Doctor of Philosophy / Department of Grain Science / Bhadriraju Subramanyam / Mark E. Casada / In commercial grain elevators and feed mills, the boot and pit areas contribute to commingling of insects with grain that moves through the elevator leg. A pilot-scale bucket elevator leg with a modified removable boot, or slip-boot, was used to measure the magnitude of commingling as a function of stored-product insect density and boot holding time in tests with wheat and corn. Pilot-scale tests showed that clean grain transferred over infested boots was infested with about 1 insect/kg when transferred immediately after the boot was infested; this increased to 2 insects/kg after incubating the boot for 8 wk. Larger numbers of kernels with internal infestations were picked up by clean grain during transfer compared with externally infesting insects, because the mobility of the latter enabled them to move away from buckets during transfer. Monthly surveys over two years at elevators and feed mills revealed several stored-product insects in grain residues from the boot and pit areas and bulk load-out samples. Insect densities in the boot and pit areas were impacted by seasonal temperatures and facility sanitation practices. Recommended sanitation guidelines for the boot and pit areas include: (1) boot residual grain clean-out every 30 d, (2) removal of grain spillage and floor sweepings from the pit area, and (3) proper disposal of boot and pit residual grain. Facilities following these sanitation guidelines could avoid costly grain discounts, increase income of the business operation and minimize or prevent cross contamination of clean grain by infested grain in the boot and pit areas.

During storage of grain, there may have significant damage to its quality due to unfavorable physical and biological interactions and thus requires continuous monitoring. Therefore, an easy, cost-effective and environmentally friendly method is necessary for efficient monitoring of stored-grain. Arrays of sensors are being used for classifying liquors, perfumes, quality of food products mimicking mammalian olfactory systems. Monitoring of stored grain is a new application of sensor arrays. The main objective was to fabricate a carbon black polymer sensor array which can easily monitor incipient grain spoilage by detecting spoiling stored grain volatiles (benzene derivatives and aliphatic hydrocarbon derivatives) with minimum interference from relative humidity. Various aspects of a good sensor were analyzed using statistical analysis (RSD, LDA, PCA, t-test). The developed sensor array can identify red flour beetle-infected and uninfected wheat and fungal volatiles at ambient conditions as well as some stored grain conditions (MC 16%, RH 52%).

Doctor of Philosophy / Department of Physics / Thomas W. Phillips / The emergence of heritable high-level resistance to the fumigant gas phosphine in stored-product insects is of grave concern to many grain growing countries around the world. The research reported in this dissertation was designed to determine the presence of phosphine resistance in 34 field collected populations of Rhyzopertha dominica (F.) from the United States and Canada, the potential to control resistant R. dominica populations utilizing high dose and longer exposure time strategies, and to develop a rapid assay for phosphine resistance detection. Using a discriminatory dose assay called the FAO number 16 method, adult R. dominica were sampled and subjected to a phosphine dose of 20 ppm for a fumigation exposure period of 20 h to distinguish a susceptible R. dominica adult by death from a resistant beetle that survives the treatment. Results from the study showed that 32 out of the 34 geographic populations surveyed had beetles resistant to phosphine, and the frequency of resistance varied from 97% in a population from Parlier, California to 0% in beetles from both Carnduff, Saskatchewan and Starbuck, Manitoba. A 20-hour dose response assay was used to characterize the level of resistance by calculating the resistance ratio factors using beetles from a laboratory susceptible strain and those from five of the populations sampled. This resistance ratio (RR) was based on the ratio of LC50 (estimate for the concentration to kill 50% of a test group) in the sampled population to the LC50 for the susceptible strain. The highest RR for the five resistant populations was nearly 596-fold in beetles from Belle Glade, Florida, which represented the “strong” resistance phenotype, whereas the lowest RR in that group was 9-fold in Wamego, Kansas, representing the “weak” resistance phenotype. Manipulation of concentration and exposure periods can be utilized to manage strongly resistant R. dominica populations. The effect of several phosphine concentrations and fumigation exposure periods were assessed on progeny of mixed life stage colonies of the strongly resistant R. dominica. A 48 hours dose response assay was carried out on these two strongly resistant populations to re-characterize their levels of resistance. Results from this assay showed that a phosphine dose of 730-870 ppm could control all resistant adult R. dominica. Additionally, phosphine concentrations ranging from 400-800 ppm phosphine for 96 hours completely killed mixed life stage colonies of strongly resistant lesser grain borers from the two populations studied. Lastly, fumigations done beyond 4 days at phosphine concentrations between 450-700 ppm controlled all phosphine resistant populations of lesser grain identified from our previous work. Phosphine applied at high concentrations is known to elicit a knockdown effect that can vary between susceptible and resistance grain insects. Using 18 of the 34 R. dominica populations this study sought to determine among three knockdown time (KT) techniques which method had potential to be utilized in an effective rapid assay for phosphine resistance in R. dominica. Adult R. dominica were exposed to a high concentration of phosphine (3000 ppm) to assess the time to knockdown 50%, 100% of a group of ten insects and that of single insects from the 18 geographically distinct populations vis a vis the resistance frequencies using the FAO method. KT100 quick test was better than the KT50 and Ktsingle, because bioassays were able to clearly distinguish among susceptible, weak and strong resistant individuals. Time for KT100 from susceptible populations did not exceed 30 minutes, while resistant populations had KT100 times above 30 min, with strong-resistant populations times longer than 100 min.

