Explore the vast range of titles available.

Lint yield in cotton is governed by light intercepted by the canopy (IPAR), radiation use efficiency (RUE), and harvest index (HI). However, the conventional methods of measuring these yield-governing physiological parameters are labor-intensive, time-consuming and requires destructive sampling. This study aimed to explore the use of low-cost and high-resolution UAV-based RGB and multispectral imagery 1) to estimate fraction of IPAR (IPAR f ), RUE, and biomass throughout the season, 2) to estimate lint yield using the cotton fiber index (CFI), and 3) to determine the potential use of biomass and lint yield models for estimating cotton HI. An experiment was conducted during the 2021 and 2022 growing seasons in Tifton, Georgia, USA in randomized complete block design with five different nitrogen treatments. Different nitrogen treatments were applied to generate substantial variability in canopy development and yield. UAV imagery was collected bi-weekly along with light interception and biomass measurements throughout the season, and 20 different vegetation indices (VIs) were computed from the imagery. Generalized linear regression was performed to develop models using VIs and growing degree days (GDDs). The IPAR f models had R 2 values ranging from 0.66 to 0.90, and models based on RVI and RECI explained the highest variation (93%) in IPAR f during cross-validation. Similarly, cotton above-ground biomass was best estimated by models from MSAVI and OSAVI. Estimation of RUE using actual biomass measurement and RVI-based IPAR f model was able to explain 84% of variation in RUE. CFI from UAV-based RGB imagery had strong relationship (R 2 = 0.69) with machine harvested lint yield. The estimated HI from CFI-based lint yield and MSAVI-based biomass models was able to explain 40 to 49% of variation in measured HI for the 2022 growing season. The models developed to estimate the yield-contributing physiological parameters in cotton showed low to strong performance, with IPAR f and above-ground biomass having greater prediction accuracy. Future studies on accurate estimation of lint yield is suggested for precise cotton HI prediction. This study is the first attempt of its kind and the results can be used to expand and improve research on predicting functional yield drivers of cotton.

Light Detection and Ranging (LiDAR) technology can be used to assess canopy height in cotton (Gossypium hirsutum L.), but standardized data acquisition and processing guidelines are lacking. Accurate canopy height estimation is crucial in cotton for optimizing growth regulator application and maximizing yield. The main goal of this study was to determine the optimal unmanned aerial vehicle flight settings—altitude and speed—and assess specific processing parameters’ impact on data accuracy, processing time, and file size. Nine flight settings comprising three altitudes (12.2 m, 24.4 m, and 48.8 m) and three speeds (4.8 km/h, 9.6 km/h, and 14.4 km/h) were tested. LiDAR data were processed using DJI Terra software (v. 4.1.0), where two user-defined processing steps were examined: point-cloud thinning via grid size sub-sampling (0, 10, 20, 30, 40, and 50 cm) and slope classification (flat, gentle, and steep). The optimal flight altitude was 24.4 m, with no effect of flight speed. Grid sub-sampling up to 20 cm produced balanced accuracy, processing time, and file size. The choice of slope category had no significant effect on LiDAR-derived canopy height. These findings contribute to the development of standardized LiDAR data acquisition and processing guidelines for cotton to support crop management decision.

In this study, we investigated the potential involvement of endogenous viral elements (EVEs) in the development of apical tissue necrosis, resulting in the terminal abortion of upland cotton (Gossypium hirsutum L.) in Georgia. The high-throughput sequence analysis of symptomatic and asymptomatic plant tissue samples revealed near-complete EVE-Georgia (EVE-GA) sequences closely related to caulimoviruses. The analysis of EVE-GA’s putative open reading frames (ORFs) compared to cotton virus A and endogenous cotton pararetroviral elements (eCPRVE) revealed their similarity in putative ORFs 1–4. However, in the ORF 5 and ORF 6 encoding putative coat protein and reverse transcriptase, respectively, the sequences from EVE-GA have stop codons similar to eCPRVE sequences from Mississippi. In silico mining of the cotton genome database using EVE-GA as a query uncovered near-complete viral sequence insertions in the genomes of G. hirsutum species (~7 kb) but partial in G. tomentosum (~5.3 kb) and G. mustelinum (~5.1 kb) species. Furthermore, cotton EVEs’ episomal forms and messenger RNA (mRNA) transcripts were detected in both symptomatic and asymptomatic plants collected from cotton fields. No significant yield difference was observed between symptomatic and asymptomatic plants of the two varieties evaluated in the experimental plot. Additionally, EVEs were also detected in cotton seeds and seedlings. This study emphasizes the need for future research on EVE sequences, their coding capacity, and any potential role in host immunity or pathogenicity.

