Fungicide selection and timing to manage southern rust of corn

Foliar corn diseases are among the most important yield-limiting factors that affect commercial corn production in the Mid-South. Southern rust is caused by the fungus Puccinia polysora, which only infects corn and is reintroduced each year from the tropic regions of Central America and the Caribbean. Symptoms consist of small orange pustules that are often first detected on leaves located in the mid- to upper-canopy. As conditions favor disease development initial infections produce spores that are spread to nearby plants and nearby fields resulting in secondary infections and the spread of southern rust

Effect of temperature and genetic structure on adaptive evolution at a dynamic range edge in the North American gypsy moth (Lymantria dispar L.)

The study of biological invasions is not only essential to regulate their vast potential for ecological and economical harm, they offer a unique opportunity to study adaptive evolution in the context of recent range expansions into novel environments. The North American invasion of the gypsy moth, Lymantria dispar L., since its introduction in 1869 to Massachusetts, has expanded westward to Minnesota, northward to Canada, and southward to North Carolina. Fluctuating range dynamics at the southern invasive edge are heavily influenced by heat exposure over their optimal (supraoptimal) during the larval stage of development. We coupled genomic sequencing with reciprocal transplant and laboratory-rearing experiments to examine the interactions of phenotypic, genetic, and environmental variation under selective supraoptimal regimes. We demonstrate that while there is no evidence to support local adaptation in the fitness-related physiological traits we measured, there are clear genomic patterns of adaptation due to differential survival in higher temperatures. Mapping of loci identified as contributing to local adaptation in a selective environment and those associated with phenotypic variation highlighted that variation in larval development time is partly driven by pleiotropic loci also affecting survival. Overall, I highlight the necessity and inferential power gained through replicating environmental conditions using both phenotypic and genome-wide analyses

Arkansas Corn and Grain Sorghum Research Studies 2024

The 2024 edition of the Arkansas Corn and Grain Sorghum Research Studies Series includes research results on topics pertaining to corn and grain sorghum production, including weed, disease, nematode, and insect management; economics; irrigation; agronomics; soil fertility; drone use; and research verification program results. Our objective is to capture and broadly distribute the results of research projects funded by the Arkansas Corn and Grain Sorghum Board. The intended audience includes producers and their advisors, current investigators, and future researchers. The Series serves as a citable archive of research results. The reports inform and guide our long-term recommendations, but should not be taken solely as our recommended practices. Some reports may appear in other University of Arkansas System Division of Agriculture’s Arkansas Agricultural Experiment Station publications. This duplication results from the overlap between disciplines and our effort to broadly inform Arkansas corn and grain sorghum producers of the research conducted with funds from the Corn and Grain Sorghum Check-off Program. This publication may also incorporate research partially funded by industry, federal, and state agencies. The use of products and trade names in any of the research reports does not constitute a guarantee or warranty of the products named and does not signify that these products are endorsed or approved to the exclusion of comparable products. All authors are either current or former faculty, staff, or students of the University of Arkansas System Division of Agriculture or scientists with the United States Department of Agriculture, Agricultural Research Service. We extend thanks to the staff at the state and county extension offices and the research centers and stations, producers and cooperators, and industry personnel who assisted with the planning and execution of the programs

Arkansas Corn and Grain Sorghum Research Studies 2023

e 2023 edition of the Arkansas Corn and Grain Sorghum Research Studies Series includes research results on topics pertaining to corn and grain sorghum production, including weed, disease, and insect management; economics; irrigation; agronomics; soil fertility; mycotoxins; cover crop management; and research verification program results. Our objective is to capture and broadly distribute the results of research projects funded by the Arkansas Corn and Grain Sorghum Board. The intended audience includes producers and their advisors, current investigators, and future researchers. The Series serves as a citable archive of research results

Arkansas Corn and Grain Sorghum Research Studies 2023

e 2023 edition of the Arkansas Corn and Grain Sorghum Research Studies Series includes research results on topics pertaining to corn and grain sorghum production, including weed, disease, and insect management; economics; irrigation; agronomics; soil fertility; mycotoxins; cover crop management; and research verification program results. Our objective is to capture and broadly distribute the results of research projects funded by the Arkansas Corn and Grain Sorghum Board. The intended audience includes producers and their advisors, current investigators, and future researchers. The Series serves as a citable archive of research results

Investigations of phase transitions in magnetic materials by magnetic-field- and temperature-dependent x-ray diffraction

