105 research outputs found
Contrasting Influence of Natural Nighttime Illumination on Capture Rates of the American Burying Beetle and Roundneck Burying Beetle (Coleoptera: Silphidae)
No full textFig. 3. Seasonal dynamics of illumination of the moon (%) and raw trap counts for the A) Oklahoma and B) Nebraska data sets. Raw counts do not account for trap number, clouds, or other weather variables.Published as part of Wormington, Jillian D., Risser, Kyle, Hoback, W. Wyatt, Giles, Kristopher L., Greenwood, Carmen & Luttbeg, Barney, 2017, Contrasting Influence of Natural Nighttime Illumination on Capture Rates of the American Burying Beetle and Roundneck Burying Beetle (Coleoptera: Silphidae), pp. 339-347 in The Coleopterists Bulletin 71 (2) on page 346, DOI: 10.1649/0010-065X-71.2.339, http://zenodo.org/record/536395
Ecological Studies of the Psocid Liposcelis rufa Broadhead (Psocoptera: Liposcelididae)
No full textPsocids (Psocoptera) have risen to prominence as serious pests of stored-products worldwide in the last two decades. However, very little is known about their ecology and biology which is crucial for the development of effective management strategies. In this study, I investigated the effects of constant temperatures and relative humidities on the population growth, effect of constant temperatures at optimal relative humidity on the development and reproductive parameters of Liposcelis rufa in order to elucidate the influence of environmental conditions on its biology and the ecology. My research has shown that L. rufa can survive and multiply at a low relative humidity of 55% at temperatures of 22.5 to 30C and a high temperature of 40.0C at 75% RH. The optimal conditions for reproduction for this species are 35.0C and 75% RH where population increased 73- fold. The shortest developmental time from egg to adult was recorded at 37.5C; at this temperature development of female was completed in 21.6 d. Males have shorter life cycle than females and this may be due to the fact that females have one more instar compared to males. L. rufa males had two to four instars whereas females had two to five instars. Temperature has significant effect on development time for all developmental stages. Also, my work has demonstrated that L. rufa has a higher intrinsic rate of population increase compared to other psocid species (0.18). It oviposits at a wider range of temperature from 25 to 40C, and the highest fecundity was recorded at 30C (63 eggs).The highest oviposition rate was recorded at 35C (15.4 eggs/ female/ wk), 2 wk after the initiation of oviposition. L. rufa can live up to 9 wk at 40C, and the longest living individual lived 219 d at 27.5C. Given its ability to multiply rapidly at high temperatures and relative humidities, its short life cycle, high intrinsic rate of increase, and the ability to live for long, especially at higher temperatures suggests L. rufa has great potential to be a serious stored product pest in hot and humid climates. In addition, it is likely to have a broader ecological distribution because it can survive and multiply at temperatures of 22.5 - 40C and 55-75% RH. Finally, the temperature-dependent equations I have developed for L. rufa developmental stages and reproductive parameters can be used to elucidate its population dynamics and to facilitate the development of effective management strategies for this pest.Department of Entomology and Plant Patholog
Optimization of nitrogen fertilizer application enhances biocontrol function and net income
No full textThe intensive use of nitrogen fertilizer has been a common approach for pursuing higher crop yields. However, the ecological effects of such use on the tritrophic interactions (crop-insect pest-natural enemy) and on the ecological and economic benefits of such use are poorly understood. Here, we investigated the effects of low, medium, and high levels of nitrogen fertilizer inputs (70, 140, and 280 kg/ha/yr) on cereal aphid (Sitobion avenae Fabricius [Hemiptera: Aphididae], Schizaphis graminum Rondani [Hemiptera: Aphididae], and Rhopalosiphum padi L. [Hemiptera: Aphididae]) abundance, primary parasitism rates, crop yield, and net income in winter wheat (Triticum aestivum [Poales: Poaceae] cv. Zhou 22) for 2 yr. A higher input of nitrogen fertilizer significantly enhanced the abundance of cereal aphids, while their primary parasitism rates (26.9 ± 3.5% in 2018 and 24.9 ± 4.5% in 2019) were highest at the medium nitrogen level. The performance of participants in the wheat-aphids-parasitoids system was likewise mediated by the nitrogen fertilizers. Meanwhile, wheat yield significantly increased with moderate increases in the nitrogen level, although overuse of nitrogen fertilizer did not significantly further enhance wheat yield. Finally, we found either low or overuse of nitrogen fertilizers resulted in lower net income than did medium nitrogen fertilization. These results demonstrate the need to reevaluate and adjust fertilizer use to optimize the eco-economic and sustainable management of agroecosystems
Effects of Intraguild Predation of Lysiphlebus Testaceipes by Chrysoperla Rufilabris Larvae
