Daniel B. Reynolds

Effect of Adjuvants and Urea Ammonium Nitrate on Bispyribac Efficacy, Absorption, and Translocation in Barnyardgrass (Echinochloa crus-galli). I. Efficacy, Rainfastness, and Soil Moisture

Abstract Bispyribac is registered for postemergence control of broadleaf, sedge, and grass weeds in rice. Bispyribac inhibits the acetolactate synthase enzyme in sensitive plants. Herbicides in this class of chemistry require a spray adjuvant to achieve optimal efficacy, often achieve different levels of weed control according to the spray adjuvant used, and typically have rainfast periods of at least 6 to 8 h. Efficacy and rainfastness of bispyribac can be affected by spray adjuvant and the addition of urea ammonium nitrate (UAN). Greenhouse experiments were conducted to investigate the effect of spray adjuvant type, addition of UAN, and soil moisture on bispyribac efficacy on barnyardgrass. Control of barnyardgrass was improved when UAN was added to bispyribac at 0.4 or 0.8 g ha−1 plus an organosilicone-based nonionic surfactant (OSL/NIS) or methylated seed oil/organosilicone (MSO/OSL) spray adjuvant. The type of adjuvant added to the spray solution affected bispyribac efficacy on barnyardgrass. The addition of UAN decreased the rainfast period from 8 h (registered rainfast period) to 1 or 4 h (99 to 100% control) when either the OSL/NIS or MSO/OSL adjuvant was applied with bispyribac, respectively. Applying UAN and OSL/NIS or MSO/OSL adjuvant with bispyribac enhanced efficacy and reduced the time period required between bispyribac application and washoff during a rainfall event. Increasing soil moisture conditions resulted in greater efficacy from bispyribac when applied with and without UAN. Nomenclature: Bispyribac; barnyardgrass, Echinochloa crus-galli (L.) Beauv. ECHCG; rice, Oryza sativa L.

Effect of Adjuvant and Urea Ammonium Nitrate on Bispyribac Efficacy, Absorption, and Translocation in Barnyardgrass (Echinochloa crus-galli). II. Absorption and Translocation

Abstract Inconsistent control of barnyardgrass with bispyribac may be alleviated through adjuvant technology. Experiments were conducted to determine the effect of adjuvant and urea ammonium nitrate (UAN) on absorption and translocation of bispyribac in barnyardgrass. Additional experiments were conducted to determine when maximum absorption and translocation occurred with the use of a methylated seed oil/organosilicone adjuvant (MSO/OSL) plus UAN (0.37 L ha−1 and 2% v/v). In the initial experiment, 14C-bispyribac–treated leaves, nontreated leaves, and roots were collected 6 and 24 h after application. Absorption was greatest with tank-mixed MSO/OSL (0.37 L ha−1) plus UAN (2% v/v) and the proprietary blend of MSO/OSL/UAN (2% v/v) at 80 and 74% of applied 14C-bispyribac, respectively. Translocation to nontreated leaves and roots was also highest with these treatments. Increased translocation appeared to be due to greater herbicide absorption, not an increase in translocation rate. The addition of 32% UAN to MSO/OSL and nonionic organosilicone (OSL/NIS) adjuvant systems resulted in a four to fivefold increase in absorption compared with treatments without UAN. Recovery of 14C-bispyribac in additional experiments generally decreased as time after application increased; however, recovery was 86% or greater for all time intervals. By 12 h after application, 68% of applied 14C-bispyribac was absorbed. At this time, 14C-bispyribac was partitioned within the plant in the following manner: 48% in the treated area, 10% in leaf tissue from treated area to tip of the treated leaf, 1.9% in leaf tissue from treated area to collar region of the treated leaf, 1.6% in remaining leaves from collar of treated leaf upward, 5.3% in remaining leaves from collar of treated leaf downward to soil line, and 0.7% in the roots. These data indicate that maximum absorption was achieved within 12 h with a tank mix of MSO/OSL and UAN or the MSO/OSL/UAN blend. Nomenclature: Bispyribac; barnyardgrass, Echinochloa crus-galli (L.) Beauv. ECHCG

