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Hoffmann M.,University of California at Davis | Barbella A.,Driscolls Strawberry Associates Inc. | Miller T.,University of California at Davis | Broome J.,Driscolls Strawberry Associates Inc. | And 7 more authors.
Acta Horticulturae | Year: 2017

Here we report on results of weed and pathogen control with steam over a period of four seasons (2011/12 to 2014/15). Furthermore we discuss effects of steam on plant performance, fruit yields and soil microbial community. Steam was applied by a proto-type tractor towed steam machine equipped with a Clayton steam generator. We discuss the efficacy of steam compared to fumigants and non-chemical soil disinfestation methods in California. Steam controls weeds, soil borne pests, while strawberry yields in steam treated soil normally are 20% higher, compared to common non-chemical pre-plant soil disinfestation treatments in CA. Our results suggest that the benefits of steam are due to combined effects of extra nutrient release, reduction of pathogen pressure and changes in microbial community structure. We are currently separating those effects in controlled experiments. Furthermore we investigate steam-induced changes in soil microbial community and the utilization of steam in combination with allyl isothiocyanate (AITC) and cover crops as management tool. A commercial broadcast field steam applicator is being developed in cooperation with industry.

Nansen C.,University of California at Davis | Elliott N.,USDAARS
Annual Review of Entomology | Year: 2016

Remote sensing describes the characterization of the status of objects andor the classification of their identity based on a combination of spectral features extracted from reflectance or transmission profiles of radiometric energy. Remote sensing can be benchtop based, and therefore acquired at a high spatial resolution, or airborne at lower spatial resolution to cover large areas. Despite important challenges, airborne remote sensing technologies will undoubtedly be of major importance in optimized management of agricultural systems in the twenty-first century. Benchtop remote sensing applications are becoming important in insect systematics and in phenomics studies of insect behavior and physiology. This review highlights how remote sensing influences entomological research by enabling scientists to nondestructively monitor how individual insects respond to treatments and ambient conditions. Furthermore, novel remote sensing technologies are creating intriguing interdisciplinary bridges between entomology and disciplines such as informatics and electrical engineering. © Copyright 2016 by Annual Reviews. All rights reserved.

Cole C.B.,Syngenta | Bowman D.T.,North Carolina Foundation Seed Producers Inc | Bourland F.M.,University of Arkansas | Caldwell W.D.,Louisiana State University | And 3 more authors.
Journal of Cotton Science | Year: 2016

An 18-environment field study was undertaken to observe the mean and coefficient of variation (as a measure of stability) for cotton (Gossypium hirsutum L.) lint yield components in population types that differed for lint yield stability to determine which yield components contributed to yield stability. Hybrids and blends of hybrids (heterozygous populations) were more stable than the parents and blends of parents (homozygous populations) for lint yield. No within-boll yield component showed convincing evidence of differences between population types with respect to stability. Stability observed for bolls/hectare followed the same trend as lint yield in which the heterozygous populations were more stable than homozygous populations. Heterosis for boll production was not consistent across locations and declined with increasing environmental mean. Ultimately, the difference between population types, with respect to yield and stability, was attributed to the heterozygous entries producing more bolls in the low-yielding environments while producing numbers that were similar to the homozygous populations in the high-yielding environments. This reduced the range of lint yield, reduced the variation across locations, and resulted in increased lint yield stability. Manipulating within-boll components might not increase lint yield stability. © The Cotton Foundation 2016.

Eugene B.,University of Arkansas | Moore P.A.,U.S. Department of Agriculture | Li H.,University of Delaware | Miles D.,USDAARS | And 3 more authors.
Journal of Environmental Quality | Year: 2015

Alum [Al2(SO4)3·14H2O] addition to poultry litter has been shown to reduce ammonia (NH3) concentrations in poultry houses; however, its effects on greenhouse gas (GHG; N2O, CH4, and CO2) emissions is unknown. The objectives of this study were to determine the effects of alum additions on (i) in-house NH3 and GHG concentrations, (ii) NH3 and GHG emissions, and (iii) litter chemical properties. Two identical broiler houses located in northwest Arkansas were used for this study: one house was a control and the other was treated with alum between each flock of birds. Ventilation rates were coupled with in-house NH3 and GHG measurements to determine emission rates. Overall, alum additions significantly reduced the daily average in-house NH3 concentration by 42% (8.9 vs. 15.4 μL L-1), and the overall NH3 emission rate was reduced by 47% (7.2 vs. 13.4 kg d-1 house-1). The average cumulative NH3 emission for the three flocks was 330 kg house-1 flock-1 for the alum-treated house and 617 kg house-1 flock-1 for the control. Concentrations and emissions of nitrous oxide (N2O) and methane (CH4) from the alum-treated house were not significantly different than the untreated house. However, carbon dioxide (CO2) emissions were significantly higher from the untreated house than the alum-treated house. Alum also significantly increased litter N content and reduced the C/N ratio. These results indicate that the addition of alum to poultry litter is not only an effective management practice for reducing in-house NH3 concentrations and emissions but also significantly reduces CO2 emissions from poultry facilities. © 2015 American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America.

