G93-1145 Management of the Army Cutworm and Pale Western Cutworm

This NebGuide describes the life cycle of the army cutworm and pale western cutworm, and provides recommendations for management.The army cutworm, Euxoa auxiliaris, and the pale western cutworm, Agrotis orthogonia, are sporadic pests that are distributed throughout the Great Plains. The army cutworm can be found throughout Nebraska, but is more common in the western half of the state. Because of the drier environment, the pale western cutworm is found only in the western third of Nebraska. Both cutworms can feed on a vast array of crops and weeds. Their major economic impact is limited to winter wheat and alfalfa, because these are the vulnerable crops growing in the early spring when larval feeding activity occurs. However, they can also cause substantial damage to early spring row crops (sugarbeets and corn), especially in areas where winter cereal cover crops are used

G93-1145 Management of the Army Cutworm and Pale Western Cutworm

This NebGuide describes the life cycle of the army cutworm and pale western cutworm, and provides recommendations for management.The army cutworm, Euxoa auxiliaris, and the pale western cutworm, Agrotis orthogonia, are sporadic pests that are distributed throughout the Great Plains. The army cutworm can be found throughout Nebraska, but is more common in the western half of the state. Because of the drier environment, the pale western cutworm is found only in the western third of Nebraska. Both cutworms can feed on a vast array of crops and weeds. Their major economic impact is limited to winter wheat and alfalfa, because these are the vulnerable crops growing in the early spring when larval feeding activity occurs. However, they can also cause substantial damage to early spring row crops (sugarbeets and corn), especially in areas where winter cereal cover crops are used

Effect of Calcium Source, Dietary Calcium Concentration, and Gestation Phase on Various Bone Characteristics in Gestating Gilts

Sixty gravid crossbred gilts were allotted to a 2 x 3 x 2 factorial arrangement of treatments: two Ca sources (sun-cured alfalfa meal and CaC03), three dietary concentrations of Ca (50, 75, and 100% of NRC requirements), and two phases of gestation (55 and 105 d). The objectives were to determine the effect of Ca source, dietary Ca concentration, and gestation phase on bone characteristics (bone breaking strength, bone ash percentage, bone density, and bone ash density in the rib, thoracic, and coccygeal bones), to correlate bone responses to determine relative bone activity, and to determine reliability of the coccygeal bones as indicators of Ca status in the body. At 55 d, rib strength and coccygeal ash content were lower (P \u3c .01) than at 105 d of gestation. A gestation phase x Ca concentration (P \u3c .05) interaction occurred. As Ca concentration increased, thoracic strength and rib ash responded quadratically during each gestation phase, for which at 55 d a minima and at 105 d a maxima was produced at 75% of NRC. A Ca source x Ca concentration ( P \u3c .05) interaction occurred. Gilts fed alfalfa had the lowest rib bone and ash density when fed 75% of NRC for Ca, whereas gilts fed CaC03 were highest at this level of Ca compared with the other concentrations. Generally, all bones were positively correlated with respect to their response to dietary Ca concentration. Few negative correlations were observed. At this level of physiological maturity, there was no effect of Ca source and little effect of gestation phase on the bone variables measured at the dietary Ca concentrations used in this experiment. The rib and thoracic bones seem to be the most responsive to dietary Ca concentration

G91-1023 Insects That Attack Seeds and Seedlings of Field Crops

This NebGuide discusses how to identify and control eight insects that feed on planted seeds and seedlings. Planted seeds of field crops can attract several kinds of insects. In many cases, the insects do not cause enough damage to justify control procedures. However, under some conditions seed pests may be very destructive. Seed that is slow to germinate and establish is more likely to be damaged. Situations such as first-year crops following sod or pasture, ecofallow, or reduced tillage/heavy crop residue conditions have a good chance for seed/seedling damage. Consider grower experience and past pest problems when deciding about individual fields. This NebGuide describes eight insect pests which may attack seeds and seedlings of Nebraska field crops. Illustrations of insects are magnified to better show detail; an approximate level of magnification is indicated by the number in the caption

Library Design in Combinatorial Chemistry by Monte Carlo Methods

Strategies for searching the space of variables in combinatorial chemistry experiments are presented, and a random energy model of combinatorial chemistry experiments is introduced. The search strategies, derived by analogy with the computer modeling technique of Monte Carlo, effectively search the variable space even in combinatorial chemistry experiments of modest size. Efficient implementations of the library design and redesign strategies are feasible with current experimental capabilities.Comment: 5 pages, 3 figure

Melting of the Primitive Mercurian Mantle, Insights into the Origin of Its Surface Composition