Doctor of Philosophy / Department of Grain Science and Industry / Subramanyam Bhadriraju / Filter cake and Triplex are powdered by-products of aluminum sulfate and soap factories, respectively. Studies were designed to determine elemental composition of these two powders and evaluate the efficacy against stored product insect species on concrete surfaces and commodities. Elemental composition of the powders was determined using conjugated scanning electron microscopy and Energy-dispersive X-ray spectroscopy. No heavy metals were found in both powders, and the dominant elements found were silicon and oxygen in the form of silicon dioxide. The efficacy of filter cake and Triplex against the maize weevil, Sitophilus zeamais Motschulsky; rice weevil, Sitophilus oryzae (Linnaeus); lesser grain borer, Rhyzopertha dominica Fabricius; red flour beetle, Tribolium castaneum (Herbst); saw-toothed grain beetle, Oryzaephilus surinamensis (Linnaeus); and Indian meal moth, Plodia interpunctella (Hübner), was determined using a range of concentrations and exposure times. On concrete surfaces ≥ 7.5 g/m² of filter cake produced more than 99% mortality of S. zeamais and S. oryzae adults within 12–24 h, whereas more than three times the concentration of filter cake was required to achieve similar mortality of both species in Triplex treatments. At 3 g/m² of filter cake, 99% mortality S. zeamais and S. oryzae adults was achieved within 22–27 h of exposure. The corresponding exposure time at 9 g/m² of Triplex was 39 h to achieve 99% mortality of both species. For both powders, lower concentrations and exposure times were required to achieve complete suppression of progeny production, percentage of insect damaged kernels, and percentage of grain weight loss compared to the concentrations and exposure times required for 00% mortality. Filter cake treated wheat at concentrations above 0.7 g/kg produced more than 99% mortality of S. zeamais and S. oryzae adults. Similarly, filter cake concentrations above 2 g/kg on wheat produced more than 99% mortality of R. dominica, T. castaneum, and O. surinamensis adults. However, on maize ≥ 3 g/kg of filter cake concentration was required to achieve similar mortality of R. dominica, T. castaneum, and O. surinamensis. Higher concentrations of Triplex were required to achieve similar mortalities of tested species on maize and wheat. Reduction in progeny production was greater when adults were exposed to higher concentrations than lower concentrations. Complete suppression of live larvae and adult emergence of P. interpunctella was achieved after exposure of eggs for 21 and 42 d to ≥ 2 g/kg of filter cake treated maize and to ≥ 0.5 g/kg of filter cake treated wheat. Similarly, complete suppression of live larvae and adult emergence was achieved when eggs were exposed to ≥ 6 g/kg of Triplex treated maize and to 3g/kg of Triplex treated wheat. In general, our study consistently showed that filter cake was more efficacious compared to Triplex against all tested species on both surfaces and commodities. Filter cake and Triplex should be recommended for protecting grain stored by smallholder farmers in Ethiopia to discourage farmers from using dangerous chemical insecticides. However, field studies should be done using both powders against stored product insects in smallholder farmers’ traditional storages structures in Ethiopia to determine concentrations that are practical under field conditions. The effective duration of protection offered by these powders should also be investigated.

