was observed within susceptible varieties: a 1% increase in symptoms resulted in a 0.54% decrease in relative lint yield. These data are the first from replicated research to document yield losses associated with bronze wilt symptoms. Future research should evaluate in-field variety screening methods, genetics of susceptibility to expression of bronze wilt symptoms, and controlled environment experiments to replicate symptoms.
Assessments from the U.S. Environmental Protection Agency suggest that some insecticides can be affected by usage restrictions or label vacatur in the future. An experiment was conducted in Stoneville, Sidon, and Glendora, MS during 2023 to determine the effects of excluding insecticide classes for the control of the tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), on DP 2131 B3TXF ThryvOn cotton and DP 1646 B2XF cotton. Treatments were replicated in both the ThryvOn and non-ThryvOn varieties and included a season-long untreated control, all classes available for use, all classes except neonicotinoids, all classes except pyrethroids, all classes except organophosphates, and all classes except sulfoximines. Plots were scouted weekly to monitor tarnished plant bug densities and applications were made to plots independently using the best available insecticide options when each treatment reached established plant bug thresholds. Results indicated no significant differences in yield among exclusion class treatments in either variety. Significant reductions in yield were observed in the untreated control plots compared to plots that received insecticide intervention in both the ThryvOn and non-ThryvOn technologies. However, there were no significant differences between the economic returns of the untreated control plots compared to the plots receiving insecticide intervention in the ThryvOn technology. This evidence suggests that if insecticide usage is restricted from a single class, comparable yields can be achieved. However, it should be noted that any loss or reduction in insecticide usage currently used for tarnished plant bug control would result in increased selection pressure on the remaining insecticides, ultimately increasing resistance to those classes that remain available.
Experiments were conducted at the Delta Research and Extension Center in Stoneville, MS during 2022 and 2023 to investigate the impact of irrigation and simulated late-season damage of tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), in cotton. The whole-plot factor compared a 90-centibar irrigation threshold and a non-irrigated treatment. Subplot factor A involved simulated damage by manual removal of squares during the fourth and fifth week of bloom. Three levels of damage at 0, 50, and 100% removal of squares above the uppermost first position white flower was subplot factor B. To understand agronomic impacts and compensation, plant heights, total node counts, nodes above white flower (NAWF), and nodes above cracked boll measurements were recorded beginning at the first week of bloom. Yield was also recorded from each plot. Results from 2022 and 2023 showed significant increases in NAWF from 100% fruit removal during both removal weeks compared to all other removal treatments; however, all treatments remained below five NAWF. No significant yield differences were found among any factor except irrigation. Threshold irrigated cotton had significantly greater yields than non-irrigated cotton. Results from this experiment agree with previous research suggesting insecticide termination could occur after the fourth week of bloom with minimal impacts to plant maturity and yield in both irrigated and non-irrigated situations.
Cotton leafroll dwarf virus (CLRDV) is an aphid-transmitted virus recently identified across the Cotton Belt region of the U.S. Yield responses to CLRDV have been inconsistent, and asymptomatic infections can occur in which no losses are apparent. Conditions underlying the observed variation in yield responses are not understood. A three-year field study was conducted to examine whether yield loss caused by CLRDV is influenced by the age of cotton plants at the time of infection. Timing of infection was investigated by infesting caged plots of cotton with viruliferous Aphis gossypii to transmit CLRDV at different seedling growth stages, beginning after seedling emergence and continuing weekly for three to four weeks. Timing of infection impacted yield only in one out of three years suggesting that plant age is not a primary factor contributing to CLRDV-related yield loss. Future studies are needed to identify the environmental factors influencing disease severity and yield loss.