Sensitivity of hyperspectral classification algorithms to training sample size

Algorithms that exploit hyperspectral imagery often encounter problems related to the high dimensionality of the data, particularly when the amount of training data is limited. Recently, two algorithms were proposed to alleviate the small sample size problem - one is based on employing a Multi-Classifier Decision Fusion (MCDF) in the raw reflectance domain, and the other employed the MCDF framework in the Discrete Wavelet Transform domain (DWT-MCDF). This paper investigates the sensitivity of conventional single classifier based classification approaches, as well as MCDF and DWT-MCDF to variations in the amount of data employed for training the classification system. The hyperspectral data in this experiment was obtained using an airborne hyperspectral imager used by SpecTIR™. The results of the experimental analysis show that for the given application, the MCDF and DWT-MCDF algorithms are significantly less sensitive than the conventional algorithms to limited training data. PCA consistently results in overall accuracies of about 35%. LDA accuracies are very high, about 75%, when there is an abundance of training data - about 10X (i.e. number of training samples is 10 times the number of spectral bands); remains above 60% for training data abundances of 2X and higher; but dramatically decreases to ∼20% for abundances of 1X. MCDF results in accuracies ranging between 65% and 75% for training data abundance of 3X and higher, but the accuracies drop to ∼60% for 2X and ∼55% for 1X. DWT-MCDF results in high accuracies with the least sensitivity to training data abundance. Its accuracies range between ∼60–65% for abundances of 1X to 10X.

Effect of Pendimethalin Formulation and Application Rate on Cotton Fruit Partitioning

Abstract Because of the development of glyphosate-resistant weed species, the lack of new herbicide chemistry, and the late-season emergence of annual grass species, efforts are underway to expand the use of currently available herbicides for use in cotton. Field studies were conducted in 2005 and 2006 to evaluate the effect of POST-applied pendimethalin formulation and application rate on cotton fruit partitioning. Oil- and water-based pendimethalin formulations as well as S-metolachlor were applied to cotton that had four true leaves. All pendimethalin and S-metolachlor applications included glyphosate for broad-spectrum weed control. Pendimethalin formulation and application rate had no effect on seed-cotton partitioning to horizontal fruiting zones, on second- or third-position horizontal fruiting sites, or on monopodial branches. However, increased seed-cotton partitioned to plants that had lost apical dominance was observed when the water-based pendimethalin formulation was applied at rates of 1.7 kg ai/ha and higher as well as when the oil-based pendimethalin formulation was applied at 3.3 kg ai/ha. Application of water-based pendimethalin at rates of 1.7 and 3.4 kg ai/ha and oil-based pendimethalin at rates of 0.8, 1.7, and 3.3 kg ai/ha resulted in reduced seed-cotton located at position 1 fruiting sites compared with the untreated check. POST application of S-metolachlor had no effect on fruit partitioning to horizontal fruiting positions or vertical fruiting zones. Minor differences in seed-cotton partitioning to cohorts and individual fruiting nodes were observed from application of glyphosate, pendimethalin, and S-metolachlor. However, no differences in seed-cotton yield were observed from application of glyphosate, S-metolachlor, or pendimethalin, regardless of formulation or application rate. POST pendimethalin application at rates less than 1.7 kg ai/ha is relatively safe and should provide cotton producers with an additional tool for herbicide-resistant weeds and late-season annual grasses.