Master of Science / Department of Grain Science and Industry / Bhadriraju Subramanyam / A synthetic zeolite (Odor-Z-Way, sodium aluminum silicate) used for odor adsorption was tested for its ability to control adults of stored-grain insects on wheat and on concrete petri dishes used to simulate floors of empty bins. Insect species tested included unsexed adults of the lesser grain borer, Rhyzopertha dominica (F.); rice weevil, Sitophilus oryzae (L.); maize weevil, Sitophilus zeamais (Motschuslky); red flour beetle, Tribolium castaneum (Herbst), and sawtoothed grain beetle, Oryzaephilus surinamensis (L.). Two formulations were evaluated under laboratory conditions (28±1⁰C and 65±1% r.h.): coarse zeolite (with 90% of particles having a mean diameter at or below 155 µm) and fine zeolite (with 90% of particles having a mean diameter at or below 47.0 µm). On concrete, arenas in 9-cm diameter Petri dishes were sprinkled with the synthetic zeolite to provide deposits of 0 (control), 5 and 10 g/m[superscript]2. Mortality was assessed at times ranging from 10 minutes to 24 hours followed by 48 hours recovery on wheat. Mortality in adults of the five species increased as the rate of application and the duration of exposure increased. Concrete Petri dishes sprinkled with the fine zeolite yielded percent mortality greater or equal to that observed with the coarse zeolite- sprinkled Petri dishes. Bioassays on wheat were conducted using two dosage rates: 0.1 to 3.0 g/kg for R. dominica and 0.05 to 1.0 g/kg for the other insect species. Mortality was assessed 7 days post- infestation. A concentration of 0.75 g/kg of fine or coarse zeolite achieved 100% mortality in adults of S. zeamais, T. castaneum, and O. surinamensis. All adults of S. oryzae were killed using 0.50 g/kg of coarse or fine zeolite. Adults of R. dominica were the least susceptible: 2.50 g/kg of fine zeolite and 3.0 g/kg of coarse zeolite were required for 100% mortality. Mortality generally increased with the concentration of zeolite applied on wheat. Efficacy was not related to particle size. This is the first study showing the efficacy of a synthetic zeolite against adults of five species of stored-product insects on concrete and wheat. Synthetic zeolites can be a suitable alternative to currently used pesticides for treatment of empty bin floors and stored wheat for insect control.

Master of Science / Department of Grain Science and Industry / Bhadriraju Subramanyam / The insecticides, β-cyfluthrin and chlorpyrifos-methyl plus deltamethrin, are approved in the United States for treating empty bin surfaces. Chlorpyrifos-methyl plus deltamethrin and spinosad insecticides are approved for direct treatment of wheat. The efficacy of commercial formulations of β-cyfluthrin and chlorpyrifos-methyl plus deltamethrin at labeled rates was evaluated against adults of 16 field strains of the red flour beetle, Tribolium castaneum (Herbst); seven strains of sawtoothed grain beetle, Oryzaephilus surinamensis (L.); and two strains of the lesser grain borer, Rhyzopertha dominica (F.). Concrete arenas in plastic Petri dishes (9 cm diameter) were used to simulate the concrete floor of empty bins. The time for ~100% knockdown and mortality of adults of laboratory strains of the three species was first established by exposing them to insecticide-treated concrete surfaces for 1 to 24 h. Adults of field strains of each species were exposed to specific established insecticide-time combinations. Mortality of all species was lower than knockdown, suggesting recovery after seven days when placed on food. Chlorpyrifos-methyl plus deltamethrin did not control all R. dominica and most O. ]surinamensis field strains. β-cyfluthrin was extremely effective against R. dominica but ineffective against T. castaneum and O. surinamensis field strains, even at four times the high labeled rate. Field strains of R. dominica were highly susceptible to spinosad and chlorpyrifos-methyl plus deltamethrin at labeled rates on hard red winter wheat. Strains of T. castaneum and O. surinamensis were susceptible only to the latter insecticide. Dose-response tests with spinosad on the two least susceptible field strains of each species showed the lethal dose for 99% mortality (LD[subscript]99) for T. castaneum and R. dominica field strains were similar to that of the corresponding laboratory strains. Corresponding values for the two O. surinamensis field strains were significantly greater (~6 times) than the laboratory strain. The effective dose for progeny reduction (ED[subscript]99) of only one R. dominica field strain was significantly greater (~2 times) than that of the laboratory strain. The baseline susceptibility data of field strains of three insect species to spinosad will be useful for monitoring resistance development once this product is commercially released as a grain protectant.

