The impact of thiamethoxam on the feeding and behavior of 2 soybean herbivore feeding guilds

Over the past few decades, inadvertent consequences have stemmed from the intensified use of neonicotinoids in agroecosystems. Neonicotinoid applications can result in both positive (e.g., reduced persistent virus transmission) and negative (e.g., increased host susceptibility) repercussions exhibiting ambiguity for their use in crop production. In soybean, aspects of neonicotinoid usage such as the impact on nonpersistent virus transmission and efficacy against nontarget herbivores have not been addressed. This study evaluated the interaction between the neonicotinoid thiamethoxam and soybean variety and the impact on different pest feeding guilds. Feeding and behavioral bioassays were conducted in the laboratory to assess the effect of thiamethoxam on the mortality and weight gain of the defoliator, Chrysodeixis includens (Walker). Bioassays evaluated impacts dependent and independent of soybean tissue, in addition to both localized and systemic efficacy within the soybean plant. Additionally, using the electrical penetration graph technique (EPG), the probing behavior of 2 piercing-sucking pests, Aphis gossypii Glover and Myzus persicae (Sulzer), was observed. Results from defoliator bioassays revealed thiamethoxam had insecticidal activity against C. includens. Distinctions in thiamethoxam-related mortality between bioassays dependent and independent of soybean tissue (~98% versus ~30% mortality) indicate a contribution of the plant towards defoliator-related toxicity. Observations of defoliator feeding behavior showed a preference for untreated soybean tissue relative to thiamethoxam-treated tissue, suggesting a deterrent effect of thiamethoxam. EPG monitoring of probing behavior exhibited a minimal effect of thiamethoxam on piercing-sucking herbivores. Findings from this study suggest neonicotinoids like thiamethoxam may provide some benefit via insecticidal activity against nontarget defoliators.

Elucidating the insecticidal mechanisms of zein nanoparticles on Anticarsia gemmatalis (Lepidoptera: Erebidae)

Previous research suggested that positively charged zein nanoparticles [(+)ZNP] were toxic to neonates of Anticarsia gemmatalis Hübner and deleterious to noctuid pests. However, specific modes of action for ZNP have not been elucidated. Diet overlay bioassays attempted to rule out the hypothesis that A. gemmatalis mortality was caused by surface charges from component surfactants. Overlay bioassays indicated that negatively charged zein nanoparticles [(-)ZNP] and its anionic surfactant, sodium dodecyl sulfate (SDS), exhibited no toxic effects when compared to the untreated check. Nonionic zein nanoparticles [(N)ZNP] appeared to increase mortality compared to the untreated check, though larval weights were unaffected. Overlay results for (+)ZNP and its cationic surfactant, didodecyldimethylammonium bromide (DDAB), were found to be consistent with former research indicating high mortalities, and thus, dosage response curves were conducted. Concentration response tests found the LC50 for DDAB on A. gemmatalis neonates was 208.82 a.i./ml. To rule out possible antifeedant capabilities, dual choice assays were conducted. Results indicated that neither DDAB nor (+)ZNP were antifeedants, while SDS reduced feeding when compared to other treatment solutions. Oxidative stress was tested as a possible mode of action, with antioxidant levels used as a proxy for reactive oxygen species (ROS) in A. gemmatalis neonates, which were fed diet treated with different concentrations of (+)ZNP and DDAB. Results indicated that both (+)ZNP and DDAB decreased antioxidant levels compared to the untreated check, suggesting that both (+)ZNP and DDAB may inhibit antioxidant levels. This paper adds to the literature on potential modes of action by biopolymeric nanoparticles.

Effects of Floquet Engineering on the Coherent Exciton Dynamics in Monolayer WS2

Coherent optical manipulation of electronic bandstructures via Floquet Engineering is a promising means to control quantum systems on an ultrafast time scale. However, the ultrafast switching on/off of the driving field comes with questions regarding the limits of the Floquet formalism (which is defined for an infinite periodic drive) through the switching process and to what extent the transient changes can be driven adiabatically. Experimentally addressing these questions has been difficult, in large part due to the absence of an established technique to measure coherent dynamics through the duration of the pulse. Here, using multidimensional coherent spectroscopy we explicitly excite, control, and probe a coherent superposition of excitons in the K and K' valleys in monolayer WS₂. With a circularly polarized, red-detuned pump pulse, the degeneracy of the K and K' excitons can be lifted, and the phase of the coherence rotated. We directly measure phase rotations greater than π during the 100 fs driving pulse and show that this can be described by a combination of the AC-Stark shift of excitons in one valley and the Bloch-Siegert shift of excitons in the opposite valley. Despite showing a smooth evolution of the phase that directly follows the intensity envelope of the nonresonant pump pulse, the process is not perfectly adiabatic. By measuring the magnitude of the macroscopic coherence as it evolves before, during, and after the nonresonant pump pulse we show that there is additional decoherence caused by power broadening in the presence of the nonresonant pump. This nonadiabaticity arises as a result of interactions with the otherwise adiabatic Floquet states and may be a problem for many applications, such as manipulating qubits in quantum information processing; however, these measurements also suggest ways such effects can be minimized or eliminated.

Evidence for Two Soybean Looper Strains in the United States with Limited Capacity for Cross-Hybridization

The noctuid moth soybean looper (SBL), Chrysodeixis includens (Walker) is an economically important pest of soybeans (Glycine max (L.) Merr.) in the southeastern United States. It has characteristics that are of particular concern for pest mitigation that include a broad host range, the capacity for annual long-distance flight, and resistance in some populations to important pesticides such as pyrethroids and chitin synthesis inhibitor. The biology of SBL in the United States resembles that of the fellow noctuid fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith), a major pest of corn and several other crops. FAW exhibits a population structure in that it can be divided into two groups (host strains) that differ in their host preferences but are broadly sympatric and exhibit incomplete reproductive isolation. In this paper, strategies used to characterize the FAW strains were applied to SBL to assess the likelihood of population structure in the United States. Evidence is presented for two SBL strains that were defined phylogenetically and display differences in the proportions of a small set of genetic markers. The populations exhibit evidence of reproductive barriers sufficient to allow persistent asymmetry in the distribution of mitochondrial haplotypes. The identified molecular markers will facilitate studies characterizing the behaviors of these two populations, with relevance to pest mitigation and efforts to prevent further dispersal of the resistance traits.

Investigating the Migratory Behavior of Soybean Looper, a Major Pest of Soybean, through Comparisons with the Corn Pest Fall Armyworm Using Mitochondrial Haplotypes and a Sex-Linked Marker

The Noctuid moth soybean looper (SBL), Chrysodeixis includens (Walker), is an economically important pest of soybean (Glycine max (Linnaeus) Merrill). Because it is not known to survive freezing winters, permanent populations in the United States are believed to be limited to the southern regions of Texas and Florida, yet its geographical range of infestations annually extend to Canada. This indicates annual migrations of thousands of kilometers during the spring and summer growing season. This behavior is like that of the fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith), also a Noctuid that is a major global pest of corn. SBL and FAW are projected to have very similar distributions of permanent populations in North America based on climate suitability modeling and the overlap in the distribution of their preferred host plants (corn and soybean). It therefore seems likely that the two species will display similar migratory behavior in the United States. This was tested by identifying genetic markers in SBL analogous to those successfully used to delineate FAW migratory pathways and comparing the distribution patterns of the markers from the two species. Contrary to expectations, the results indicate substantial differences in migratory behavior that appear to be related to differences in the timing of corn and soybean plantings. These findings underscore the importance of agricultural practices in influencing pest migration patterns, in particular the timing of host availability relative to mean seasonal air transport patterns.