Increased lint yield of cotton (Gossypium hirsutum L.) cultivars is the primary objective of most cotton breeding programs. Partitioning lint yield into yield components can provide the opportunity to improve lint yield by indirect selection. Lint yield can be defined as the product of lint index (LI) and number of seed per area (SPA). A subjective yield-component rating (YC1) of relative ranks of LI and SPA in University of Arkansas (UA) strain tests has been used to identify lines that have favorable relationships of LI and SPA. An objective, computer-generated application, yield component score (YC-score), available to identify these lines. We were able to generate four years of YC-scores for the 67 UA lines released since 2007. High correlations between YC-score and YC1 indicated that YC-score captured the intent of the YC1 ratings. YC-scores of the 67 released lines were relatively consistent over years of testing and varied greatly among the lines. YC-score was calculated for entries in eight Regional Breeders' Testing Network (RBTN) tests and correlated with lint yield and other yield component variables. YC-score varied among entries in each RBTN test. Correlations with YC-score were highest for LI, SPA, fibers per seed, S-score, and seed index. Negative correlations between YC-score and lint yield in all eight RBTN tests indicate that it should not be used as a primary selection tool. Among high performing cultivars, YC-score can differentiate those that have the most favorable yield component values.
Leafhoppers (Cicadellidae) are major pests of key crops, including okra, eggplant, and cotton, in tropical Africa. Several closely related species, which are often challenging to differentiate, infest these crops, yet little is known about their relative roles in causing crop damage. The study aims to clarify the taxonomy of the species and provide a preliminary assessment of their impact on eggplant, okra, and cotton production. A biomolecular analysis was conducted on 180 leafhopper individuals collected from 13 locations across the three crops during the 2021 and 2022 cropping seasons. The findings revealed that the same species were present on cotton, okra, and eggplant. Three primary species were identified: Empoasca papayae, Jacobiasca lybica, and Amrasca biguttula. The abundance of these species varied between the two years. In 2021, the predominant species found on okra, eggplant, and cotton were J. lybica and E. papayae; J. lybica was the most abundant, proportions on okra, eggplant, and cotton were 90, 95.8, and 91.7%, respectively. In contrast, by 2022, A. biguttula emerged as the most abundant species with proportions of 100, 100, and 85% on okra, eggplant, and cotton, respectively. Although J. lybica was present on cotton, it was less abundant. The introduction of A. biguttula, a species new to West Africa, marked a shift in the leafhopper community, replacing the local species on African eggplant, okra, and cotton. These results enhance our understanding of leafhopper species composition on these important crops and will inform the development of targeted pest management.
The cotton (Gossypium hirsutum L.) cool germination test is conducted to provide information regarding how seed lots will likely perform in suboptimal conditions. One aspect of the cool germination test is the use of a 4-cm radicle length threshold for a seedling to be counted as germinated, with little data to support its use. The objective of this study was to correlate cool germination test results using different radicle length thresholds with in-field emergence parameters. Germination tests were conducted to determine cool germination percentages for 12 seed lots using various radicle length thresholds. Field trials consisting of 12 seed lots were used to determine in-field emergence and vigor under suboptimal conditions. Linear regression was used to generate R-2 values between the percentage cool germination using various radicle length thresholds and in-field emergence parameters. These R-2 values were used to compare how well different radicle length thresholds explained variation in emergence and seedling vigor data. Across site-years and in-field parameters the radicle length threshold that maximized R-2 was under 3 cm, with variation between parameters and field sites observed. The 4-cm radicle length threshold used commercially in cool germination testing did not maximize R-2 value at any location for any field data collected. These results suggest that using a shorter radicle length threshold than the 4-cm standard when conducting the cool germination procedure would improve predictability of a seed lot's performance in field conditions that are suboptimally cool.
The threecornered alfalfa hopper (TCAH), Spissistilus festinus (Say), is a sporadic pest in seedling cotton that has the potential to cause significant impact to cotton growth and development. Threecornered alfalfa hopper is a stem girdling pest that generally feeds on the main stem of cotton plants from the two-to eight-leaf growth stages. To better understand the potential impact of this pest on cotton growth and development, trials were conducted in Starkville and Stoneville, MS in 2023 and 2024. Experiments were implemented as a randomized complete block design with a factorial arrangement of treatments with four replications. Factor Awas simulated TCAH damage at 0, 10, 20, 30, 40, and 50% increments; factor B was damage timed at the three-and six-leaf growth stage. Damage was simulated by applying low rates of glyphosate to stunt the plant to approximate TCAH damage. There were no significant impacts of simulated TCAH damage level percentage or timing on yield. Therefore, the results from this study suggest that TCAH has little economic impact on cotton seedlings.