Storage of large amounts of grain post-harvest is common during drying, distribution and preservation of crops. During storage, where grain is usually held in a large metallic container or bin, changes in temperature, moisture, and insect infestation can cause grain to spoil annual post-harvest crop losses are estimated up to 30% in some countries while Canadian losses of 2% exceed a billion dollars. Currently, locally-sensitive temperature and moisture sensors are a common way to monitor grain bins. Sensors are generally strung on heavy duty cables that can withstand the forces generated when unloading grain. This monitoring method provides a coarse sampling of the storage environment due to system cost and the fact that using many sensor cables would require significantly reinforcing the bin. Further, these cables are not suitable for monitoring stored crops that are dried by a combination of stirring and aeration. Over the past four years, I have developed multiple electromagnetic imaging based grain-monitoring systems with the goals of overcoming the deficiencies of existing sensor technology and allowing farmers and distributors a robust way to preserve our food stores and increase revenue. The proposed technology aims to produce global, quantitative images of grain properties throughout the bin from measurements taken by a few side-mounted antennas used to interrogate the bin contents. To develop this technology intensive research was put into the design of low profile, robust antennas as well as numerical analysis of the effects of different field distributions within conducting boundaries. Both electric and magnetic field sensitive antennas were built and tested in small lab-scale as well as full-scale grain bins to experimentally evaluate the performance of such imaging system. This thesis provides details on different system designs and analysis and describes the advantages and challenges associated with the techniques described. / October 2016

Master of Science / Department of Entomology / Thomas W. Phillips / Resistance of stored-grain insects to the fumigant gas phosphine is becoming common, due to genetic-based resistance. Using proper resistance management, phosphine can continue to be effective with efficient monitoring methods. This thesis focuses on assessing the levels of phosphine resistance across North America in a common stored-product pest, the red flour beetle, Tribolium castaneum (Herbst), and on refining a rapid bioassay method so that resistance can be easily and accurately detected. Previous work found that phosphine resistance was present in two regions of the USA, the Southeast and Midwest. In this study a discriminating-dose bioassay was used with adult beetles to determine the number of resistant and susceptible individuals in a test population. Adult T. castaneum from 25 locations across the United States and Canada were collected, and 25-60 adults from each population were assessed for the percentage of resistant individuals. Thirteen populations were deemed susceptible with no resistant insects in the samples, while eight populations had 52% or fewer individuals scored as resistant, and four populations had between 88 and 100% resistant individuals. Dose-mortality experiments were conducted to characterize the “strength” of resistance. One population with 41% resistant beetles in the discriminating dose assay was 4.5-fold resistant relative to the susceptible laboratory strain, compared to 127-fold resistant for a population with all 100% scored as resistant. Adult beetles from twelve populations were used to determine if a “knockdown” test of insects exposed to a high concentration of phosphine (3000 ppm) could assess resistance as well as the discriminating-dose mortality assay. The time required for five out of ten beetles to be knocked down, called the KT[subscript]50 for the time to knockdown 50% of the sample, was useful to characterize resistance. Phosphine susceptible beetles had KT[subscript]50 values less than 15 minutes, while samples from resistant populations had KT[subscript]50’s between 15 and 52 minutes. The refined quick test and knowledge of current levels of phosphine resistance in the United States and Canada reported in this thesis point to the importance of such information in developing phosphine resistance management programs for grain insects.

Brazil has been experiencing high rates of population growth and increased demand for food, but their production presents losses both quantitative and qualitative, especially the attack of pests during storage. Acanthoscelides obtectus is one of the main pests in stored beans, its control is basically done with chemical pesticides that can leave toxic residues in the grains. For this reason they are sought alternative products such as essential oils. They are a good option for this control, since it does not leave residues in food and are obtained relatively easily by farmers form. Thus, the aim of this study was to identify lead compounds and evaluate the effect of the essential oils of six species of Eucalyptus (Eucalyptus benthamii, Eucalyptus camaldulensis, Eucalyptus dunnii, Eucalyptus saligna, Eucalyptus viminalis and Eucalyptus grandis) in control of Acanthoscelides obtectus in beans. The insecticide effect for different doses and exposure times, the repellent effect and the time of persistence of the insecticide effect was evaluated. For this purpose insecticide could be observed, based on lethal dose, and the Eucalyptus saligna showed greater efficiency in mortality compared with other species. For the repellent effect it was observed that all species tested showed repellent effect on Acanthoscelides obtectus and the persistence effect the result obtained was that the insecticidal effect of the essential oils is high during the initial period losing its effect quickly. / O Brasil vem apresentando altas taxas de crescimento populacional e aumento na demanda de alimentos, porém sua produção esta sujeita a perdas tanto quantitativas como qualitativas, principalmente pelo ataque de pragas durante o armazenamento. Acanthoscelides obtectus é uma das principais pragas em grãos de feijão armazenados, seu controle é feito basicamente com inseticidas químicos que podem deixar resíduos tóxicos nos grãos. Por esta razão buscam-se produtos alternativos, como os óleos essenciais. Eles são uma boa opção para esse controle, uma vez que não deixam resíduos nos alimentos e são obtidos de forma relativamente fácil pelos agricultores. Desse modo, o objetivo deste trabalho foi identificar os principais compostos e avaliar o efeito dos óleos essenciais de seis espécies de Eucalyptus (Eucalyptus benthamii, Eucalyptus camaldulensis, Eucalyptus dunnii, Eucalyptus saligna, Eucalyptus viminalis e Eucalyptus grandis) no controle de Acanthoscelides obtectus em feijão. Foi avaliado o efeito inseticida para diferentes doses e tempos de exposição, o efeito repelente e o tempo de persistência do efeito inseticida. Para o efeito inseticida pôde-se observar, com base na dose letal, que o Eucalyptus saligna apresentou maior eficiência na mortalidade em relação as demais espécies. Para o efeito repelente foi observado que todas as espécies testadas apresentaram efeito repelente para Acanthoscelides obtectus e para o efeito persistência o resultado obtido foi de que o efeito inseticida dos óleos essenciais é alto durante o período inicial perdendo seu efeito rapidamente.

