Evaluating Pollination Deficits in Pumpkin Production in New York

Potential decreases in crop yield from reductions in bee-mediated pollination services threaten food production demands of a growing population. Many fruit and vegetable growers supplement their fields with bee colonies during crop bloom. The extent to which crop production requires supplementary pollination services beyond those provided by wild bees is not well documented. Pumpkin, Cucurbita pepo L., requires bee-mediated pollination for fruit development. Previous research identified the common eastern bumble bee, Bombus impatiens (Cresson), as the most efficient pumpkin pollinator. Two concomitant studies were conducted to examine pollination deficits in New York pumpkin fields from 2011 to 2013. In the first study, fruit weight, seed set, and B. impatiens visits to pumpkin flowers were compared across fields supplemented with B. impatiens colonies at a recommended stocking density of five colonies per hectare, a high density of 15 colonies per hectare, or not supplemented with bees. In the second study, fruit weight and seed set of pumpkins that received supplemental pollen through hand-pollination were compared with those that were open-pollinated by wild bees. Results indicated that supplementing pumpkin fields with B. impatiens colonies, regardless of stocking density, did not increase fruit weight, seed set, or B. impatiens visits to pumpkin flowers. Fruit weight and seed set did not differ between hand- and open-pollinated treatments. In general, we conclude that pumpkin production in central New York is not limited by inadequate pollination services provided by wild bees and that on average, supplementation with B. impatiens colonies did not improve pumpkin yiel

Long-Distance Dispersal Potential for Onion Thrips (Thysanoptera: Thripidae) and Iris yellow spot virus (Bunyaviridae: Tospovirus) in an Onion Ecosystem

Onion thrips, Thrips tabaci Lindeman, is a worldwide pest of onion whose feeding damage and transmission of Iris yellow spot virus (IYSV) may reduce onion yields. Little is known about the seasonal dynamics of T. tabaci dispersal, the distance of dispersal, or the movement of thrips infected with IYSV during the onion-growing season. To address these questions, T. tabaci adults were collected using transparent sticky card traps in commercial onion fields three times during the onion-growing season (June, July, and late August) at varying heights above the canopy (0.5-6 m above soil surface) and with trap-equipped unmanned aircraft (UAVs) flying 50-60 m above onion fields during August sampling periods in 2012 and 2013. Randomly selected subsamples of captured T. tabaci were tested for IYSV using RT-PCR. Most T. tabaci adults were captured in late August and near the onion canopy (<2 m) throughout the season. However, 4% of T. tabaci adults captured on sticky cards were at altitudes ≥2 m, and T. tabaci were also captured on UAV-mounted traps. These data strongly suggest that long-distance dispersal occurs. More T. tabaci captured on sticky cards tested positive for IYSV in August (53.6%) than earlier in the season (2.3 to 21.5% in June and July, respectively), and 20 and 15% of T. tabaci captured on UAV-mounted traps tested positive for IYSV in 2012 and 2013, respectively. Our results indicate that T. tabaci adults, including viruliferous individuals, engage in long-distance dispersal late in the season and likely contribute to the spread of IYS

Weed Hosts for Onion Thrips (Thysanoptera: Thripidae) and Their Potential Role in the Epidemiology of Iris Yellow Spot Virus in an Onion Ecosystem

Onion thrips, Thrips tabaci Lindeman, is a key foliage-feeding pest of onion worldwide and the principal vector of a serious onion pathogen, Iris yellow spot virus (IYSV). Long-term management of T. tabaci and IYSV will require an understanding of T. tabaci ecology and IYSV epidemiology in onion ecosystems. This study focused on identifying winter-annual, biennial and perennial weed species that host both T. tabaci and IYSV. Unlike summer-annual weeds, weeds with these habits survive overwinter and could serve as a green bridge for IYSV to survive between onion-growing seasons. T. tabaci larvae and adults were sampled every two weeks from 69 weed species in five areas located adjacent to onion fields in western New York in 2008 and 2009. Twenty-five of the 69 weed species were identified as hosts for T. tabaci larvae and populations were highest on the Brassicaceous weeds, Barbarea vulgaris Ait. f., Sinapis arvensis L., and Thalspi arvense L. None of these species are hosts for IYSV. Four of the 25 weed species were hosts for both T. tabaci larval populations and IYSV: common burdock, Arctium minus Bernh., dandelion, Taraxacum officinale G.H. Weber ex Wiggers, curly dock, Rumex crispus L., and chicory, Cichorium intybus L. Of these four weed species, T. officinale and A. minus may play an important role in the epidemiology of IYSV in New York onion fields because they may survive between onion-growing seasons, they are relatively abundant in the landscape, and they support relatively high densities of T. tabac

Cold spray deposition of metallic-UHTC composites

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The potential role of methanesulfonic acid (MSA) in aerosol formation and growth and the associated radiative forcings