The threecornered alfalfa hopper (TCAH), Spissistilus festinus (Say), is a stem girdling insect pest that has the potential to injure seedling cotton resulting in stunted growth and discoloration. During 2023 and 2024, 120 field surveys were conducted across eight cotton producing counties in the Mississippi Hills region to identify environments favorable for TCAH damage, as well as quantify the amount of damage observed. Field characteristics such as weed presence, tillage practice, and environments bordering the field were recorded along with cotton growth stage. The number of damaged plants out of 100 plants was recorded at 0, 4, 8, 15, 30, and 45 m into the field to determine damage distribution. Higher amounts of TCAH damage were associated with fields that implemented no-tillage cultivation systems and had high populations of weeds along field edges. Damage was more prevalent at 0 m and decreased further into the field; confirming that this is an issue predominantly along field edges. From these results, the implementation of cultural practices such as conventional tillage and minimizing weedy field edges could lessen the effects of TCAH damage on cotton, thus limiting the need for chemical control.
Tarnished plant bug (TPB) (Lygus lineolaris Palisot de Beauvois; Hemiptera: Miridae), is the number one insect pest in U.S. Mid-South crops including cotton. Development and deployment of lines exhibiting partial resistance to TPB could reduce the quantity of insecticides needed to control this pest. We have evaluated TPB resistance of cotton lines in small plots since 2003. Insecticides were not applied for TPB. When TPB damage was readily seen in flowers of the susceptible check, examination for "dirty flowers" was made on six white flowers per day for 5 to 8 days. Cumulative percent dirty flowers over sampling days was then calculated for each plot. Over the last 21 years, we evaluated 2,724 lines in 102 different tests. Variation between supposed resistant and susceptible check cultivars were relatively consistent over tests. These data were used to quantify the level of TPB resistance in breeding strains and in 90 germplasm lines and cultivars released from the University of Arkansas Cotton Breeding Program, as well as cultivars and breeding lines in the annual Arkansas Cotton Variety Test and Regional Breeders' Network Test. Over the years, nectariless and highly pubescent lines have consistently provided some TPB resistance. However, TPB resistance has been found in some nectaried and glabrous lines. These findings suggest the existence of different mechanisms for TPB resistance.
Cotton, Gossypium hirsutum (L.), is a vital crop across the southern U.S. Numerous insect species are yield-limiting pests throughout the cotton growing regions of the U.S., often requiring multiple foliar insecticide applications annually. Those insecticides pose an indirect risk to honey bees, Apis mellifera (L.), and other pollinators through contaminated nectar, pollen, or other routes during cotton bloom. Currently, pest managers only consider efficacy against the target pest when selecting insecticides and give little consideration to honey bee toxicity. The objective of this study was to incorporate honey bee acute toxicity data as a non-target insect pollinator and insecticide efficacy data against target pests into insecticide selection. Efficacy trials were conducted in mid-southern U.S. to determine the efficacy of eight and five currently recommended insecticides against tarnished plant bug (Lygus lineolaris [Palisot de Beauvois]) and bollworm (Helicoverpa zea [Boddie]), respectively. Insecticides were ranked based on historical published data for their toxicity to honey bees and efficacy against the targeted pest based on standardized trials across multiple states. The rankings were multiplied to give equal weight to honey bee toxicity and pest efficacy. Novaluron, sulfoxaflor, and flonicamid provided the best balance between efficacy against tarnished plant bug and acute toxicity to honey bees. Chlorantraniliprole provided the best balance between honey bee toxicity and bollworm efficacy. These findings can be used to improve integrated pest management strategies by maximizing control of pests while considering honey bee toxicity.