Field applications of zein as a precise nanoscale delivery system for methoxyfenozide

When insecticides are applied in the environment, much of the product does not reach the target pest. Biopolymeric nanoparticles as nanocarriers have the potential to improve insecticide efficacy by improving absorption, coverage, and permeability while protecting the insecticide active ingredient from abiotic conditions and extending efficacy through controlled release. We conducted a series of experiments using a biopolymeric nanoparticle synthesized from zein, a biodegradable maize protein, to compare efficacy of a nanodelivered hydrophobic insect growth regulator (methoxyfenozide) against a commercial formulation. Positively charged zein nanoparticles (empty and loaded with methoxyfenozide) were compared to the formulated product, Intrepid 2F, as a foliar spray in-field on soybean. Chrysodeixis includens (Walker) was used as a model and was fed sprayed soybean leaves to evaluate efficacy of the tested foliar products over time. A separate set of leaves was sampled to measure residue levels of methoxyfenozide (MFZ) over time following foliar application using QuEChERS extraction and high-resolution liquid chromatography-mass spectrometry. Regression analysis found no differences in mortality slopes between positively charged zein nanoparticles loaded with methoxyfenozide [(+)ZNP(MFZ)] and Intrepid 2F, suggesting comparable efficacy of the synthesized nanoparticles to a commercial product. Higher concentrations of MFZ were present in (+)ZNP(MFZ)-treated in leaf tissue at 3 d following spray when compared to Intrepid 2F. The multiyear study results demonstrate that nanoparticles loaded with MFZ are comparable to Intrepid 2F under field conditions, with potential short-term benefits.

Catalyzing systemic movement of inward rectifier potassium channel inhibitors for antifeedant activity against the cotton aphid, Aphis gossypii (Glover)

BACKGROUND

The cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae), is a destructive agricultural pest, capable of photosynthate removal and plant virus transmission. Therefore, we aimed to test the antifeedant properties of small-molecule inhibitors of inward rectifier potassium (Kir) channels expressed in insect salivary glands and develop an approach for enabling systemic movement of lipophilic Kir inhibitors.

RESULTS

Two Kir channel inhibitors, VU041 and VU730, reduced the secretory activity of the aphid salivary glands by 3.3-fold and foliar applications of VU041 and VU730 significantly (P < 0.05) increased the time to first probe, total probe duration, and nearly eliminated phloem salivation and ingestion. Next, we aimed to facilitate systemic movement of VU041 and VU730 through evaluation of a novel natural product based solubilizer containing rubusoside that was isolated from Chinese sweet leaf (Rubus suavissimus) plants. A single lower leaf was treated with Kir inhibitor soluble liquid (KI-SL) and systemic movement throughout the plant was verified via toxicity bioassays and changes to feeding behavior through the electrical penetration graph (EPG) technique. EPG data indicate KI-SL significantly reduced ability to reach E1 (phloem salivation) and E2 (phloem ingestion) waveforms and altered plant probing behavior when compared to the untreated control. High-performance liquid chromatography (HPLC) analysis indicated the presence of VU041 and VU730 in the upper leaf tissue of these plants. Together, these data provide strong support that incorporation of rubusoside with Kir inhibitors enhanced translaminar and translocation movement through the plant tissue.

CONCLUSION

These data further support hemipteran Kir channels as a target to prevent feeding and induce toxicity. Further, these studies highlight a novel delivery approach for generating plant systemic activity of lipophilic insecticides. © 2022 Society of Chemical Industry.

Evaluation of Hemp (Cannabis sativa) (Rosales: Cannabaceae) as an Alternative Host Plant for Polyphagous Noctuid Pests

Hemp (Cannabis sativa L.) is a reemerging crop in the United States with increasing outdoor acreage in many states. This crop offers a potential host for polyphagous, defoliating lepidopteran pests currently present in Louisiana. The ability of soybean looper [Chrysodeixis includens (Walker)] (Lepidoptera: Noctuidae), fall armyworm [Spodoptera frugiperda (J.E. Smith)] (Lepidoptera: Noctuidae), and beet armyworm [Spodoptera exigua (Hübner)] to develop and reproduce on hemp was investigated in this study. Insects were reared on two hemp varieties, Maverick and Pipeline, as well as documented host plants soybean [Glycine max (L.) Merr.] (Fabales: Fabaceae) variety UA5414RR and cowpea [Vigna unguiculata (L.)] (Fabales: Fabaceae) variety Quickpick Pinkeye. Larvae of all three species reared on 'Maverick' had significantly faster preadult developmental times compared to the other hosts. Chrysodeixis includens larvae fed excised leaves of 'Maverick' and 'Pipeline' experienced higher intrinsic and finite rates of increase, higher net reproductive rates, and faster mean generation and doubling times. Spodoptera frugiperda larvae reared on 'Maverick', 'Pipeline', and 'UA5414RR' had higher intrinsic and finite rates of increase, higher net reproductive rates, and faster mean generation and doubling times compared to 'Quickpick Pinkeye'. Spodoptera exigua larvae had the highest survivorship on 'Maverick' and similar, positive lifetable statistics when reared on 'Maverick' and 'Pipeline'. The results of this study indicate hemp is an alternative host plant that has the potential to influence the population dynamics of C. includens, S. frugiperda, and S. exigua in Louisiana agroecosystems they co-occur in.

Life History of Chrysodeixis includens (Lepidoptera: Noctuidae) on Positively Charged Zein Nanoparticles

Research indicates that nanoparticles can be an effective agricultural pest management tool, though unintended effects on the insect must be evaluated before their use in agroecosystems. Chrysodeixis includens (Walker) was used as a model to evaluate chronic parental and generational exposure to empty, positively charged zein nanoparticles ((+)ZNP) and methoxyfenozide-loaded zein nanoparticles (+)ZNP(MFZ) at low-lethal concentrations. To determine concentration limits, an acute toxic response test on meridic diet evaluated (+)ZNP(MFZ) and technical grade methoxyfenozide using two diet assay techniques. No differences in acute toxicity were observed between the two treatments within their respective bioassays. With these results, population dynamics following chronic exposure to low-lethal concentrations were evaluated. Parental lifetables evaluated cohorts of C. includens reared on diet treated with LC5 equivalents of (+)ZNP, (+)ZNP(MFZ), or technical grade methoxyfenozide. Compared to technical grade methoxyfenozide, (+)ZNP(MFZ) lowered both the net reproductive rate and intrinsic rate of increase, and was more deleterious to C. includens throughout its lifespan. This was contrasted to (+)ZNP, which showed no differences in population dynamics when compared with the control. To evaluate chronic exposure to (+)ZNP, generational lifetables reared cohorts of C. includens on LC5 equivalent values of (+)ZNP and then took the resulting offspring to be reared on either (+)ZNP or untreated diet. No differences in lifetable statistics were observed between the two treatments, suggesting that (+)ZNP at low ppm do not induce toxic generational effects. This study provides evidence into the effects of nanodelivered methoxyfenozide and the generational impact of (+)ZNP.

Belowground Herbivory to Sweetpotato by Sweetpotato Weevil (Coleoptera: Brentidae) Alters Population Dynamics and Probing Behavior of Aboveground Herbivores

Aboveground and belowground herbivory can alter host quality and trophic interactions. However, little research has explored the impacts of belowground herbivory on plant virus epidemiology. To understand this interaction in sweetpotato, Ipomoea batatas L. (Lam), we studied the impact of herbivory by sweetpotato weevil, Cylas formicarius elegantulus (Summers), to storage roots on vector herbivore, Myzus persicae (Sulzer), the green peach aphid, and Aphis gossypii Glover, the cotton aphid, feeding behavior (M. persicae and A. gossypii) and population dynamics (M. persicae only as A. gossypii does not colonize sweetpotato). In addition, a nonvector herbivore, Chrysodeixis includens (Walker), the soybean looper, weight gain was included for comparison. Infestations of sweetpotato weevil in storage roots reduced C. includens weight gain and M. persicae intrinsic rate of increase (rm), net reproductive rate (Ro), and finite rate of increase (λ) on aboveground portions of the plant. In probing behaviors related to nonpersistent virus spread (30 min trials), M. persicae probed less often, took longer to reach the first pd (potential drop), had shorter II-3 (intracellular subphase sap ingestion) durations, and had fewer archlets on plants infested with C. formicarius elegantulus. Total phloem duration did not differ between treatments, indicating that the lowered performance of M. persicae on infested plants was not due to discrepancies in probing duration. Results were less clear for A. gossypii. Thus, in sweetpotato, belowground herbivory can alter plant virus vector abundance and behavior. Understanding the mechanisms underlying these changes in behavior could improve plant virus vector integrated pest management.