Glyphosate Tolerance in Enhanced Glyphosate-Resistant Cotton (Gossypium hirsutum)

Abstract Glyphosate applied to glyphosate-resistant (RR) cotton varieties after the four-leaf stage can decrease boll retention resulting in severe yield reductions. Enhanced glyphosate-resistant cotton (RR Flex), released for commercial use in 2006, offers a wider window of glyphosate applications without the risk of yield loss. However, no data exist regarding the effect of glyphosate application, especially late season applications, on fruit partitioning in RR Flex cotton. The objective of this research was to determine the effect of glyphosate rate and application timing on RR Flex cotton yield and fruit partitioning compared with current RR cotton. Studies were conducted during a 3-yr period (2004 to 2006), throughout the cotton growing regions of Mississippi. Roundup Ready (ST 4892 Bollgard/Roundup Ready [BR]) and Roundup Ready Flex (Mon 171 Enhanced Roundup Ready and ST 4554 Bollgard II/Roundup Ready Flex [B2RF]) cotton was planted, and glyphosate was applied at various rates and cotton growth stages. Data were collected using box mapping, a technique designed to depict yield partitioning on a cotton plant. RR Flex cotton yields were unaffected by glyphosate application timing or rate. Yields for ST 4892 BR were affected by application timings after the sixth leaf. ST 4892 BR had increased yield partitioning to position-three bolls and upper nodes with later application timings of glyphosate. Increases in seed cotton partitioned to higher nodes and outer fruiting positions were unable to compensate for fruit shed from innermost, lower fruiting sites. These data indicate that RR Flex cotton has excellent tolerance to late-season glyphosate applications. Nomenclature: Glyphosate; cotton, Gossypium hirsutum L.

Seedbank Persistence of Palmer Amaranth (Amaranthus palmeri) and Waterhemp (Amaranthus tuberculatus) across Diverse Geographical Regions in the United States

Abstract Knowledge of the effects of burial depth and burial duration on seed viability and, consequently, seedbank persistence of Palmer amaranth (Amaranthus palmeri S. Watson) and waterhemp [Amaranthus tuberculatus (Moq.) J. D. Sauer] ecotypes can be used for the development of efficient weed management programs. This is of particular interest, given the great fecundity of both species and, consequently, their high seedbank replenishment potential. Seeds of both species collected from five different locations across the United States were investigated in seven states (sites) with different soil and climatic conditions. Seeds were placed at two depths (0 and 15cm) for 3 yr. Each year, seeds were retrieved, and seed damage (shrunken, malformed, or broken) plus losses (deteriorated and futile germination) and viability were evaluated. Greater seed damage plus loss averaged across seed origin, burial depth, and year was recorded for lots tested at Illinois (51.3% and 51.8%) followed by Tennessee (40.5% and 45.1%) and Missouri (39.2% and 42%) for A. palmeri and A. tuberculatus, respectively. The site differences for seed persistence were probably due to higher volumetric water content at these sites. Rates of seed demise were directly proportional to burial depth (α=0.001), whereas the percentage of viable seeds recovered after 36 mo on the soil surface ranged from 4.1% to 4.3% compared with 5% to 5.3% at the 15-cm depth for A. palmeri and A. tuberculatus, respectively. Seed viability loss was greater in the seeds placed on the soil surface compared with the buried seeds. The greatest influences on seed viability were burial conditions and time and site-specific soil conditions, more so than geographical location. Thus, management of these weed species should focus on reducing seed shattering, enhancing seed removal from the soil surface, or adjusting tillage systems.

Spray droplet size and carrier volume effect on dicamba and glufosinate efficacy: Drop size and carrier volume efficacy effect

BACKGROUND Pesticide applications using a specific droplet size and carrier volume could maximize herbicide efficacy while mitigating particle drift in a precise and efficient manner. The objectives of this study were to investigate the influence of spray droplet size and carrier volume on dicamba and glufosinate efficacy, and to determine the plausibility of droplet-size based site-specific weed management strategies. RESULTS Generally, across herbicides and carrier volumes, as droplet size increased, weed control decreased. Increased carrier volume (187 L ha-1 ) buffered this droplet size effect, thus greater droplet sizes could be used to mitigate drift potential while maintaining sufficient levels of weed control. To mitigate drift potential and achieve satisfactory weed control (≥ 90% of maximum observed control), a 900 µm (Ultra Coarse) droplet size paired with 187 L ha-1 carrier volume is recommended for dicamba applications and a 605 µm (Extremely Coarse) droplet size across carrier volumes is recommended for glufosinate applications. Although general droplet size recommendations were created, optimum droplet sizes for weed control varied significantly across site-years. CONCLUSION Convoluted interactions occur between droplet size, carrier volume, and other application parameters. Recommendations for optimizing herbicide applications based on droplet size should be based on a site-specific management approach to better account for these interactions.