No full textWinter wheat (Triticum aestivum L.) is a major commodity grown in the Southern Great Plains. The most common and destructive pest in winter wheat is the greenbug (Schizaphis graminum Rondani). Fortunately, the greenbug has several natural enemies including the endoparasitoid wasp Lysiphlebus testaceipes Cresson and predatory lacewing larvae. These organisms comprise a 'guild' of greenbug natural enemies. When one guild members consumes another guild member it is termed intraguild predation. The studies conducted in this thesis examine how Chrysoperla rufilabris Burmeister biology is affected when involved in intraguild predation interactions with L. testaceipes. Studies involved documenting intraguild predation effects on lacewing larval feeding capability and handling time, as well as larval development, survival and adult body weight. First and third instar C. rufilabris were capable of attacking and consuming mummified greenbugs during 30min feeding observations. Handling times for first instars differed significantly for larvae supplied mummies versus greenbugs; however, there were no differences among the feeding parameters for third instars. Lacewing larvae were reared on 2mg/day diets: unparasitized greenbugs, pea aphids, mummies, and mummies plus a moist cotton ball. Larvae supplied either mummy diet had lower survival for all larval instars and the pupal stage. Development was significantly shorter for larvae supplied the greenbug diet in the first instar and pupal stage. However, there were no differences in total preimaginal survival and development among the diet treatments.Department of Entomology and Plant Patholog
Influence of Warm-season Cover Crop on No-till Winter Wheat (Triticum Aestivum L.) Production
No full textDue to the adverse economic and ecological consequences of the conventional-till, monoculture winter wheat production system that dominates Oklahoma, producers are interested in no-till farming practices and diversifying their cropping systems through crop rotation and cover crops. In response to this interest, we evaluated cover crop biomass production and canopy closure, winter wheat nitrogen requirement, Hessian fly infestation pressure and final wheat grain yield response to warm-season cover crops in no-till, dual-purpose and grain-only wheat production systems. Experimental design was a split split-block with cover crop treatment (cowpea, soybean, guar, sorghum-sudangrass, pearl millet and fallow control) seeded following wheat harvest and chemically terminated approximately 45 days after seeding as whole plots. Sub plot treatment was winter wheat variety (Duster and Endurance) sown into the standing cover crop residue. Sub-sub plots were topdress nitrogen application (non-fertilized or nitrogen rate determined by sensor based nitrogen rate recommendation). During 2009 and 2010, sorghum-sudangrass, pearl millet, and cowpea provided quick biomass and canopy closure, making them well suited for weed suppression and soil erosion prevention. In both dual-purpose and grain-only production systems, wheat productivity following fallow was equal to or greater than wheat following cover crops in almost all categories. Wheat following legume cover crops, in most cases, had production levels equal to or greater than wheat following grass cover crops; however, cover crops had no effect on Hessian fly infestation. Differences in Hessian fly infestation between resistant (Duster) and susceptible (Endurance) wheat varieties were found. Grain yield was not affected by differences in Hessian fly infestation, as infestation pressure was below the economic injury threshold. The integration of cash crops may be a better solution than cover crops, as producers can achieve many of the same benefits associated with cropping system diversification as seen with cover crops as well as receive economic returns through cash crop production.Department of Plant and Soil Science
Phosphine resistance and biological control of psocids (Psocodea: Liposcelididae)
No full textPhosphine (PH₃) resistance and tolerance contribute to the increased importance of psocids (Psocodea: Liposcelididae) as stored-product pests worldwide. However, there is currently no superior substitute for this fumigant to meet domestic and international export phytosanitary requirements in the United States. These studies were conducted in the context of developing PH₃ resistance monitoring strategies to manage resistance in psocids and assessing predatory behaviors of Cheyletus eruditus (Schrank) and Cheyletus malaccensis Oudemans (Trombidiformes: Cheyletidae) to measure their potential as effective biocontrol candidates for psocid management. The first objective was to establish the levels of PH tolerance in laboratory susceptible strains of psocids using a modified FAO Method No.16. To accomplish this, discriminating doses (DDs) were established for lab-cultured susceptible adults of Liposcelis bostrychophila (Badonnel), L. entomophila (Enderlein), L. decolor (Pearman), L. paeta Pearman, L. rufa Broadhead, L. obscura Broadhead, L. fusciceps Badonnel, and Lepinotus reticulatus Enderlein (Psocodea: Liposcelididae) over a 20-h and 72-h fumigation period. The established DDs showed a range of 65.6–697.3 ppm and 18.1–194.5 ppm over 20-h and 72-h fumigation periods, respectively. The higher heterogeneity levels found in the standard 20-h fumigation period