Profile of commercialized aphicides on the survivorship and feeding behavior of the cotton aphid, Aphis gossypii

The cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae), is one of the most destructive agricultural pests due to photosynthate removal and horizontal transmission of plant viruses. Horizontal transmission of plant viruses by aphids occurs during distinct feeding behavioral events, such as probing for non-persistent viruses or phloem feeding for persistent viruses. We employed toxicity bioassays and electrical penetration graph (EPG) methodology to compare toxicity and quantify changes to feeding behavior and toxicity of A. gossypii after exposure to commercialized aphicides. Commercialized aphicides containing flupyradifurone, sulfoxaflor, thiamethoxam, thiamethoxam + lambda cyhalothrin, and bifenthrin induced >90% aphid mortality within 4 h of exposure. Flupyradifurone was the most acutely toxic aphicide studied with an LT₅₀ of 8.9 min after exposure, which was approximately 3-fold lower than bifenthrin and thiamethoxam + lambda cyhalothrin. This was supported by our EPG results that showed a significant reduction in the proportion of aphids that continued to probe on cotton 4 h after exposure to flonicamid, thiamethoxam, flupyradifurone, bifenthrin, and thiamethoxam + lambda cyhalothrin. The commercialized aphicides containing spirotetramat, flonicamid, thiamethoxam, flupyradifurone, bifenthrin, sulfoxaflor, and pymetrozine significantly (P < 0.05) decreased the time to first probe when compared to the untreated control. Lastly, E1 (phloem salivation) and E2 (phloem ingestion) waveforms were significantly (P < 0.05) reduced for flupyradifurone, flonicamid, thiamethoxam, sulfoxaflor, and thiamethoxam. These data provide a comparative study for the development of new aphicides aiming to induce acute lethality and reduce aphid transmission of plant viruses.

Zein and lignin-based nanoparticles as soybean seed treatment: translocation and impact on seed and plant health

Zein nanoparticles (ZNPs) were synthesized with a cationic surfactant, didodecyldimethylammonium bromide (122.9 ± 0.8 nm, + 59.7 ± 4.4 mV) and a non-ionic surfactant, Tween 80 (118.7 ± 1.7 nm, + 26.4 ± 1.1 mV). Lignin-graft-poly(lactic-co-glycolic) acid nanoparticles (LNPs) were made without surfactants (52.9 ± 0.2 nm, − 54.9 ± 0.5 mV). Both samples were applied as antifungal seed treatments on soybeans, and their impact on germination and plant health was assessed. Treated seeds showed high germination rates (> 90% for all treatment groups), similar to the control group (100%). Root and stem lengths and the dry biomass of treated seeds were not statistically distinguishable from the control. Foliage from seed-treated plants was fed to larvae of Chrysodeixis includens with no differences in mortality between treatments. No translocation of fluorescently tagged particles was observed with fluorescence microscopy following seed treatment and germination. Nano-delivered azoxystrobin provided ~ 100% protection when LNPs were used. Results suggest ZNPs and LNPs are safe and effective delivery systems of active compounds for seed treatments.

Predator-Pest Dynamics of Arthropods Residing in Louisiana Soybean Agroecosystems

Simple Summary

Soybean agroecosystems in the Midsouth support an assorted insect community. Louisiana soybean is heavily managed by growers, and the subsequent effect on residing arthropod populations is not well understood. For sustainable management of soybean, evaluations need not only focus on problematic pests, but also the resident natural enemies. This study addresses the compositional and temporal abundance of prominent insects in Louisiana soybean, both pest and beneficial. Pest and natural enemy populations were monitored to delineate potential associations. We found that the pest community was dominated by those that fed on soybean through piercing-sucking mouthparts. Predator populations were comprised mainly of spiders and big-eyed bugs. Pest and predator populations were similarly more abundant later in the soybean reproductive period. A moderate positive linear relationship was observed between pest and predator communities indicating a temporal correlation. Here we present essential information about the pest and natural enemy communities residing in Louisiana.

Abstract

Over the past two decades, management practices within Louisiana soybean production have shifted. Successful application of an integrated pest management (IPM) strategy requires an understanding of how these changes have affected predator-pest dynamics. Surveys monitoring foliage-foraging arthropod populations in soybean took place across six locations within Louisiana over six years (2012–2014 and 2015–2018). Temporal associations of pest groups, defoliating and piercing-sucking, and predator groups relating to soybean phenology were observed. Additionally, soybean maturity groups (III, IV, and V) were also evaluated to delineate potential differences. Results indicated higher abundances of piercing-sucking pests compared to defoliating pests across both datasets (2012–2014 and 2015–2018). Pest groups were more abundant in later soybean reproductive periods, mainly attributed to Chrysodeixis includens and Piezodorus guildinii. Predator populations were mainly comprised of Araneae and Geocoridae throughout the survey periods. From 2015 to 2018, soybean growth had a significant effect on total predator abundance with more predators present at the pod-fill and soybean maturity stage. Correlations between total pest abundance and total predators exhibited a moderate positive linear relationship. Soybean maturity groups only influenced piercing-sucking pest abundance, with later maturing groups (IV and V) having higher numbers. Thus, control tools and tactics aimed at controlling late season pests should be modified to avoid reducing predator populations.

The role of diet quality and dietary patterns in predicting muscle mass and function in men over a 15-year period

A growing body of evidence suggests that diet quality may predict muscle health. This study found that a "Traditional" dietary pattern predicted greater muscle mass, and an anti-inflammatory diet predicted greater muscle mass and better muscle function over 15 years. These findings reinforce the importance of optimising dietary behaviours for healthy ageing.

INTRODUCTION

Research investigating the roles of individual nutrients in muscle health fails to account for the synergistic relationships between foods and nutrients. This study aimed to investigate the predictive value of diet quality and dietary patterns for muscle mass and function in men over a 15-year period.

METHODS

This longitudinal study was conducted in 522 men from the Geelong Osteoporosis Study with complete dietary and muscle mass or muscle function data at both baseline and 15-year follow-up assessments. Dietary exposures were extracted from food frequency questionnaires and included the Australian Recommended Food Score, the Dietary Inflammatory Index (DII®), and three a posteriori dietary patterns: Plant-focused, Western, and Traditional (Anglo-Australian). Outcome variables included dual-energy X-ray absorptiometry-derived skeletal muscle index (SMI) and muscle function measured with the timed up-and-go (TUG) test.

RESULTS

An anti-inflammatory diet and higher scores on a Traditional dietary pattern both predicted greater SMI ((B: -0.04 (95%CI -0.08, -0.00) kg/m²) and (B: 0.12 (95%CI 0.04, 0.20) kg/m²), respectively), while a pro-inflammatory diet predicted slower TUG (B: 0.11 (95%CI 0.001, 0.21) sec) over the 15-year follow-up period. These associations remained significant following adjustment for confounding variables. There were no associations observed for other dietary exposures.