With grower interest in skip and wide row cotton systems, varietal performance in such systems has become a major question. An experiment was conducted in 2022 and 2023 in Tifton and Midville, GA, evaluating three row arrangements (standard 91‐cm row spacing, 2 × 1 skip row, and 183‐cm row spacing or wide row) and four commercially available varieties (Stoneville [ST] 5091 Bollgard 3 Xtendflex [B3XF], Phytogen [PHY] 400 Widestrike 3 Roundup Flex Enlist [W3FE], DynaGro [DG] 3799 B3XF, and Deltapine [DP] 1840 B3XF). There were no interactions between variety and row arrangement for any response variable, indicating the best variety for standard row spacings would also be the best variety in alternative row arrangements. Plant populations were reduced 32% and 53% in 2 × 1 skip‐row and wide‐row systems, respectively, compared to standard row arrangements, which accomplishes the major goal of these systems in reducing seed cost. Boll rot and hard lock were reduced in wide row treatments only, which could benefit cotton growers in the lower Southeast. However, reductions in lint yield were associated with 2 × 1 skip row (all site years) and wide row arrangements (three out of four site‐years) compared to the grower standard. Differences among varieties were observed in plant heights, lint yield, and fiber quality, which is to be expected. These results confirm much of the work conducted on skip and wide row cotton systems and indicate that for growers in the lower Southeast to achieve maximum lint yields, standard row arrangements are superior to alternative row arrangements. Core Ideas Cotton growers remain interested in skip‐ and wide‐row systems to reduce input costs. Plant population was reduced 32% and 53% in 2 × 1 skip and wide row treatments, respectively. Boll rot and hard lock was reduced in wide row arrangements, but not in 2 × 1 skip row treatments. In all four site‐years, lint yield was reduced in 2 × 1 skip row arrangements by 14%–32%. In three out of four site‐years, lint yield was reduced in wide row arrangements by 13%–31%.

Taxonomy: Cotton leafroll dwarf virus (CLRDV) is a member of the genus Polerovirus, family Solemoviridae. Geographical Distribution: CLRDV is present in most cotton‐producing regions worldwide, prominently in North and South America. Physical Properties: The virion is a nonenveloped icosahedron with T = 3 icosahedral lattice symmetry that has a diameter of 26–34 nm and comprises 180 molecules of the capsid protein. The CsCl buoyant density of the virion is 1.39–1.42 g/cm3 and S20w is 115–127S. Genome: CLRDV shares genomic features with other poleroviruses; its genome consists of monopartite, single‐stranded, positive‐sense RNA, is approximately 5.7–5.8 kb in length, and is composed of seven open reading frames (ORFs) with an intergenic region between ORF2 and ORF3a. Transmission: CLRDV is transmitted efficiently by the cotton aphid (Aphis gossypii Glover) in a circulative and nonpropagative manner. Host: CLRDV has a limited host range. Cotton is the primary host, and it has also been detected in different weeds in and around commercial cotton fields in Georgia, USA. Symptoms: Cotton plants infected early in the growth stage exhibit reddening or bronzing of foliage, maroon stems and petioles, and drooping. Plants infected in later growth stages exhibit intense green foliage with leaf rugosity, moderate to severe stunting, shortened internodes, and increased boll shedding/abortion, resulting in poor boll retention. These symptoms are variable and are probably influenced by the time of infection, plant growth stage, varieties, soil health, and geographical location. CLRDV is also often detected in symptomless plants. Control: Vector management with the application of chemical insecticides is ineffective. Some host plant varieties grown in South America are resistant, but all varieties grown in the United States are susceptible. Integrated disease management strategies, including weed management and removal of volunteer stalks, could reduce the abundance of virus inoculum in the field. This review provides insight into cotton leafroll dwarf disease, which is caused by cotton leafroll dwarf virus, including its host range, evolution, diagnosis, tissue tropism, yield loss, and management.