Bronze wilt was an issue for the cotton industry in the 1990s but mentions of bronze wilt in the literature were minimal until cotton leafroll dwarf virus (CLRDV) was observed across the cotton belt beginning in 2017. In 2024, bronze wilt symptoms were observed at high levels in farm cotton variety trials (10 varieties evaluated across 19 locations) were used to quantify susceptibility to expression of bronze wilt symptoms and impacts on lint yield. Overall, the four varieties evaluated were determined to express bronze wilt symptoms; an additional variety outside the trial program was determined to be susceptible based on observations in grower fields. Differences in symptom severity were observed among locations, with some showing significant yield impacts, whereas others were unaffected. Averaged across non-yield-limiting locations (14 out of 19), 2 to 3% symptomatic plants were observed in symptomatic varieties: symptoms increased to 28 to 35% averaged across yield-limiting locations (5 out of 19). Where yield was affected, bronze wilt symptoms reduced lint yield 16 to 32% in the four susceptible varieties. Across all locations, a susceptible varieties: a 1% increase in symptoms resulted in a 0.54% decrease in relative lint yield. replicate symptoms.
Root-knot nematode (Meloidogyne incognita) (RK) causes yield losses in cotton. Small-plot variety trials were conducted in the southern High Plains of Texas to evaluate RK density (2nd-stage juveniles + eggs/500 cm(3) soil) and cotton (Gos-sypium hirsutum) lint yield across commercially identified RK-resistant varieties. These varieties were compared to susceptible varieties (SUS) in nine trials over two years. Only a subset of resistant and SUS varieties was included in each location. Varieties that had consistently lower ( p = 0.05) transformed RK densities (LRK) compared to SUS were DP 2143NR B3XF (6 of 9 trials), DP 2141NR B3XF (3 of 6 trials), DP 2436NR B3TXF (2 of 5 trials), PHY 205 W3FE (2 of 4 trials), PHY 332 W3FE (3 of 4 trials), PHY 411 W3FE (2 of 3 trials), PHY 415 W3FE (2 of 3 trials), PHY 443 W3FE (3 of 4 trials), PHY 475 W3FE (3 of 4 trials), and PHY 480 W3FE (2 of 2 trials). In contrast, FM 765AX, FM 823AXTP, FM 868AXTP, and ST 6000AXTP did not exhibit reduced LRK densities relative to SUS in any trial. Varieties that had consistently higher ( p = 0.05) yield than SUS included FM 765AX (2 of 3 trials), PHY 475 W3FE (2 of 4 trials), and PHY 480 W3FE (1 of 2 trials). Cotton producers should consider both the level of resistance of a variety as well as yielding ability in a region when making variety choices for planting cotton in RK fields.
A split-split plot experiment was conducted in Stoneville, MS in 2022 and 2023 to establish more precise insect termination timing to reduce insecticide applications for tarnished plant bug during late bloom in cotton. The main-plot factor was cotton technology that included non-ThryvOn and ThryvOn cotton. The subplot factor was removal timing. In each year, manual removal of squares took place during the fourth or fifth week of bloom. The sub-subplot factor was level of square removal consisting of 0, 50, and 100% above the uppermost first position white flower. To understand plant growth, maturity measurements were taken beginning at the first week of bloom until defoliation. These measurements included plant height, total node counts, nodes above white flower, and nodes above cracked boll. Cotton yield was also recorded. Results from 2022 and 2023 showed differences in plant maturity when 100% square removal was done during the fourth week of bloom. Due to differences among varieties, ThryvOn cotton had greater yields than non-ThryvOn cotton. These data combined with previous research suggest that insecticide termination could occur after the fourth week of bloom without significant yield loss.