Atmospheric marine aerosol particles impact Earth's albedo and climate. These particles can be primary or secondary and come from a variety of sources, including sea salt, dissolved organic matter, volatile organic compounds, and sulfur-containing compounds. Dimethylsulfide (DMS) marine emissions contribute greatly to the global biogenic sulfur budget, and its oxidation products can contribute to aerosol mass, specifically as sulfuric acid and methanesulfonic acid (MSA). Further, sulfuric acid is a known nucleating compound, and MSA may be able to participate in nucleation when bases are available. As DMS emissions, and thus MSA and sulfuric acid from DMS oxidation, may have changed since pre-industrial times and may change in a warming climate, it is important to characterize and constrain the climate impacts of both species. Currently, global models that simulate aerosol size distributions include contributions of sulfate and sulfuric acid from DMS oxidation, but to our knowledge, global models typically neglect the impact of MSA on size distributions. In this study, we use the GEOS-Chem-TOMAS (GC-TOMAS) global aerosol microphysics model to determine the impact on aerosol size distributions and subsequent aerosol radiative effects from including MSA in the size-resolved portion of the model. The effective equilibrium vapor pressure of MSA is currently uncertain, and we use the Extended Aerosol Inorganics Model (E-AIM) to build a parameterization for GC-TOMAS of MSA's effective volatility as a function of temperature, relative humidity, and available gas-phase bases, allowing MSA to condense as an ideally nonvolatile or semivolatile species or too volatile to condense. We also present two limiting cases for MSA's volatility, assuming that MSA is always ideally nonvolatile (irreversible condensation) or that MSA is always ideally semivolatile (quasi-equilibrium condensation but still irreversible condensation). We further present simulations in which MSA participates in binary and ternary nucleation with the same efficacy as sulfuric acid whenever MSA is treated as ideally nonvolatile. When using the volatility parameterization described above (both with and without nucleation), including MSA in the model changes the global annual averages at 900&thinsp;hPa of submicron aerosol mass by 1.2&thinsp;%, N3 (number concentration of particles greater than 3&thinsp;nm in diameter) by −3.9&thinsp;% (non-nucleating) or 112.5&thinsp;% (nucleating), N80 by 0.8&thinsp;% (non-nucleating) or 2.1&thinsp;% (nucleating), the cloud-albedo aerosol indirect effect (AIE) by −8.6&thinsp;mW&thinsp;m−2 (non-nucleating) or −26&thinsp;mW&thinsp;m−2 (nucleating), and the direct radiative effect (DRE) by −15&thinsp;mW&thinsp;m−2 (non-nucleating) or −14&thinsp;mW&thinsp;m−2 (nucleating). The sulfate and sulfuric acid from DMS oxidation produces 4–6 times more submicron mass than MSA does, leading to an ∼10 times stronger cooling effect in the DRE. But the changes in N80 are comparable between the contributions from MSA and from DMS-derived sulfate/sulfuric acid, leading to comparable changes in the cloud-albedo AIE. Model–measurement comparisons with the Heintzenberg et al. (2000) dataset over the Southern Ocean indicate that the default model has a missing source or sources of ultrafine particles: the cases in which MSA participates in nucleation (thus increasing ultrafine number) most closely match the Heintzenberg distributions, but we cannot conclude nucleation from MSA is the correct reason for improvement. Model–measurement comparisons with particle-phase MSA observed with a customized Aerodyne high-resolution time-of-flight aerosol mass spectrometer (AMS) from the ATom campaign show that cases with the MSA volatility parameterizations (both with and without nucleation) tend to fit the measurements the best (as this is the first use of MSA measurements from ATom, we provide a detailed description of these measurements and their calibration). However, no one model sensitivity case shows the best model–measurement agreement for both Heintzenberg and the ATom campaigns. As there are uncertainties in both MSA's behavior (nucleation and condensation) and the DMS emissions inventory, further studies on both fronts are needed to better constrain MSA's past, current, and future impacts upon the global aerosol size distribution and radiative forcing.</p

Aerosol pH indicator and organosulfate detectability from aerosol mass spectrometry measurements

Aerosol sulfate is a major component of submicron particulate matter (PM1). Sulfate can be present as inorganic (mainly ammonium sulfate, AS) or organosulfate (OS). Although OS is thought to be a smaller fraction of total sulfate in most cases, recent literature argues that this may not be the case in more polluted environments. Aerodyne aerosol mass spectrometers (AMSs) measure total submicron sulfate, but it has been difficult to apportion AS vs. OS as the detected ion fragments are similar. Recently, two new methods have been proposed to quantify OS separately from AS with AMS data. We use observations collected during several airborne field campaigns covering a wide range of sources and air mass ages (spanning the continental US, marine remote troposphere, and Korea) and targeted laboratory experiments to investigate the performance and validity of the proposed OS methods. Four chemical regimes are defined to categorize the factors impacting sulfate fragmentation. In polluted areas with high ammonium nitrate concentrations and in remote areas with high aerosol acidity, the decomposition and fragmentation of sulfate in the AMS is influenced by multiple complex effects, and estimation of OS does not seem possible with current methods. In regions with lower acidity (pH \u3e 0) and ammonium nitrate (fraction of total mass \u3c 0.3), the proposed OS methods might be more reliable, although application of these methods often produced nonsensical results. However, the fragmentation of ambient neutralized sulfate varies somewhat within studies, adding uncertainty, possibly due to variations in the effect of organics. Under highly acidic conditions (when calculated pH \u3c 0 and ammonium balance \u3c 0.65), sulfate fragment ratios show a clear relationship with acidity. The measured ammonium balance (and to a lesser extent, the HySO+x / SO+x AMS ratio) is a promising indicator of rapid estimation of aerosol pH \u3c 0, including when gas-phase NH3 and HNO3 are not available. These results allow an improved understanding of important intensive properties of ambient aerosols