Integrated weed management practices that reduce selection for resistance on herbicides are critical to delay resistance. To quantify the reduction in selection for resistance placed on Palmer amaranth from 2,4-D applied postemergence in cotton, an experiment was conducted three times in Georgia during 2020 and 2021 evaluating the benefits of (i) a cover crop, (ii) preemergence herbicides, and (iii) timeliness of applications. When a timely total-postemergence program of glyphosate + 2,4-D was applied three times over the season in a conventionally tilled system, 281,690 glyphosate-resistant Palmer amaranth plants ha–1 were exposed to 2,4-D. Over 61,500 of these plants were exposed to multiple 2,4-D applications. Altering the production system to conservation tillage, and including a rolled-rye cover crop, reduced the total number of plants exposed to 2,4-D for the season by 72% and the number of plants exposed multiple times by 60%. Even more effective, including a mixture of residual preemergence herbicides reduced the number of plants exposed to 2,4-D at least once over 99.9%, and reduced multiple exposures over 99.3% for the season; this benefit was observed for both conventional and conservation tillage systems. Delaying the initial application of the total-postemergence program did not influence the number of Palmer amaranth plants treated at least once but increased the number of plants treated multiple times by a factor of 3.7 times. As a result of early-season weed competition, cotton height and yield reductions were also associated with both lack of preemergence residuals and delayed postemergence applications. When considering the goal of minimizing the number of Palmer amaranth treated with a postemergence application of 2,4-D in a cotton system, the preemergence was the most effective option followed by (fb) the cover crop fb making timely postemergence applications. However, the most effective approach was to utilize each of these tactics in the same growing season. Nomenclature: 2,4-D; glyphosate; Palmer amaranth; Amaranthus palmeri S. Watson; cotton; Gossypium hirsutum

Herbicides that inhibit protoporphyrinogen oxidase (PPO) are used in more than 40 agronomic and specialty crops across Georgia to manage weeds through residual and postemergence (POST) control. In 2017, a population of Palmer amaranth exhibiting reduced sensitivity to POST applications of PPO-inhibiting herbicides was identified by the University of Georgia. Seed were collected from the site along with a known sensitive population; distance between the samples was 200 m, increasing the likelihood of similar environmental and genetic characteristics. To quantify sensitivity for both preemergence (PRE) and POST uses, 21 greenhouse dose-response assessments were conducted from 2017 to 2022. After conducting initial rate-response studies, 13 doses per herbicide were chosen for the POST experiment; field use rates of fomesafen (420 g ai ha–1), lactofen (219 g ai ha–1), acifluorfen (420 g ai ha–1), and trifludimoxazin (25 g ai ha–1) ranging from 0× to 4× the field use rate for the susceptible population, and 0× to 40× for the suspect population were applied. Herbicide treatments included adjuvants and were applied to plants 8 to 10 cm in height. Relative resistance factors (RRFs) were calculated for control ratings, mortality, and biomass, and ranged from 105 to 318, 36 to 1,477, 215 to 316, and 9 to 49 for fomesafen, lactofen, acifluorfen, and trifludimoxazin, respectively. In the PRE experiment, herbicide applications included five to nine doses of fomesafen (1× = 210 g ai ha–1), flumioxazin (1× = 57 g ai ha–1), oxyfluorfen (1× = 561 g ai ha–1), and trifludimoxazin (1× = 38 g ai ha–1); doses ranged from 0× to 6× for the suspect population and 0× to 2× for the susceptible population. Visual control, mortality, and biomass RRFs ranged from 3 to 5 for fomesafen, 21 to 31 for flumioxazin, 6 to 22 for oxyfluorfen, and 8 to 38 for trifludimoxazin. Results confirm that a Georgia Palmer amaranth population is resistant to PPO-inhibiting herbicides applied both PRE and POST. Nomenclature: Aciflurofen; flumioxazin; fomesafen; lactofen; oxyfluorfen; trifludimoxazin; Palmer amaranth; Amaranthus palmeri S. Watson; cotton; Gossypium hirsutum L.; peanut, Arachis hypogaea L.; soybean, Glycine max (L.)

Optimizing irrigation termination time can save water and preserve lint yield and fiber quality in cotton. Although there is currently an irrigation termination recommendation in Georgia, the ideal time for termination could be influenced by cultivar differences in maturity. The hypotheses of this study were that differential irrigation termination times will affect lint yield, fiber quality, and incidence of hardlock and boll rot, and responses will be dependent on cultivar differences in maturity. In 2021 and 2022, a study was conducted in Camilla, GA, using two cotton cultivars with contrasting maturities under four irrigation termination treatments. Irrigation was terminated at cutout, first open boll, 2 weeks after first open boll, and 4 weeks after first open boll. Measurements included plant growth, cutout date, lint yield, irrigation water use efficiency (IWUE), fiber quality, and incidence of boll diseases. Gas exchange measurements and percent open boll estimates at each irrigation termination time were also conducted. Terminating irrigation at cutout did not significantly affect yield in either year; however, IWUE increased 12.6% relative to current recommendations and 13.2% relative to the latest termination time in the 2022 season. Cultivars differed significantly in cutout date, agronomic maturity, gas exchange rates, yield, hardlock/boll rot incidence, and fiber quality. However, there was no interaction between cultivar and irrigation termination time for any parameter. We conclude that irrigation can be terminated at cutout to maximize IWUE, for early and late‐maturing cultivars, without limiting yield or fiber quality, assuming a water‐replete soil profile at termination. Core Ideas Defining early irrigation termination times that do not penalize yield in cotton can increase water use efficiency. Terminating irrigation at cutout maximized water use efficiency in an early and a late maturing cultivar. Cultivar affected yield, fiber quality, water use efficiency, and disease incidence.