indicates the potential for a significant increase in PH₃ resistance in field populations subjected to PH₃ fumigation. The second and third objectives were to assess the predatory efficiency of C. eruditus and C. malaccensis based on their foraging behaviors —functional and numerical responses of these predators to different developmental stages of L. decolor. Both predatory mites showed Holling Type II functional response to nymphs, adult males, or adult females of L. decolor. The estimated functional response variables showed that C. eruditus performance was preferable to C. malaccensis. However, numerical response parameters of predators indicated that C. malaccensis was more efficient than C. eruditus. The fourth objective was to provide quantitative data based on the ecological interactions of C. eruditus or C. malaccensis and L. decolor under different release ratios (predator-prey ratios), temperatures (°C), and relative humidities (RH %) over a 40-d period to determine the optimal psocids management conditions for each predatory mite. The results showed that low RH (≤63%) undermine the efficacy of both predatory mites, however, C. eruditus and C. malaccensis caused psocid population suppression of ~ 67.1–97.2% and increased their progeny by ~ 117.1–1182.6% for the 1:20–10:20 release ratios, temperatures of 20–32°C, and 75–85% RH. Future research should be aimed at using the established DDs for the detection of PH₃ resistance and estimation of resistance frequencies in field-collected populations of the psocid species investigated. Also, field evaluation of both predatory mites and their compatibility with other stored-product pest management tactics are needed to permit release for psocid management in the United States
Effects of interspecific competition and narrow-spectrum insecticides on the survival and development of Diaeretiella rapae in Oklahoma winter canola
No full textDiaeretiella rapae plays a significant role in aphid suppression across its range. This parasitoid wasp specializes on crucifer-feeding aphids, now common in a rapidly expanding crop (winter canola) in the US Southern Great Plains. Diaeretiella rapae is currently found almost exclusively in winter canola during the spring when aphid intensities are high, yet does not frequently maintain aphid populations below economic thresholds. The minimal role that D. rapae plays in regulating aphids may be influenced by competing natural enemies and/or disruptive management approaches. The abundance and generalist behavior of L. testaceipes may result in frequent competitive interactions between these two parasitoids, either through extrinsic interference (if D. rapae can discriminate parasitized hosts), or intrinsic (i.e., larval) competition inside aphid hosts. Additionally, D. rapae may face significant mortality in the face of frequent applications of broad-spectrum insecticides common in winter canola. This mortality source could be minimized by the use of selective insecticides, such as flonicamid and sulfoxaflor, which have specificity to hemipteran pests and little to no effect on natural enemies. Laboratory experiments were designed to determine the outcomes of competition between D. rapae and L. testaceipes on L. pseudobrassicae and M. persicae hosts on winter canola, and on Rhopalosiphum padi hosts on winter wheat. Separate experiments were conducted in the field and laboratory to determine lethal and sub-lethal effects of flonicamid and sulfoxaflor on preimaginal D. rapae. Results indicate a reduced percentage of canola aphids are parasitized when D. rapae forages simultaneously with L. testaceipes, suggesting the proximity of canola fields to winter wheat may enhance colonization of canola by L. testaceipes and reduce the suppressive effects of D. rapae on aphids in this crop. Results from experiments with selective insecticides revealed application of flonicamid resulted in effective suppression of aphids while retaining higher rates of parasitism post-treatment when compared with other insecticides. Furthermore, the minimal sub-lethal effects of flonicamid on D. rapae suggest this insecticide is compatible with biological control. By using selective insecticides, such as flonicamid, populations of D. rapae in winter canola may be conserved and thus offset the negative effects of competition with L. testaceipes
Areawide Pest Management of Cereal Aphids in Dryland Wheat Systems of the Great Plains, USA
No full textIn the Great Plains of the USA from Wyoming to Texas, dryland winter wheat either is regularly grown continuously or is followed by a year of fallow in semi-arid locales (Royer and Krenzer, 2000). It has been well documented that these continuous monocultures can, over time, lead to increased levels of all types of pests (i.e. insects, diseases and weeds) (Andow, 1983, 1991; Vandermeer, 1989; Cook and Veseth, 1990; Elliott et al., 1998a; Way, 1998; Ahern and Brewer, 2002; Boyles et al., 2004; Brewer and Elliott, 2004; Men et al., 2004). Relative to insect pests, the ephemeral nature of insect host resources in these mono culture systems is assumed to curtail the efficiency of natural enemies, leading to increased pest pressure and reduced yields (Booij and Noorlander, 1992; Tscharntke et al., 2005; Clough et al., 2007).