CONCLUSION

A Traditional dietary pattern higher in vegetables, wholegrain cereals, and animal protein was associated with greater skeletal muscle mass, and an anti-inflammatory diet, also rich in vegetables, fruit, and wholegrain cereals, was associated with greater skeletal muscle mass and better muscle function over 15 years.

Effects of engineered lignin-graft-PLGA and zein-based nanoparticles on soybean health

The majority of published research on the effect of engineered nanoparticles on terrestrial plant species is focused on inorganic nanoparticles, with the effects of organic polymeric nanoparticles (NP) on plants remaining largely unexplored. It is critical to understand the impact of polymeric NPs on plants if these particles are to be used as agrochemical delivery systems. This study investigates the effect of biodegradable polymeric lignin-based nanoparticles (LNPs) and zein nanoparticles (ZNP) on soybean plant health. The LNPs (114 ± 3.4 nm, -53.8 ± 6.9 mV) were synthesized by emulsion evaporation from lignin-graft-poly(lactic-co-glycolic) acid, and ZNPs (142 ± 3.9 nm and + 64.5 ± 4.7 mV) were synthesized by nanoprecipitation. Soybeans were grown hydroponically and treated with 0.02, 0.2, and 2 mg/ml of LNPs or ZNPs at 28 days after germination. Plants were harvested after 1, 3, 7 and 14 days of particle exposure and analyzed for root and stem length, chlorophyll concentration, dry biomass of roots and stem, nutrient uptake and plant ROS. Root and stem length, chlorophyll and stem biomass did not differ significantly between treatments and controls for LNPs-treated plants at all concentrations, and at low doses of ZNPs. At 2 mg/ml ZNPs, the highest concentration tested, after 7 days of treatment chlorophyll levels and root biomass increased and stem length was reduced in comparison to the control. Nutrient uptake was largely unaffected at 0.02 and 0.2 mg/ml NPs. A concentration-dependent increase in the oxidative stresss was detected, especially in the ZNP treated plants. Overall, LNPs and ZNPs had a minimum impact on soybean health especially at low and medium doses. To our knowledge this is the first study to show the effect of zein and lignin based polymeric NPs designed for agrochemical delivery on soybean plant health.

Multidimensional analysis of excitonic spectra of monolayers of tungsten disulphide: toward computer-aided identification of structural and environmental perturbations of 2D materials

Despite 2D materials holding great promise for a broad range of applications, the proliferation of devices and their fulfillment of real-life demands are still far from being realized. Experimentally obtainable samples commonly experience a wide range of perturbations (ripples and wrinkles, point and line defects, grain boundaries, strain field, doping, water intercalation, oxidation, edge reconstructions) significantly deviating the properties from idealistic models. These perturbations, in general, can be entangled or occur in groups with each group forming a complex perturbation making the interpretations of observable physical properties and the disentanglement of simultaneously acting effects a highly non-trivial task even for an experienced researcher. Here we generalise statistical correlation analysis of excitonic spectra of monolayer WS2, acquired by hyperspectral absorption and photoluminescence imaging, to a multidimensional case, and examine multidimensional correlations via unsupervised machine learning algorithms. Using principal component analysis we are able to identify four dominant components that are correlated with tensile strain, disorder induced by adsorption or intercalation of environmental molecules, multi-layer regions and charge doping, respectively. This approach has the potential to determine the local environment of WS2 monolayers or other 2D materials from simple optical measurements, and paves the way toward advanced, machine-aided, characterization of monolayer matter.

Sugarcane Aphid (Hemiptera: Aphididae) on Sorghum. I. Population Characteristics and Dispersion Patterns in Relation to Different Sample Unit Sizes

The sugarcane aphid, Melanaphis sacchari (Zehntner), has emerged as a serious pest of sorghum in the United States. Field trials were conducted in Louisiana and South Carolina in 2016-2018 to investigate its population characteristics and distribution patterns in relation to four sample unit sizes (three circular and one leaf based). Sugarcane aphid populations usually progressed through a phase of rapid rise followed by a phase of rapid decline within a span of 5-6 wk, with peak density determined by sorghum cultivars and climatic conditions. Peak population densities for susceptible cultivars were 1.9-14.9× that for resistant cultivars on a per plant basis. Melanaphis sacchari tended to concentrate on the lower green leaf nodes early in the infestation, with the distribution shifting toward higher green leaf nodes as the infestation progressed. Aphid densities per cm2 at the basal and middle sections were about twice as high as at the distal section of leaves. The proportions of infested sample units were fitted to the Wilson-Room binomial model that incorporates the effect of density on clumping pattern. For a specific sample unit size, clumping patterns were similar across cultivars, years, and leaf positions, but varied across infestation stages. For a fixed aphid density per sample unit, the proportion of infested sample units decreased with increasing sample unit size. For a fixed aphid density per cm2, proportion infested increased with increasing sample unit size, indicating less clumping with a larger sample unit size. Field sampling time and efficiency between samplers were quantified.

Characterizing Host Plant Resistance to Melanaphis sacchari (Hemiptera: Aphididae) in Selected Sorghum Plant Introductions

Since 2013 Melanaphis sacchari (Zehnter) (Hemiptera: Aphididae), the sugarcane aphid, has been a threat to sorghum production in the United States. The development of resistant sorghum hybrids has been one of the main management strategies. However, plant resistance can be overcome over time and new resistance genes need to be identified and introduced into adapted sorghum hybrids to secure sorghum production. Sorghum plant introduction (PI) genotypes were screened for resistance to M. sacchari through laboratory, greenhouse, and field assays. In addition, the feeding parameters of M. saccahri were analyzed and detailed in seven sorghum genotypes through EPG assays. Results showed sorghum genotypes PI 524770, PI 564163, and PI 643515 expressed resistance to M. sacchari consistently in laboratory, greenhouse, and field tests. EPG analysis suggested sorghum genotypes PI 524770 and PI 564163 express antibiosis to M. sacchari while PI 643515 expresses both antibiosis and antixenosis. Increasing the number of sorghum hybrids resistant to M. sacchari is key to improving integrated pest management of M. sacchari. By utilizing host plant resistance, sorghum producers can decrease insecticide applications while enhancing biological control.

Study of the X-ray radiation interaction with a multislit collimator for the creation of microbeams in radiation therapy

Microbeam radiation therapy (MRT) is a developing radiotherapy, based on the use of beams only a few tens of micrometres wide, generated by synchrotron X-ray sources. The spatial fractionation of the homogeneous beam into an array of microbeams is possible using a multislit collimator (MSC), i.e. a machined metal block with regular apertures. Dosimetry in MRT is challenging and previous works still show differences between calculated and experimental dose profiles of 10-30%, which are not acceptable for a clinical implementation of treatment. The interaction of the X-rays with the MSC may contribute to the observed discrepancies; the present study therefore investigates the dose contribution due to radiation interaction with the MSC inner walls and radiation leakage of the MSC. Dose distributions inside a water-equivalent phantom were evaluated for different field sizes and three typical spectra used for MRT studies at the European Synchrotron Biomedical beamline ID17. Film dosimetry was utilized to determine the contribution of radiation interaction with the MSC inner walls; Monte Carlo simulations were implemented to calculate the radiation leakage contribution. Both factors turned out to be relevant for the dose deposition, especially for small fields. Photons interacting with the MSC walls may bring up to 16% more dose in the valley regions, between the microbeams. Depending on the chosen spectrum, the radiation leakage close to the phantom surface can contribute up to 50% of the valley dose for a 5 mm × 5 mm field. The current study underlines that a detailed characterization of the MSC must be performed systematically and accurate MRT dosimetry protocols must include the contribution of radiation leakage and radiation interaction with the MSC in order to avoid significant errors in the dose evaluation at the micrometric scale.