The most widely planted cotton (Gossypium hirsutum L.) and soybean [Glycine max (L.) Merr.] varieties in the United States are resistant to the herbicide dicamba. Measures to reduce selection pressure for dicamba‐resistant weeds is paramount. Four studies evaluated strategies to reduce selection pressure for Palmer amaranth (Amaranthus palmeri S. Watson) resistance to dicamba applied postemergence (POST) in cotton. A split‐plot arrangement consisted of conventional tillage or cereal rye (Secale cereale L.) cover crop as the whole plot. The subplot included four herbicide systems: no herbicide, 3 POSTs, fomesafen plus diuron applied pre‐emergence (PRE) followed by (fb) 3 POSTs, and PRE fb 2 POSTs fb diuron plus monosodium methyl arsenate applied lay‐by post‐directed (LPD). The POST herbicide applications were glyphosate plus dicamba. The cover crop reduced Palmer amaranth density 75, 70, and 54% at the time of POST 1, POST 2, and POST 3 application, respectively. Pre‐emergence herbicides fb POST applications reduced Palmer amaranth densities 99, 99, and 96% at the aforementioned application timings, respectively. Cover crop plus PRE herbicides provided similar reductions. Cumulative for the season, Palmer amaranth exposure to dicamba was reduced 65% by the cover crop, 98% by both PRE herbicides and cover crop plus PRE herbicides compared to 3 POST applications. An LPD application reduced Palmer amaranth exposure to dicamba by 38,319 plants ha–1 compared to a third POST. Cotton stand was higher in conventional systems when soil temperatures were 30–37 °C during emergence; however, stand in the cover crop was greater when soil temperatures were 40–43 °C. Yields were reduced 14% in a total POST herbicide program, and were improved 14% in a cover crop. A cereal rye cover crop and residual PRE herbicides had the biggest impact on reducing selection pressure for Palmer amaranth resistance to dicamba while also improving yield. Core Ideas Herbicide‐resistant Palmer amaranth is a major pest in cropping systems across the United States. Integrated weed management tactics are needed to delay further weed resistance issues. Cover crops plus pre‐emergence herbicides reduced Palmer amaranth exposure to dicamba 98%. Replacing a third postemergence with a lay‐by reduced exposure to dicamba 38,319 plants ha‐1. Cotton yield was highest when utilizing a cover crop and pre‐emergence herbicides.

The tolerance of cereal rye to eight herbicides registered for use in wheat, at two rates, was evaluated for potential labeling in cereal rye to expand limited chemical weed control options. Across five site-years, halauxifen-methyl + florasulam, pyroxsulam, and thifensulfuron-methyl + tribenuron-methyl applied at a 2X rate to cereal rye at Zadoks (Z) 13 caused less than 15% injury and had no impact on cereal rye density. These herbicides at the 2X rate reduced cereal rye heights 11% at 10 days after treatment (DAT), with rye recovering by 31 DAT; cereal rye heights were not reduced with these herbicides at their 1X rate. In contrast, significant injury was observed with the 1X rate of mesosulfuron-methyl (45%), pinoxaden (27%), and pinoxaden + fenoxaprop-P-ethyl (30%) applied postemergence; early-season height was reduced 19% to 26%. Residual herbicide pyroxasulfone applied as a delayed preemergence at Z 10 and flumioxazin + pyroxasulfone applied at Z 11 caused 27% to 28% and 16% to 47% injury, respectively, when the 1X rate was activated by rainfall within 2 d of application. These residual herbicides reduced cereal rye height and density up to 35% and 40%, respectively. Cereal rye grain yield was not influenced by herbicide or rate applied. Nomenclature: fenoxaprop-P-ethyl; flumioxazin; halauxifen-methyl; pyroxasulfone; florasulam; mesosulfuron-methyl; pinoxaden; pyroxsulam; thifensulfuron-methyl; tribenuron-methyl; cereal rye, Secale cereale L.; wheat, Triticum aestivum L.