The use of lignocellulosic biomass to produce value-added chemicals like furfural, a platform chemical typically produced via acid-catalyzed dehydration of pentose sugars derived from hemicellulose, is gaining attention in the biorefinery industry. Cottonseed hulls (CSH), an abundant by-product of the cotton industry, represent a promising source for furfural production due to relatively higher hemicellulose content (11.6-24.5%) in comparison to hemicellulose content of other lignocellulosic biomasses such as wheat bran (22%), bagasse (16.52%), and hemp (10.60%). The objective of this study is to optimize the furfural production process using Box-Behnken design (BBD), a response surface methodology, to maximize furfural yield from CSH. The effects of three critical variables on furfural yield were systematically investigated: pre-treatment using varying ratios (5:1-15:1) of 1% H2SO4 to CSH (1% H2SO4:CSH); acid hydrolysis using varying concentration (2.5-7.5%) of H2SO4 to CSH (% H2SO4:CSH); and reaction time ranging from 30 to 90 min. Statistical analysis using ANOVA confirmed the model significance (p < 0.05) and revealed that all three variables (either individual or interaction) had significant effects on furfural yield. The optimized process conditions: pretreatment of 11.731 (1% H2SO4:CSH), acid hydrolysis of 6.74% (% H2SO4:CSH), and a reaction time of 81.2 min with desirability 1 resulted in a furfural yield of 14.34%. The study successfully demonstrates the application of BBD in optimizing the production of furfural from CSH, thus enhancing its potential as an economically viable feedstock for the biorefinery industry contributing to the advancement of biomass conversion technologies for the sustainable production of high-value chemicals.
Cotton (Gossypium hirsutum L.) is a major global crop, with India being the second-largest producer. The introduction of Bt cotton has revolutionized cultivation, but weeds remain a persistent challenge to productivity. This review discusses the impact of weeds on cotton yield and explores various agronomic interventions for effective weed management. Weeds significantly reduce cotton yield by competing for essential resources such as water, nutrients, sunlight, and space. They also act as hosts for pests and diseases further diminishing crop health and fiber quality. The critical window for managing weeds in cotton lasts for 11 to 12 weeks, starting one to two weeks post crop emergence, as neglecting weed control during this time can lead to significant yield losses, ranging from 10 to 90%. Various weed management strategies are discussed, including preventive measures (e.g., clean cultivation, weed-free seeds), cultural practices (e.g., crop rotation, intercropping), mechanical methods (e.g., hoeing, inter-row cultivation), and chemical interventions (e.g., herbicides). Each method has its advantages and limitations, necessitating an integrated approach for sustainable weed management. This review concludes that an integrated weed management approach, combining multiple strategies tailored to specific agro-ecological conditions, is crucial for effective weed control in cotton. Future research should focus on weed modeling to predict weed emergence patterns and develop precise weed control thresholds. Additionally, exploring methods to enhance crop competitiveness through cultivar selection, row spacing optimization, and irrigation/fertilization management can further improve weed management outcomes in cotton production.
Drought tolerance is a complicated trait that primarily involves genetic and physiological characteristics. Quantitative trait loci (QTL)-hotspot regions from an upland cotton (Gossypium hirsutum) cultivar (CNH 28I) were introgressed into a Pima cotton (G. barbadense) cultivar (Suvin) with superior fiber properties to increase drought tolerance in Pima cotton. To screen the recombinant inbred lines (RILs) derived from CNH 28IxSuvin, QTL-hotspot regions on different chromosomes were selected for drought-tolerant traits: osmotic pressure (OP), canopy temperature (CT), carbon isotope ratio (CIR), relative water content (RWC), root weight (RW), root length (RL), root tip (RT), root surface area (RSA), and root volume (RV). The cotton genome's 157 simple sequence repeat markers related to drought QTL-hotspots were used to genotype the RILs. RIL population amplified polymerase chain reaction products of the same size as the drought-tolerant parent CNH 28I revealed introgression of QTL-hotspot regions. Sixteen QTLs generated polymorphism in the RIL population and parents, of which five (NAU2557, CIR143b, MUSB0818c, JESPR0205, and BNL1053) were associated with CIR, five (NAU2474, BNL3594b, BNL2884, BNL3259, and BNL1153b) with OP, four (JESPR230c, BNL3347, MUSS096a, CI061b) with RV, one (BNL3173b) with RWC, and one (BNL1705) with RL. Using the physiological metrics of RWC, CT, chlorophyll, and fiber length, six improved lines with drought-tolerant characteristics and fiber length were chosen by genotyping and phenotyping.