Elucidating Efficacy of Ingested Positively Charged Zein Nanoparticles Against Noctuidae

A meridic diet overlay bioassay using empty, positively charged zein nanoparticles ((+)ZNP) was performed on soybean looper (Chrysodeixis includens (Walker)), tobacco budworm (Heliothis virescens (F.)), and velvetbean caterpillar (Anticarsia gemmatalis Hübner) (Lepidoptera: Noctuidae). Assessment of effects on mortality and development weights 7 d after ingestion of (+)ZNP were evaluated on larvae of each species. Treatments involved different concentrations, with H. virescens and A. gemmatalis offered 0 and 3,800 ppm (+)ZNP, whereas C. includens colonies were offered 0, 630, 1,260, and 2,520 ppm (+)ZNP. Mortality of A. gemmatalis and C. includens increased after ingestion of the highest (+)ZNP concentrations, while H. virescens neonate mortality was unaffected. Neonate and third-instar weights of A. gemmatalis and C. includens, and neonate H. virescens, decreased with high (+)ZNP concentrations. Following mortality results from A. gemmatalis neonates, a concentration response test was performed using a range of (+)ZNP concentrations. The LC50 for A. gemmatalis was 1,478 ppm. The potential of (+)ZNP as a pest management tactic is discussed.

Evaluating Behavioral Responses of Selected Stink Bugs (Hemiptera: Pentatomidae) to Spinosad

Southern green stink bug, Nezara viridula (L.) and redbanded stink bug, Piezodorus guildinii (Westwood) are two of the most important seed sucking pests affecting Louisiana soybean production and rice stink bug, Oebalus pugnax (F.) is an important late season pest in Louisiana rice. Exploration of chemicals that exhibit attraction or repellent activities toward major stink bug species would be beneficial in developing push-pull strategies. Spinosad is a commercially available natural insecticide that may have arrestant, attractant, or phagostimulant properties against stink bugs. To test this, a series of laboratory experiments were conducted to investigate the tactile, olfactory, and feeding responses of these stink bugs toward two commercial spinosad products (Entrust and Tracer) and technical grade spinosad. In tactile assays, female and male redbanded stink bug were arrested by Entrust, Tracer, and technical grade spinosad, whereas only rice stink bug and southern green stink bug males were arrested by Entrust. Y-tube assays revealed no attraction to any of the products by either male or female rice stink bug, redbanded stink bug, or southern green stink bug. In paired (treated or untreated soybean seed) feeding preference experiments, southern green stink bug showed no preference for any treatment, whereas redbanded stink bug fed more on Entrust- and Tracer-treated seed. From these results, spinosad appears to have an arrestant and phagostimulant effect on redbanded stink bug in the laboratory.

In-phase sub-Nyquist lenslet arrays encoded onto spatial light modulators

When encoding diffractive lenses onto a spatial light modulator (SLM), there is a Nyquist limit to the smallest focal length that can be formed. When this limit is surpassed, a two-dimensional array of lenslets is formed. There have been very few discussions on the performance of these lenslets. In this work, we focus on the phase distribution of these lenses in the array. We show that, for certain values of the focal length, the lenslets are all in perfect phase. We show that this situation happens for a total number of N/4 different discrete equidistant sub-Nyquist focal lengths, where N×N is the number of pixels in the SLM. We find other distances in between where the array is composed of two sets of lenslets with a relative π phase among them. Finally, we illustrate these phase distributions in the application to generate an array of vortex producing lenses. We expect that these results might be useful for high-accuracy interferometric or multiple imaging where this phase must be exactly the same for each replica.

Influence of Sorghum Cultivar, Nitrogen Fertilization, and Insecticides on Infestations of the Sugarcane Aphid (Hemiptera: Aphididae) in the Southern United States

The sugarcane aphid, Melanaphis sacchari Zehntner, is an economically damaging pest of sorghum, Sorghum bicolor (L.), across the southern United States. Field experiments investigated impacts of sorghum cultivar, nitrogen fertilization, and insecticides on M. sacchari infestations and sorghum yields in Louisiana and South Carolina in 2017 and 2018. In South Carolina, M. sacchari densities in unprotected plots peaked on 30-31 July of both years before declining by early- to mid-August. In Louisiana, infestations peaked on 26 and 12 July for 2017 and 2018, respectively, and declined by mid-August. Nitrogen fertilization influenced M. sacchari densities in Louisiana in 2018 with the highest-level infestations recorded from plots that received high N rates. Densities of M. sacchari on susceptible sorghum cultivar, DKS 38-88, were 1.5- to 2.3-fold greater than on DKS 37-07 in both years in Louisiana and in 2018 in South Carolina. Nitrogen fertilization was associated with improved sorghum yields in Louisiana experiments. Sorghum yields across experiments were 2- to 4-fold greater in plots protected with multiple insecticide applications than in unprotected plots. Yield from plots with insecticides sprayed once at currently used action thresholds differed from unprotected plots only in the 2018 Louisiana experiment. Results from these experiments indicate insecticidal protection of susceptible sorghum cultivars remains critical throughout much of the southern United States. Further research is needed to develop integrated management programs that incorporate fertilization manipulation, cultivar resistance, and insecticidal control.

Supertransport of excitons in atomically thin organic semiconductors at the 2D quantum limit

Long-range and fast transport of coherent excitons is important for the development of high-speed excitonic circuits and quantum computing applications. However, most of these coherent excitons have only been observed in some low-dimensional semiconductors when coupled with cavities, as there are large inhomogeneous broadening and dephasing effects on the transport of excitons in their native states in materials. Here, by confining coherent excitons at the 2D quantum limit, we first observed molecular aggregation-enabled 'supertransport' of excitons in atomically thin two-dimensional (2D) organic semiconductors between coherent states, with a measured high effective exciton diffusion coefficient of ~346.9 cm2/s at room temperature. This value is one to several orders of magnitude higher than the values reported for other organic molecular aggregates and low-dimensional inorganic materials. Without coupling to any optical cavities, the monolayer pentacene sample, a very clean 2D quantum system (~1.2 nm thick) with high crystallinity (J-type aggregation) and minimal interfacial states, showed superradiant emission from Frenkel excitons, which was experimentally confirmed by the temperature-dependent photoluminescence (PL) emission, highly enhanced radiative decay rate, significantly narrowed PL peak width and strongly directional in-plane emission. The coherence in monolayer pentacene samples was observed to be delocalised over ~135 molecules, which is significantly larger than the values (a few molecules) observed for other organic thin films. In addition, the supertransport of excitons in monolayer pentacene samples showed highly anisotropic behaviour. Our results pave the way for the development of future high-speed excitonic circuits, fast OLEDs, and other optoelectronic devices.

Detailed Characterization of Melanaphis sacchari (Hemiptera: Aphididae) Feeding Behavior on Different Host Plants

Worldwide, Melanaphis sacchari Zehntner is reported on several plants in the family Poaceae, including important crops. In the United States, M. sacchari has been present primarily on sugarcane (Saccharum officinarum L.), but recently sorghum (Sorghum bicolor (L.) Moench) has become a main host. It is not clear how M. sacchari exploits sorghum or other plant species present in the Louisiana agro-ecoscape, but there is potential for these plants to be bridging hosts. Thus, this study determined the feeding behavior of M. sacchari on sorghum, rice, Oryza sativa (L.), sweetpotato, Ipomea batatas (L.), maize, Zea mays (L.), Johnsongrass, S. halepense (L.), and wheat Triticum aestivum (L.) using electrical penetration graphs. Melanaphis sacchari established sustained feeding on sorghum, Johnsongrass, wheat, and rice, only a negligent percentage on maize and no aphid fed on sweetpotato. Differences in Electrical Penetration Graph parameters among the plants in nonpenetrating total time and the lower number of probes, time to penetration initiation, proportion of individuals probing, number of probes shorter than 30 s, number of probes longer than 30 s but shorter than 3 min, pathway phase duration, and number of cell punctures during pathway phase, suggest epidermis and mesophyll factors affecting aphid feeding behavior. While the lack of differences in number of feeding occurrences, total time feeding, and number of sustained feeding occurrences shows that M. sacchari is able to feed on those plants, sieve element factors such as resistance or low nutritional quality prevent the growth of this population in field.