The subject of this doctoral work is the assembly of a laboratory-based x-ray diffractometer with magnet and non-ambient sample temperature environment for investigations of magnetic materials. A special focus is on the versatility and accessibility of the instrument. The x-ray diffractometer serves as important analysis tool for the determination of the crystallographic unit cell and derived parameters like strain or expansion as function of the temperature and magnetic field. Some materials undergo structural or magnetic phase transformations under specific conditions, which can be induced within the x-ray diffractometer. These phase transformations, and their effect on crystallographic parameters of the investigated materials can be followed in situ in the instrument. Several case studies of investigations of magnetoelastic and magnetostructural phase transitions at temperatures between 25 to 600 K under various magnetic fields highlight the performance and capabilities of the instrument. The final x-ray diffractometer setup is equipped with a 5.5 T magnet and cryofurnace for non-ambient measurements in the range between 11–700 K. Measurements in transmission geometry result in reliable reflection intensities that allow for the refinement of structural parameters, and even structure solution from the diffraction data. The fast position-sensitive Si strip detector has a large angular coverage, and allows for quick data collections. High resolution data can be collected with the use of a monochromator crystal at the expense of photon flux instead of the high flux x-ray mirror optics. Integration of all diffractometer components into the control software enables the use of macros for automated data collection for a series of different measurement conditions. The first set of case studies is related to materials with a magnetoelastic phase transition, MnB, FeB and LaFe11.4Si1.6, which exhibit no structural change over the course of the magnetic ordering, but a large elastic response. Synchrotron and neutron scattering studies complement the characterization with the lab-based diffractometer with magnet, and reveal the first-order character of the phase transition. Spin fluctuations are the connecting driving force behind the magnetovolume effects and anomalies over the course of the phase transition in MnB, FeB and LaFe11.4Si1.6. The term spin fluctuations, however, describes different phenomena in the investigated materials and is clarified accordingly. The second set of case studies is related to the (La,Ce)Fe12B6 class of materials. They undergo a magnetic-field-induced phase transition at low temperatures that is coupled with a huge magnetostriction. The origin behind this anisotropic expansion over the course of the phase transition is determined as magnetic-field-induced magnetostructural phase transition into a new ferromagnetic structure. The structure is determined from the x-ray diffraction data collected in magnetic fields. A model for the transformation mechanism in the form of a martensitic-like phase transition is proposed. The model also explains the burst-like growth of ferromagnetic phase in the matrix of surrounding grain boundaries. A kinetic arrest of the ferromagnetic structure occurs, and results in a delay and large hysteresis of the magnetostructural phase transition

Efficacy of abamectin as a seed treatment for control of Meloidogyne incognita and Rotylenchulus reniformis on cotton

Abamectin is a blend of B1a and B1b avermectins that is being used as a seed treatment to control plant-parasitic nematodes on cotton. Data on the toxicity of abamectin and its effectiveness as a seed treatment to control Meloidogyne incognita or Rotylenchulus reniformis on cotton are lacking. The toxicity of abamectin was based on an assay of nematode mobility, LD50 values of 1.56 µg/ml and 32.9 µg/ml were calculated based on 2 hr exposure for M. incognita and R. reniformis, respectively. There was no recovery of either nematode after exposure for 1 hr to its LD50 concentration. Sublethal concentrations greater than 0.39 µg/ml for M. incognita and 8.2 µg/ml for R. reniformis reduced (P = 0.05) infectivity on tomato. In field trials, suppression (P = 0.05) of M. incognita was observed 32 DAP by abamectin seed treatment whereas no suppression of R. reniformis was observed. No suppression of M. incognita was perceived by abamectin seed treatment in microplots. Suppression of M. incognita was observed in microplots by harpinEA and harpingαβ as a seed treatment and foliar spray, respectively. Seed cotton yields were variable for abamectin-treated seed, but numerically positive for harpin-treated cotton. Initial gall formation on developing taproots was suppressed (P = 0.001), and penetration of 5-cm long taproots by M. incognita and R. reniformis was numerically suppressed by abamectin-treated compared to non-treated seed, but infection increased with root development. Using an assay of nematode mobility, the proportion of dead second-stage juveniles (J2) was higher (P = 0.05) following exposure to an excised radicle from abamectin-treated seed than non-treated seed, but lower (P = 0.05) than J2 exposed to the abamectin-treated seed coat. Thus a higher concentration of abamectin remained on the seed coat than emerging radicle. The concentration of abamectin transferred from the seed coat to the developing roots was limited, which contributed to the variability in suppression of plant-parasitic nematodes on cotton