Evaluation of Dicamba Persistence among Various Agricultural Hose Types and Cleanout Procedures Using Soybean (Glycine max) as a Bio-Indicator

Synthetic rubbers, synthetic plastic polymers (polyvinyl chlorides [PVC]), polyurethane blends, and polyethylene blends make up modern-day agricultural spray hoses. The objective of this study was to determine whether agricultural hose types would differ with respect to 3,6-dichloro-2-methoxybenzoic acid (dicamba) sequestration. Field and greenhouse studies were conducted to evaluate the sequestration potential of dicamba within five agricultural hose types when cleaned with different cleanout procedures. Rinsate solutions were applied to soybean, which was used as a bio-indicator to test for cleanout efficiency. Differences among hose types and cleanout procedures exist with observations including soybean injury, height reduction, dry matter, yield, and part per million by volume (ppmv) analyte retained. The makeup of PVC polyurethane-blend and synthetic rubber–blend hoses increased retention of dicamba analyte when compared with the polyethylene blend hose. No differences were observed after the addition of ammonia to the cleanout solution when compared with water alone. Differences in a hose types ability to sequester the dicamba analyte may have more to do with the hoses internal chemical composition, manufacturing process, and composition breakdown. Scanning electron microscopy revealed imperfections in new PVC polyurethane and synthetic rubber hoses that eventually lead to inner wall depletion of these hose types. This is in contrast to what was found in the polyethylene-blend hose type, in which the inner wall is smooth and free of imperfections. Nomenclature: dicamba; soybean, Glycine max (L.) Merr.

Game theory based data fusion for precision agriculture applications

This paper investigates the utilization of game theory models for automated analysis of hyperspectral imagery fused with other remotely sensed and/or in situ data. The author analyzes two approaches to using strategic, competitive game theory models for groundcover classification, including the application of game theory models to (i) feature-level fusion and (ii) decision fusion for hypertemporal-hyperspectral datasets. Proposed model (i) uses conflict data filtering based on mutual entropy along with the Nash equilibrium as the means to find a steady state solution. Proposed model (ii) utilizes a strategic coalition game, specifically the weighted majority game (WMG). Both models are implemented under the assumption that all players are rational. The author incorporates each of the proposed approaches, (i) and (ii), into a multi-classifier decision fusion (MCDF) system for automated ground cover classification of hyperspectral imagery collected via an unmanned airborne system (UAS) over multiple dates. The paper provides experimental results demonstrating the efficacy of the proposed game theoretic approaches, presenting significant improvements over existing methods.

Utilization of local and global hyperspectral features via wavelet packets and multiclassifiers for robust target recognition

In this study, the authors investigate the combination of the wavelet packet decomposition (WPD) and multiclassifiers and decision fusion (MCDF) for a robust hyperspectral classification system. The authors investigate the use of the WPD multiresolution feature grouping and selection, forming groups of local and global spectral features, where each group is input to a classifier, resulting in local and global classifications. Then the labels are fused to form one class label. The classification system was applied to hyperspectral data for an agricultural application, namely the detection of different soybean rust infestation levels. The system was compared to current state-of-the-art hyperspectral analysis techniques to determine its comparative efficacy as compared to more conventional approaches, such as stepwise-linear discriminant analysis (LDA) or discriminant analysis feature extraction (DAFE) and current state-of-the art approaches, like spectral-domain multiclassifiers and decision fusion (MCDF). The proposed system had a classification accuracy which was approximately 40% higher than the SLDA approach and approximately 15% higher than MCDF.