From an ecological standpoint, the absence of habitats that support natural enemies in these monoculture agricultural systems are considered a primary reason why populations of aphids such as the greenbug (GB, Schizaphis graminum) and the Russian wheat aphid (RWA, Diuraphis noxia) increase above economic injury levels (EILs) (Elliott et al., 1998b, 2002a; French and Elliott, 1990a; Brewer et al., 2001; French et al., 2001a; Giles et al., 2003; Brewer and Elliott, 2004). Economic losses associated with both GB and RWA average US$150 million annually across the Great Plains of the USA (Webster, 1995; Morrison and Pears, 1998)
Circumventing ovicidal deficiencies of fumigants during postharvest fumigations
No full textSulfuryl fluoride (SF) is an increasingly used methyl bromide alternative for postharvest disinfestation of United States-produced walnuts. However, eggs of several key walnut pests are not adequately controlled by this fumigant at recommended label rate. These studies were conducted in the context of overcoming ovicidal deficiencies of SF during rapid field disinfestations. The first objective was to investigate the role of egg morphology in the context of species-specific fumigant efficacies. To accomplish this, the abundance, distribution, and location of respiratory openings on eggs of Carpophilus hemipterus (L.), Tribolium castaneum (Herbst), Lasioderma serricorne (F.), Plodia interpunctella (Hubner), Ephestia elutella (Hubner), and Amyelois transitella (Walker) were compared. Chorion structures and thicknesses of these species were also compared. Presence, distribution, and location of respiratory structures varied among species. This was the case for chorionic structures and thicknesses as well. The second objective was to establish dose responses of eggs of key walnut pests, namely, C. hemipterus, T. castaneum, L. serricorne, P. interpunctella, E. elutella, A. transitella, and Cydia pomonella (L.) to propylene oxide (PPO) in combination with 100 mmHg or carbon dioxide and normal atmospheric pressure. Results showed that PPO is an effective ovicide. Mortality tests on all insect species resulted in LC99 values ranging from 24.7-167.9 mg/liter at 100 mmHg and 4.0-17.3 mg/liter in combination with carbon dioxide. Corresponding CT (concentration x time) products were 49.3-674.4 mg h/liter and 95.3-414.8 mg h/liter, respectively. In general, coleopteran eggs were more tolerant to PPO compared to lepidopteran eggs, but L. serricorne was the exception. Findings from these studies suggest that species-specific ovicidal efficacies are possibly related to surface morphology of eggs, and that chorionic respiratory structure and chorion thicknesses may differentially affect fumigant penetration/uptake. PPO efficacy data provides information on concentrations of PPO required to kill eggs of key walnut pests at reduced and normal atmospheric pressure. These toxicity data represent a critical initial step in formulating a SF-PPO blend to meet postharvest disinfestation requirements of the California walnut industry. Future research should be aimed determining the absorbance and residue levels of propylene oxide and commercial testing of the blend
Genetic Variation Within and Between Russian wheat aphid, Diuraphis noxia (Kurdjumov), Biotypes Found in the United States
No full textThe Russian wheat aphid, Diuraphis noxia (Kurdjumov), is a pest on wheat and barley in the Western United States. Management is achieved primarily by resistant varieties. In 2003, the Russian wheat aphid caused damage to wheat with the Dn4 resistance gene in Southeastern Colorado. The damaging biotype was designated RWA-2 and the extant population RWA-1. Plant response experiments showed variation within RWA-2 clones based on chlorosis, plant height, and shoot dry weight to wheat with the Dn4 resistance gene. Phenotypic variation found within RWA-2 argues against the hypothesis that RWA-2 populations consist of a single, genetically identical clone. I conducted studies to observe variation between and within Russian wheat aphid biotypes using 12 clones of RWA-1 and RWA-2 biotype, and a single clone of: RWA-3; RWA-4; and RWA-5 biotypes, determined according to plant response to Dn genes. Using RAPD-PCR, three single band polymorphisms were detected distinguishing RWA-5 and clone 7 (RWA-2) after screening all Russian wheat aphids with 58 primers. I found no sequence variation within or between biotypes in a 436 bp fragment of the COI gene in the mtDNA. Seven microsatellite DNA markers were used to evaluate clonal diversity, but no variation was found. In addition, cuticular hydrocarbon analysis was performed on multiple aphids belonging to a single clone of RWA-1, RWA-2, RWA-3, RWA-4, and RWA-5. This method showed RWA-1 and RWA-2 had unique hydrocarbon mixtures, based on principal component analysis. Ultimately all five biotypes could be separated according to canonical variables. Using genotypic markers, Russian wheat aphid biotypes are homogenous, and consist of a single introduction into the United States. Using phenotypic markers, RWA-1 and RWA-2 are more distinctive of the five Russian wheat aphid biotypes. Lack of genotypic variation could have resulted from a founder effect upon introduction into North America, followed by bottlenecking of populations in the United States.Department of Entomology and Plant Patholog
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