The Lipid Flippases ALA4 and ALA5 Play Critical Roles in Cell Expansion and Plant Growth

Aminophospholipid ATPases (ALAs) are lipid flippases involved in transporting specific lipids across membrane bilayers. Arabidopsis (Arabidopsis thaliana) contains 12 ALAs in five phylogenetic clusters, including four in cluster 3 (ALA4-ALA7). ALA4/5 and ALA6/7, are expressed primarily in vegetative tissues and pollen, respectively. Previously, a double knockout of ALA6/7 was shown to result in pollen fertility defects. Here we show that a double knockout of ALA4/5 results in dwarfism, characterized by reduced growth in rosettes (6.5-fold), roots (4.3-fold), bolts (4.5-fold), and hypocotyls (2-fold). Reduced cell size was observed for multiple vegetative cell types, suggesting a role for ALA4/5 in cellular expansion. Members of the third ALA cluster are at least partially interchangeable, as transgenes expressing ALA6 in vegetative tissues partially rescued ala4/5 mutant phenotypes, and expression of ALA4 transgenes in pollen fully rescued ala6/7 mutant fertility defects. ALA4-GFP displayed plasma membrane and endomembrane localization patterns when imaged in both guard cells and pollen. Lipid profiling revealed ala4/5 rosettes had perturbations in glycerolipid and sphingolipid content. Assays in yeast revealed that ALA5 can flip a variety of glycerolipids and the sphingolipid sphingomyelin across membranes. These results support a model whereby the flippase activity of ALA4 and ALA5 impacts the homeostasis of both glycerolipids and sphingolipids and is important for cellular expansion during vegetative growth.

Persistent coherence of quantum superpositions in an optimally doped cuprate revealed by 2D spectroscopy

Quantum materials displaying intriguing magnetic and electronic properties could be key to the development of future technologies. However, it is poorly understood how the macroscopic behavior emerges in complex materials with strong electronic correlations. While measurements of the dynamics of excited electronic populations have been able to give some insight, they have largely neglected the intricate dynamics of quantum coherence. Here, we apply multidimensional coherent spectroscopy to a prototypical cuprate and report unprecedented coherent dynamics persisting for ~500 fs, originating directly from the quantum superposition of optically excited states separated by 20 to 60 meV. These results reveal that the states in this energy range are correlated with the optically excited states at ~1.5 eV and point to nontrivial interactions between quantum many-body states on the different energy scales. In revealing these dynamics and correlations, we demonstrate that multidimensional coherent spectroscopy can interrogate complex quantum materials in unprecedented ways.

Chemical inhibition of Kir channels reduces salivary secretions and phloem feeding of the cotton aphid, Aphis gossypii (Glover)

BACKGROUND

The unique feeding biology of aphids suggests novel insecticide targets are likely to exist outside of the nervous system. We therefore aimed to directly test the hypothesis that pharmacological inhibition of inward rectifier potassium (Kir) channels would result in salivary gland failure and reduced sap ingestion by the cotton aphid, Aphis gossypii.

RESULTS

The Kir inhibitors VU041 and VU590 reduced the length of the salivary sheath in a concentration dependent manner, indicating that the secretory activity of the salivary gland is reduced by Kir inhibition. Next, we employed the electrical penetration graph (EPG) technique to measure the impact Kir inhibition has to aphid sap feeding and feeding biology. Data show that foliar application of VU041 eliminated the E1 and E2 phases (phloem feeding) in all aphids studied. Contact exposure to VU041 after foliar applications was found to be toxic to A. gossypii at 72 and 96 h post-infestation, indicating mortality is likely a result of starvation and not acute toxicity. Furthermore, VU041 exposure significantly altered the feeding behavior of aphids, which is toxicologically relevant for plant-virus interactions.

CONCLUSION

These data suggest Kir channels are critical for proper function of aphid salivary glands and the reduced plant feeding justifies future work in developing salivary gland Kir channels as novel mechanism aphicides. Furthermore, products like VU041 would add to a very minor arsenal of compounds that simultaneously reduce vector abundance and alter feeding behavior. © 2019 Society of Chemical Industry.

The optical properties of Cs4PbBr6-CsPbBr3 perovskite composites

Although the optoelectronic applications of metal halide perovskites have been intensively investigated in recent years, the fundamental carrier dynamics of zero-dimensional (0D) Cs4PbBr6 perovskites has been relatively underexplored; in particular, the nature of the green fluorescence is highly debated. Nevertheless, the unique photophysical properties are of immense interest for a variety of potential applications. In this work, the green emission of the CsPbBr3-Cs4PbBr6 perovskite composites is studied using temperature dependent photoluminescence (PL). The PL spectra at different temperatures simultaneously contain two sub-peaks (520 nm and 550 nm), which are ascribed to the emissions of the band-edge and the defect trapped exciton of CsPbBr3. This finding will help to understand the controversial photoluminescence currently observed in different 0D Cs4PbBr6 perovskites.

Determining Potential Hosts of Melanaphis sacchari (Hemiptera: Aphididae) in the Louisiana Agroecoscape

Although Melanaphis sacchari Zehntner (Hemiptera: Aphididae) is known worldwide for its injury to sugarcane, Saccharum officinarum L., and sorghum, Sorghum bicolor (L.) Moench, M. sacchari is reported to infest several plants in the family Poaceae, including important agronomic crops. It is not clear how M. sacchari interacts with other crops in the Louisiana agroecoscape but there is potential for these plants to be bridging hosts prior to sorghum colonization. Thus, this study determined the population dynamics of M. sacchari on sugarcane, sorghum, rice (Oryza sativa L.), sweetpotato (Ipomea batatas L.), maize (Zea mays L.), Johnsongrass (S. halepense L.), and wheat (Triticum aestivum L.) using life table studies. Melanaphis sacchari was able to complete its life cycle on sorghum, sugarcane, rice, and wheat, having the highest intrinsic rate of increase (rm) on sorghum (0.466). Population growth was negative on rice (rm = -0.020) and intermediately positive on sugarcane and Johnsongrass. The results demonstrate that there is the potential for multiple host use within the agricultural landscape. Using the information collected from this study, population estimations on host plants demonstrate that M. sacchari populations will increase more rapidly on sorghum than on the other host plants.

Encoding lenses with focal lengths lower than the Nyquist limit using high phase-modulation displays

Liquid crystal displays allow the easy implementation of diffractive optical elements. However, the shortest focal lengths for lenses are limited by Nyquist conditions. In this work, we show that focal lengths much lower than this Nyquist limit can be encoded onto devices having a large phase-dynamic range. Experimental results are included with a display showing 10π phase modulation reducing the Nyquist limit by a factor of about 1/10.

Simulation of multimode optical fibers using the angular spectrum algorithm and a Fourier analysis

Multimode optical fibers are gaining increased interest for higher data rate transmissions. In this work, we examine the propagation of beams in multimode optical fibers using the angular spectrum method for several values for the propagation constant V. We prepare a sequence of 4096 images over 200,000 steps, each representing a wavelength within the fiber. We perform a one-dimensional Fourier transform of these data and obtain the propagation constant for each transmitted mode. We then obtain the electric field profile for each transmitted mode. We find excellent agreement with weakly guided mode theory. This work represents another step in the use of this algorithm for analyzing more complicated optical fiber structures.