RNAi-mediated silencing of target native gene(s) and CRISPR-mediated, targeted knockout of a gene represent two powerful tools to study gene function and to engineer useful traits in plants. Gossypol, present in most parts of the cotton plant, serves as a defense chemical against certain pests and pathogens. Gossypol and related terpenoids are synthesized and stored in lysigenous glands present in most aboveground parts of the plant. However, gossypol's presence also limits the suitability of the seeds for human and animal nutrition. Selective, seed-specific RNAi-mediated silencing of the members of a gene family encoding delta-cadinene synthase, which catalyzes a key step in gossypol biosynthesis, reduced gossypol levels by 97% exclusively in the seeds. One such ultra-low gossypol cottonseed (ULGCS) line, TAM66274, has been deregulated in the U.S. and its seeds are considered safe for consumption as food and as feed for animals. Although CRISPR/ Cas9-mediated knockout of the CGF3 gene, a key regulator of gland development, in a cotton plant eliminated the glands and their contents including gossypol in the seeds and other aboveground parts of the plant, it could not achieve the specificity of selective RNAi silencing. Thus, although it is possible to achieve seed-specific silencing of the target gene(s) using RNAi, it is not possible to eliminate their expression. In contrast, using the CRISPR system it is possible to knock out a target gene and its function entirely, tissue-specificity is difficult to obtain. Our investigations revealed both the positive attributes and limitations of RNAi and CRISPR/Cas9 technologies.
Mepiquat chloride (MC) application timing and plant spacing significantly influenced Bt cotton growth and yield parameters. MC application, irrespective of timing, reduced plant height, but the most pronounced effect was observed when sprayed at the squaring stage. This height reduction was associated with increased boll number per plant, particularly under high-density planting. Additionally, MC treatments resulted heavier bolls compared to the control, especially in wider spacings. Seed cotton yield (SCY) was significantly impacted by the interaction of MC timing and plant spacing. The highest SCY was achieved with MC applied at squaring, particularly at closer spacing, demonstrating a substantial yield advantage over the control. Both MC timings enhanced SCY at closer spacings, whereas the control yielded best at medium densities. These findings indicate that MC application the squaring stage is superior in reducing plant height, promoting boll development, and ultimately maximizing cotton yield, especially under high-density planting. Nevertheless, both MC timings can optimize cotton production, underscoring the critical role of tailored plant spacing for yield maximization. Future research should investigate the physiological mechanisms underpinning these responses and explore the potential of MC in conjunction with other agronomic practices to further enhance cotton productivity.
Developing stable, high-yielding Egyptian cotton (Gossypium barbadense) cultivars that can adapt to changing weather patterns and rising temperatures is one of the main goals of cotton breeders. Nineteen genotypes of G. barbadense were evaluated for stable yield over five consecutive Kharif seasons from 2019 to 2024. Genotype-by-environment interactions contributed 96.2% of the variance, highlighting their importance. Genotypes G3 and G4 consistently performed well under all conditions, with high mean yields, according to the Additive Main Effects and Multiplicative Interaction model. As there were more interactions, the relative performance of genotypic values, the harmonic mean of the relative performance of genotypic values, and the harmonic mean of genotypic values were used to estimate the principal components of Best Linear Unbiased Prediction (BLUP)-based simultaneous selection. Genotypes G10 and G9 exhibited the highest anticipated means for number of bolls. Additionally, based on their stability indices, genotypes G10, G9, G2, and G18, were stable in number of bolls produced. Genotypes G9, G18, and G10 presented more bolls and greater stability based on the weighted average absolute scores of BLUP. BLUP was more accurate in determining the stability of the genotypes. In this study, G2, G3, and G13 cotton genotypes were found to be stable across all the models.