Fortuna A.-M.,Washington State University | Honeycutt C.W.,U.S. Department of Agriculture | Vandemark G.,U.S. Department of Agriculture | Griffin T.S.,Tufts University | And 13 more authors.
Journal of Environmental Quality | Year: 2012

Soil biotic and abiotic factors strongly influence nitrogen (N) availability and increases in nitrification rates associated with the application of manure. In this study, we examine the effects of edaphic properties and a dairy (Bos taurus) slurry amendment on N availability, nitrification rates and nitrifier communities. Soils of variable texture and clay mineralogy were collected from six USDA-ARS research sites and incubated for 28 d with and without dairy slurry applied at a rate of ~300 kg N ha -1. Periodically, subsamples were removed for analyses of 2 M KCl extractable N and nitrification potential, as well as gene copy numbers of ammonia-oxidizing bacteria (AOB) and archaea (AOA). Spearman coefficients for nitrification potentials and AOB copy number were positively correlated with total soil C, total soil N, cation exchange capacity, and clay mineralogy in treatments with and without slurry application. Our data show that the quantity and type of clay minerals present in a soil affect nitrifier populations, nitrification rates, and the release of inorganic N. Nitrogen mineralization, nitrification potentials, and edaphic properties were positively correlated with AOB gene copy numbers. On average, AOA gene copy numbers were an order of magnitude lower than those of AOB across the six soils and did not increase with slurry application. Our research suggests that the two nitrifier communities overlap but have different optimum environmental conditions for growth and activity that are partly determined by the interaction of manure-derived ammonium with soil properties. © 2012 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America.

Monaco M.K.,Cold Spring Harbor Laboratory | Sen T.Z.,USDAARS | Sen T.Z.,Iowa State University | Dharmawardhana P.D.,Oregon State University | And 15 more authors.
Plant Genome | Year: 2013

A framework for understanding the synthesis and catalysis of metabolites and other biochemicals by proteins is crucial for unraveling the physiology of cells. To create such a framework for Zea mays L. subsp. mays (maize), we developed MaizeCyc, a metabolic network of enzyme catalysts, proteins, carbohydrates, lipids, amino acids, secondary plant products, and other metabolites by annotating the genes identifi ed in the maize reference genome sequenced from the B73 variety. MaizeCyc version 2.0.2 is a collection of 391 maize pathways involving 8889 enzyme mapped to 2110 reactions and 1468 metabolites. We used MaizeCyc to describe the development and function of maize organs including leaf, root, anther, embryo, and endosperm by exploring the recently published microarray-based maize gene expression atlas. We found that 1062 differentially expressed metabolic genes mapped to 524 unique enzymatic reactions associated with 310 pathways. The MaizeCyc pathway database was created by running a library of evidences collected from the maize genome annotation, genebased phylogeny trees, and comparison to known genes and pathways from rice (Oryza sativa L.) and Arabidopsis thaliana (L.) Heynh. against the PathoLogic module of Pathway Tools. The network and the database that were also developed as a community resource are freely accessible online at to facilitate analysis and promote studies on metabolic genes in maize. © Crop Science Society of America.

Hallman G.J.,USDAARS | Guo K.,Texas A&M University | Guo K.,Institute of Medical Plant Development | Liu T.-X.,Texas A&M University | Liu T.-X.,Northwest University, China
Journal of Economic Entomology | Year: 2011

Agromyzid leafminers are economic and quarantine pests of a variety of vegetables, flowers, and ornamental foliage. Methyl bromide fumigation is often used as a phytosanitary treatment when quarantined agromyzids are found in shipped commodities; alternative treatments are sought. Ionizing radiation is a viable alternative that is increasing in use worldwide. A dose of 400 Gy is accepted by USDA-APHIS for all insects (except Lepidoptera pupae and adults) on all commodities. Efforts to lower this dose and make it acceptable to other countries involve determining radiotolerance of families of major quarantine pests. Agromyzidae is one such family for which no useful information on radiotolerance exists. This research sought to determine the dose required to control a major agromyzid pest, Liriomyza trifolii (Burgess) and was performed on L. trifolii collected in Weslaco, TX, reared on Phaseolus vulgaris L. and Capsicum annuum L. and irradiated in the late puparial stage. The measure of efficacy was prevention of F1 mine formation. Puparia collected from Gossypium hirsutum L. and reared on P. vulgaris were more radiotolerant than those collected and reared on C. annuum. A dose of 214 Gy may prevent F1 mine formation of L. trifolii. This research used a variation of probit analysis where the direct response of the treated individual is not measured, but the response of the F1 generation is. This type of analysis is useful in phytosanitary irradiation research where the measure of efficacy often involves a response of the F1 generation. © 2011 Entomological Society of America.