Recent findings of the MESSENGER mission on Mercury have brought new evidence for its reducing nature, widespread volcanism and surface compositional heteregeneity. MESSENGER also provided major elemental ratios of its surface that can be used to infer large-scale differentiation processes and the thermal history of the planet. Mercury is known as being very reduced, with very low Fe-content and high S and alkali contents on its surface. Its bulk composition is therefore likely close to EH enstatite chondrites. In order to elucidate the origin of the chemical diversity of Mercury's surface, we determined the melting properties of EH enstatite chondrites, at pressures between 1 bar and 3 GPa and oxygen fugacity of IW-3 to IW-5, using piston-cylinder experiments, combined with a previous study on EH4 melting at 1 bar. We found that the presence of Ca-rich sulfide melts induces significant decrease of Ca-content in silicate melts at low pressure and low degree of melting (F). Also at pressures lower than 3 GPa, the SiO2-content decreases with F, while it increases at 3 GPa. This is likely due to the chemical composition of the bulk silicate which has a (Mg+Fe+Ca)/Si ratio very close to 1 and to the change from incongruent to congruent melting of enstatite. We then tested whether the various chemical compositions of Mercury's surface can result from mixing between two melting products of EH chondrites. We found that the majority of the geochemical provinces of Mercury's surface can be explained by mixing of two melts, with the exception of the High-Al plains that require an Al-rich source. Our findings indicate that Mercury's surface could have been produced by polybaric melting of a relatively primitive mantle

The Origin of Mercury's Surface Composition, an Experimental Investigation

Introduction: Results from MESSENGER spacecraft have confirmed the reduced nature of Mercury, based on its high core/mantle ratio and its FeO-poor and S-rich surface. Moreover, high resolution images revealed large volcanic plains and abundant pyroclastic deposits, suggesting major melting stages of the Mercurian mantle. In addition, MESSENGER has provided the most precise data to date on major elemental compositions of Mercury's surface. These results revealed considerable chemical heterogeneities that suggested several stages of differentiation and re-melting processes. This interpretation was challenged by our experimental previous study, which showed a similar compositional variation in the melting products of enstatite chondrites, which are a possible Mercury analogue. However, these experimental melts were obtained over a limited range of pressure (1 bar to 1 gigapascal) and were not compared to the most recent elemental maps. Therefore, here we extend the experimental dataset to higher pressures and perform a more quantitative comparison with Mercury's surface compositions measured by MESSENGER. In particular, we test whether these chemical heterogeneities result from mixing between polybaric melts. Our experiments and models show that the majority of chemical diversity of Mercury's surface can result from melting of a primitive mantle compositionally similar to enstatite chondrites in composition at various depths and degrees of melting. The high-Mg region's composition is reproduced by melting at high pressure (3 gigapascals) (Tab. 1), which is consistent with previous interpretation as being a large degraded impact basin based on its low elevation and thin average crust. While low-Mg NVP (North Volcanic Plains) are the result of melting at low pressure (1 bar), intermediate-Mg NVP, Caloris Basin and Rachmaninoff result from mixing of a high-pressure (3 gigapascals) and low-pressure components (1 bar for Rachmaninoff and 1 gigapascal for the other regions) (Tab. 1). Moreover, all compositions suggest mixing between low and high degree melts that indicate important differentiation processes

Metal-Silicate-Sulfide Partitioning of U, Th, and K: Implications for the Budget of Volatile Elements in Mercury

During formation of the solar system, the Sun produced strong solar winds, which stripped away a portion of the volatile elements from the forming planets. Hence, it was expected that planets closest to the sun, such as Mercury, are more depleted in volatile elements in comparison to other terrestrial planets. However, the MESSENGER mission detected higher than expected K/U and K/Th ratios on Mercury's surface, indicating a volatile content between that of Mars and Earth. Our experiments aim to resolve this discrepancy by experimentally determining the partition coefficients (D(sup met/sil)) of K, U, and Th between metal and silicate at varying pressure (1 to 5 GPa), temperature (1500 to 1900 C), oxygen fugacity (IW-2.5 to IW-6.5) and sulfur-content in the metal (0 to 33 wt%). Our data show that U, Th, and K become more siderophile with decreasing fO2 and increasing sulfur-content, with a stronger effect for U and Th in comparison to K. Using these results, the concentrations of U, Th, and K in the bulk planet were calculated for different scenarios, where the planet equilibrated at a fO2 between IW-4 and IW-7, assuming the existence of a FeS layer, between the core and mantle, with variable thickness. These models show that significant amounts of U and Th are partitioned into Mercury's core. The elevated superficial K/U and K/Th values are therefore only a consequence of the sequestration of U and Th into the core, not evidence of the overall volatile content of Mercury