Gouy phase effects on propagation of pure and hybrid vector beams

The robustness of the polarization spatial distribution of vector beams upon propagation is crucial for a number of applications, including optical communications and materials processing. This study has been commonly centered on Gouy phase effects on focused vector beams. In this work, we present a theoretical and experimental analysis of the Gouy phase's effects on the propagation of pure and hybrid vector beams. Experimental results at various axial planes, before and past the focus, are obtained by using a simplified liquid-crystal spatial light modulator-based optical system that allows the easy generation of these beams. Furthermore, a new alternative optical set-up that is devoid of moving elements is demonstrated, which simplifies this study. We experimentally verify the differences between pure and hybrid vector beams upon propagation. While the first ones remain stable, hybrid vector beams show Gouy phase effects that demonstrate an optical activity where the local polarization states rotate by an angle that depends on the propagation distance. Experimental results agree with the theory.

Status of Stink Bug (Hemiptera: Pentatomidae) Egg Parasitoids in Soybeans in Louisiana

Stink bugs are important insect pests of soybean, Glycine max (L.), in Louisiana. Scouting, economic thresholds, and insecticide applications are the main strategies used in the integrated pest management of soybean insect pests. However, biological control of stink bug eggs by parasitoids has the potential to reduce populations of these pests. A survey of stink bug egg parasitoids was conducted at different sites in Louisiana from 2008 to 2010. Similarly, a study on the incidence of stink bug egg parasitoids within soybean vertical strata and plant structures was conducted in 2009 to 2011. Species of stink bug eggs collected during the studies included the redbanded stink bug, Piezodorus guildinii (Westwood), the brown stink bug species complex, Euschistus spp., the southern green stink bug, Nezara viridula L., the spined soldier bug, Podisus maculiventris (Say), and the green stink bug, Chinavia hilaris (Say). The percentage of stink bug eggs parasitized in the central location of Louisiana was higher compared with the northwest location during the 2008 to 2010 growing seasons. There were no differences in percentage of stink bug egg parasitism within soybean plant strata between 2009 and 2011. Telenomus podisi Ashmead (Hymenoptera: Platygastridae) was the most abundant parasitoid, and it showed preference for P. guildinii. Other platygastrid species that emerged included Trissolcus euschisti Ashmead (Hymenoptera: Platygastridae), Gryon obesum Masner (Hymenoptera: Platygastridae), and Telenomus longicornis Johnson (Hymenoptera: Platygastridae). This study is the first to report the parasitization of P. guildinii eggs on soybeans in the United States.

Effects of Potassium Fertilizer Rates on Soybean Looper (Lepidoptera: Noctuidae) Development

Potassium (K) has an important impact on physiological and biochemical processes in plants. Soybean, Glycine max (L.) Merrill, requires high K availability for optimal yield. However, changes in nutrient availability in plants may also affect herbivore population size and/or development. Soybean looper, Chrysodeixis includens (Walker) (Lepidoptera: Noctuidae), is one of the most destructive pests of soybean in the southern United States. In this study, we evaluated the effects of different K fertilization rates on soybean looper development, soybean seed weight, and soybean seed nutritional quality. Soybean plants were supplied with six different rates of K fertilizer (0, 33.6, 67.3, 100.9, 134.5, and 168.1 kg/ha as K2O). Soybean leaves were sampled at R1, R3, R5, and R6 stages and fed to soybean looper in laboratory bioassays. Soybean looper mortality, fecundity, and fertility were not significantly affected by feeding on leaf tissues of soybean treated with different potassium fertilizer rates. However, soybean looper consumed more leaf tissue and spent less time completing larval development when fed on foliage from treatments of 134.5 and 168.1 kg/ha. Pupal weight significantly increased at 134.5 and 168.1 kg/ha. There was no significant difference in percentage of protein, oil, and fiber in soybean seeds among six K fertilizer rates. Percentage of K in soybean seeds and 100 seed weight were significantly enhanced at 168.1 kg/ha. Nitrogen (N) content of foliage was not affected by applying K fertilizer at different rates. Our results indicate that higher K fertilizer rates can enhance soybean seed weight but also facilitate soybean looper development.

Preference of the Redbanded Stink Bug (Hemiptera: Pentatomidae) for Selected Spring Host Plants

The redbanded stink bug, Piezodorus guildinii (Westwood), has emerged as a major stink bug pest of soybean in Louisiana during the last decade. In the spring, this species is usually found in leguminous hosts where populations can build up before migrating to soybean fields in the summer. However, studies looking at the preference of this species to the potential spring leguminous hosts under the natural conditions are lacking. Field studies were conducted in different geographical locations of Louisiana from 2013 to 2015 to evaluate preference of P. guildinii to six different leguminous cover crops: crimson clover, (Trifolium incarnatum L.), cardinal red clover, (Trifolium pratense L.), Austrian winter pea, (Pisum sativum L.), berseem clover, (Trifolium alexandrinum L.), hairy vetch, (Vicia villosa Roth), and white clover, (Trifolium repens L.). Our study showed that the odds of finding both adult and nymph P. guildinii was significantly higher in crimson clover followed by white clover, while the odds of finding both adult and nymph P. guildinii was significantly lower in other hosts. Therefore, crimson and white clovers are the preferred hosts as well as the important reproductive host plants of P. guildinii in the spring season.

Simulation of optical fiber couplers using the angular spectrum algorithm

We examine single-mode optical fiber transmission using the angular spectrum method. We find excellent agreement with the theoretical solutions for the cylindrical single-mode optical fiber. Next, we examine fiber coupler configurations with 1×2, 1×3, and 1×5 designs. The input within the central fiber core is broadcast equally into the surrounding fiber cores and then returns with propagation distances as expected. Then we examine supermode theory for the 1×3 case. The initial energy is sent into different combinations of fiber cores where their phase relationship governs the output. Surprisingly, we find evidence of an unexpected mode in some of the multicore designs. We expect these results might be useful for exploration of more complicated fiber core arrays. However, computational times are short using this algorithm.

Q-plates with a nonlinear azimuthal distribution of the principal axis: application to encoding binary data

We encode q-plates where the angular orientation of the principal axis is varied spatially with a nonstandard distribution. In the usual q-plate design, the orientation of the optical axis depends linearly on the azimuthal angle. In this work, we examine cases where this azimuthal dependence is nonlinear. We consider two cases: first, where the principal axis distribution is like an inverse-tangent function of the azimuth; and second, where it displays linear and flat segments. This last case is proposed as a new method for encoding binary data into the azimuthal lobes of the vector beam. We encode these patterns using a spatial light modulator system that allows new and exotic q-plate designs without the difficulty of fabricating individual plates. Experimental results are presented.

Cold Tolerance and Supercooling Capacity of the Redbanded Stink Bug (Hemiptera: Pentatomidae)

The redbanded stink bug Piezodorus guildinii (Westwood) (Hemiptera: Pentatomidae) is an invasive stink bug species in the United States. First documented as a soybean pest in Louisiana in the year 2000, this species continues to spread in the Mid-South region of the United States. We designed laboratory and field studies to investigate supercooling points, lethal exposure time (LT), critical thermal minimum (CTmin), and winter mortality of this species. The mean supercooling points (SCP) ± SE of adult field collected P. guildinii ranged from -8.3 ± 0.2°C (highest) in March to -11.0 ± 0.2°C (lowest) in January. Significant differences in SCP occurred over the months and between sexes with significant interactions between month and sex. The CTmin was significantly different between adults and nymphs (third, fourth, and fifth instars combined). LT50 and LT90 were evaluated at subzero temperatures of 0°C, -2°C, and -5°C. There were significant differences in LT50 and LT90 among the temperature treatments. Winter survival significantly differed between the two study years and decreased with progression of winter months.