Allen B.L.,USDAARS | Lenssen A.W.,Iowa State University | Sainju U.M.,USDAARS | Caesar-Tonthat T.,USDAARS | Evans R.G.,USDAARS
Agronomy Journal | Year: 2014

Brassicaceae oilseeds can serve as potential feedstocks for renewable biofuels to offset demand for petroleum-based alternatives. However, little is known about oilseed crop yield potential and N use in semiarid, wheat (Triticum spp.)-based cropping systems that dominate the northern Great Plains (NGP). A 5-yr study was conducted in northeast Montana to investigate the yield potential of a direct seeded system of durum (T. durum Desf.) in rotation with either chemical fallow or three Brassicaceae oilseeds: camelina [Camelina sativa (L.) Crantz], crambe (Crambe abyssinica Hochst. ex R.E. Fries), and canola-quality Brassica juncea L. Overall, results from the study indicated that seed yield in the three Brassicaceae oilseeds tested in rotation with durum was related (P < 0.001; r2 = 0.68) to a nitrogen recovery index (NRI), indicating the importance of nitrogen use (NU) efficiency in dryland oilseed production, and that B. juncea generally used N more efficiently than crambe and camelina. Similarly, NRI was related (P < 0.001; r2 = 0.72) to grain yield in durum following oilseeds. Grain yield of durum following B. juncea was similar to durum following fallow and greater than durum following camelina or crambe. Durum following crambe tended to use N more inefficiently than durum following camelina, B. juncea, or fallow. Differences in yield and N use of durum and oilseeds varied among years, which underscores the need to further develop management tools to optimize durum-oilseed cropping systems in highly variable rainfall environments typical of the NGP. © 2014 by the American Society of Agronomy, 5585 Guilford Road, Madison, WI 53711. All rights reserved.

Maxwell J.J.,Monsanto Corporation | Lyerly J.H.,North Carolina State University | Srnic G.,DuPont Pioneer | Murphy J.P.,North Carolina State University | And 5 more authors.
Crop Science | Year: 2012

Powdery mildew is a major fungal disease in wheat, especially in cool maritime climates. A novel Aegilops tauschii Coss.-derived wheat powdery mildew resistance gene present in the germplasm line NC96BGTD1 was genetically characterized as a monogenic trait in field trials using F 2- and F 4-derived lines from a NC96BGTD1 × 'Saluda' cross. Simple sequence repeat (SSR) markers were used to map and tag the resistance gene present in NC96BGTD1. Two dominant SSR markers flanking the resistance gene were identified. Xgwm635 mapped 5.5 and 8.3 cM distal to the resistance gene in the F 2 and F 4 generations, respectively. Xgpw328 mapped 16.2 cM proximal to the resistance gene in the F 2 and 13.6 cM proximal to the resistance gene in the F 4 generation. These SSR markers were previously mapped to the short arm of chromosome 7D and their positions were confirmed using Chinese Spring aneuploid and deletion stocks. Significant segregation distortion was observed in the F 4 generation with markers distal to the resistance gene showing a preference for the A. tauschii alleles while markers proximal to the resistance gene showed less significant preference for Saluda alleles. Only the adult plant resistance gene Pm38 has been mapped to the short arm of chromosome 7D but to a more proximal position than the gene in NC96BGTD1. The resistance gene described herein should be temporarily designated MlNCD1. © Crop Science Society of America.

Low temperature regular phosphine fumigations under the normal oxygen level and oxygenated phosphine fumigations under superatmospheric oxygen levels were compared for efficacy against the aphid, Nasonovia ribisnigri (Mosley), and effects on postharvest quality of romaine and head lettuce. Low temperature regular phosphine fumigation was effective against the aphid. However, a 3 d treatment with high phosphine concentrations of ≥2,000 ppm was needed for complete control of the aphid. Oxygen greatly increased phosphine toxicity and significantly reduced both treatment time and phosphine concentration for control of N. ribisnigri. At 1,000 ppm phosphine, 72 h regular fumigations at 6°C did not achieve 100% mortality of the aphid. The 1,000 ppm phosphine fumigation under 60% O2 killed all aphids in 30 h. Both a 72 h regular fumigation with 2,200 ppm phosphine and a 48 h oxygenated fumigation with 1,000 ppm phosphine under 60% O2 were tested on romaine and head lettuce at 3°C. Both treatments achieved complete control of N. ribisnigri. However, the 72 h regular fumigation resulted in significantly higher percentages of lettuce with injuries and significantly lower lettuce internal quality scores than the 48 h oxygenated phosphine fumigation. Although the oxygenated phosphine fumigation also caused injuries to some treated lettuce, lettuce quality remained very good and the treatment is not expected to have a significant impact on marketability of the lettuce. This study demonstrated that oxygenated phosphine fumigation was more effective and less phytotoxic for controlling N. ribisnigri on harvested lettuce than regular phosphine fumigation and is promising for practical use. © 2012 Entomological Society of America.

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