Influence of Host Quality and Temperature on the Biology of Diaeretiella rapae (Hymenoptera: Braconidae, Aphidiinae)

Biological features of Diaeretiella rapae (McIntosh), an aphid parasitoid, are conditioned by temperature and host. However, studies of host quality changes due to temperature adaptability have not been performed previously. Therefore, this study evaluated the adaptability of Lipaphis pseudobrassicae (Davis) and Myzus persicae (Sulzer) to high temperature, high temperature effect on their quality as hosts for D. rapae, and on parasitoid's thermal threshold. Aphid development, survivorship, fecundity, and longevity were compared at 19 °C and 28 °C. Host quality in different temperatures was determined through evaluation of parasitoid biology. Thermal threshold of D. rapae was determined using development time data. At 28 °C, development time, rate of immature survival, and total fecundity rates were greater in L. pseudobrassicae than in M. persicae. Development time of D. rapae in L. pseudobrassicae was shorter than that in M. persicae at 28 °C and 31 °C for females and at 31 °C for males. The thermal threshold of D. rapae was 6.38 °C and 3.33 °C for females and 4.45 °C and 3.63 °C for males developed on L. pseudobrassicae and M. persicae, respectively. Diaeretiella rapae size gain was greater in L. pseudobrassicae than that in M. persicae at 25 °C and 28 °C. Lipaphis pseudobrassicae showed better adaptation than M. persicae to elevated temperatures, which resulted in a better quality host for D. rapae at temperatures of 28 °C and 31 °C and a higher lower thermal threshold when the parasitoid developed within L. pseudobrassicae. The host's adaptation to high temperatures is a determinant of host quality for the parasitoid at that same climatic condition.

Vector Beam Polarization State Spectrum Analyzer

We present a proof of concept for a vector beam polarization state spectrum analyzer based on the combination of a polarization diffraction grating (PDG) and an encoded harmonic q-plate grating (QPG). As a result, a two-dimensional polarization diffraction grating is formed that generates six different q-plate channels with topological charges from -3 to +3 in the horizontal direction, and each is split in the vertical direction into the six polarization channels at the cardinal points of the corresponding higher-order Poincaré sphere. Consequently, 36 different channels are generated in parallel. This special polarization diffractive element is experimentally demonstrated using a single phase-only spatial light modulator in a reflective optical architecture. Finally, we show that this system can be used as a vector beam polarization state spectrum analyzer, where both the topological charge and the state of polarization of an input vector beam can be simultaneously determined in a single experiment. We expect that these results would be useful for applications in optical communications.

Time-Domain THz Spectroscopy Reveals Coupled Protein-Hydration Dielectric Response in Solutions of Native and Fibrils of Human Lysozyme

Here we reveal details of the interaction between human lysozyme proteins, both native and fibrils, and their water environment by intense terahertz time domain spectroscopy. With the aid of a rigorous dielectric model, we determine the amplitude and phase of the oscillating dipole induced by the THz field in the volume containing the protein and its hydration water. At low concentrations, the amplitude of this induced dipolar response decreases with increasing concentration. Beyond a certain threshold, marking the onset of the interactions between the extended hydration shells, the amplitude remains fixed but the phase of the induced dipolar response, which is initially in phase with the applied THz field, begins to change. The changes observed in the THz response reveal protein-protein interactions mediated by extended hydration layers, which may control fibril formation and may have an important role in chemical recognition phenomena.

Bacteria Associated With Piezodorus guildinii (Hemiptera: Pentatomidae), With Special Reference to Those Transmitted by Feeding

The redbanded stink bug, Piezodorus guildinii (Westwood) (Hemiptera: Heteroptera: Pentatomidae), is a rapidly growing pest damaging southern US agriculture. Pentatomid stink bugs are known to vector bacterial, fungal, and viral plant diseases. However, bacteria associated with redbanded stink bugs and their vector potential have not yet been assessed. In this study, we 1) cultured and identified bacteria transmitted by feeding of redbanded stink bug and 2) described bacteria from guts of redbanded stink bug individuals using next-generation sequencing of 16S rRNA genes. Nineteen bacteria transmitted by feeding of redbanded stink bug on soybean agar were isolated and identified via Sanger sequencing of near full length 16S RNA genes. The transmitted bacteria belonged to at least a dozen species in eight genera and included potential plant pathogens (Phaseolibacter flectens), plant beneficials (Bacillus atropheus), and possible insect beneficials (Acinetobacter sp. and Citrobacter farmeri). A total of 284,448 reads were captured from Illumina MiSeq sequencing of the uncultured gut bacteria community. Fifty-one putative bacteria species (74% of the estimated total species richness) were identified via matches to NCBI databases. The bacteria metagenome contained potential plant and insect pathogens (Erwinia persicina, E. rhaponici, Brenneria nigrifluens, Ralstonia picketti, and Serratia marcescens) and beneficials (Pantoea dispersa, Klebsiella oxytoca, Clostridium butyricum, and Citrobacter farmeri).

Arithmetic with q-plates

In this work we show the capability to form various q-plate equivalent systems using combinations of commercially available q-plates. We show operations like changing the sign of the q-value, or the addition and subtraction of q-plates. These operations only require simple combinations of q-plates and half-wave plates. Experimental results are presented in all cases. Following this procedure, experimental testing of higher and negative q-valued devices can be carried out using commonly available q-valued devices.

Terahertz thermometry of gold nanospheres in water

The photo-thermal effects of plasmonic nanoparticles are promising for cancer therapies. These treatments would greatly benefit from real-time, multi-scale temperature mapping by non-invasive means. Here we show that intense terahertz time domain spectroscopy can be used as a non-contact and high-resolution thermometer of water solutions. Using this technique, we measure the temperature change, triggered by femtosecond amplified laser pulses, of a solution of gold nanospheres in water. Extensions of this ultra-fast and non-invasive technique could open the door to real-time micro-thermometry of single cells without fluorescent labels.

Hg concentrations in fish from coastal waters of California and Western North America

The State of California conducted an extensive and systematic survey of mercury (Hg) in fish from the California coast in 2009 and 2010. The California survey sampled 3483 fish representing 46 species at 68 locations, and demonstrated that methylHg in fish presents a widespread exposure risk to fish consumers. Most of the locations sampled (37 of 68) had a species with an average concentration above 0.3μg/gwet weight (ww), and 10 locations an average above 1.0μg/gww. The recent and robust dataset from California provided a basis for a broader examination of spatial and temporal patterns in fish Hg in coastal waters of Western North America. There is a striking lack of data in publicly accessible databases on Hg and other contaminants in coastal fish. An assessment of the raw data from these databases suggested the presence of relatively high concentrations along the California coast and in Puget Sound, and relatively low concentrations along the coasts of Alaska and Oregon, and the outer coast of Washington. The dataset suggests that Hg concentrations of public health concern can be observed at any location on the coast of Western North America where long-lived predator species are sampled. Output from a linear mixed-effects model resembled the spatial pattern observed for the raw data and suggested, based on the limited dataset, a lack of trend in fish Hg over the nearly 30-year period covered by the dataset. Expanded and continued monitoring, accompanied by rigorous data management procedures, would be of great value in characterizing methylHg exposure, and tracking changes in contamination of coastal fish in response to possible increases in atmospheric Hg emissions in Asia, climate change, and terrestrial Hg control efforts in coastal watersheds.

Revealing and Characterizing Dark Excitons through Coherent Multidimensional Spectroscopy

Dark excitons are of fundamental importance in a broad range of contexts but are difficult to study using conventional optical spectroscopy due to their weak interaction with light. We show how coherent multidimensional spectroscopy can reveal and characterize dark states. Using this approach, we identify parity-forbidden and spatially indirect excitons in InGaAs/GaAs quantum wells and determine details regarding lifetimes, homogeneous and inhomogeneous linewidths, broadening mechanisms, and coupling strengths. The observations of coherent coupling between these states and bright excitons hint at a role for a multistep process by which excitons in the barrier can relax into the quantum wells.