Made available in DSpace on 2015-03-26T13:30:23Z (GMT). No. of bitstreams: 1 texto completo.pdf: 819713 bytes, checksum: bc07208206271366ce40b847926f6f9c (MD5) Previous issue date: 2009-02-13 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / The maize weevil, Sitophilus zeamais Motschulsky, 1855 (Coleoptera: Curculionidae) is considered the main pest of stored maize in Brazil and its control is achieved mainly by insecticides. The massive and intensive use of these compounds may lead to selection of resistant populations and consequently compromise the control efficacy of this insect pest in Brazilian storage facilities. This work was a survey of physiological and behavioral resistance to the insecticides esfenvalerate, permethrin and the insecticide mixture esfenvalerate + fenitrothion in 27 populations of S. zeamais collected in several Brazilian counties and Paraguay, and also investigated possible costs associated with this phenomenon. The insects were subjected to concentration-mortality bioassays to determine the lethal concentrations LC50 and CL95. The populations were also subjected to two walking trials on surfaces treated and untreated with dried insecticide residues for detection of behavioral resistance. We also determined the instantaneous rate of population increase (ri), maize consumption and body mass of individuals of each population. We also determined the respiration rate, as well as amylase and lipase activity of the insects from each population as an indication of their metabolic rate. The concentrationmortality bioassays indicated resistance ratios ranging from 0.63 to 66.65x for esfenvalerate, 1.00 to 5.02x for the insecticide mixture esfenvalerate + fenitrothion from 0.79 to 69.59x for permethrin compared with the susceptible standard population (Sete Lagoas). These results indicate a decrease in pyrethroid resistance in Brazilian populations of maize weevil compared with previous studies. The behavioral characteristics of walking in treated area varied among populations and sex. There was avoidance to permethrin- and esfenvalerate- treated surfaces by females from different populations. There was no correlation between physiological and behavioral resistance, indicating that physiological resistance is independent of behavioral resistance in the populations tested. There was no significant difference in the instantaneous rate of increase (ri), body mass and respiration rate among the insects. In contrast, there were significant differences in food consumption and amylase and lipase activity among populations. Therefore, we conclude that there was no fitness cost associated with levels of resistance observed in the populations studied. / O caruncho do milho, Sitophilus zeamais Motschulsky, 1855 (Coleoptera: Curculionidae) é considerado a principal praga do milho armazenado no Brasil, sendo o seu controle realizado principalmente por inseticidas. A utilização maciça e intensa destes compostos pode levar à seleção de populações resistentes e, conseqüentemente, à diminuição da eficiência do controle deste inseto-praga em armazéns brasileiros. Neste trabalho foi realizado um levantamento da resistência fisiológica e comportamental aos inseticidas esfenvalerato, permetrina e a mistura esfenvalerato + fenitrotiona em 27 populações de S. zeamais coletadas em várias cidades brasileiras e no Paraguai, investigando também, possíveis custos adaptativos relacionados ao fenômeno. Os insetos foram submetidos a bioensaios de concentração-mortalidade com determinação das concentrações letais CL50 e CL95. As populações foram também submetidas a dois ensaios de caminhamento em superfície tratada e não-tratada com resíduo seco de inseticida para detecção de resistência comportamental. Foram também determinados a taxa instantânea de crescimento populacional (ri), o consumo de grão de milho e massa corporal dos indivíduos de cada população estudada. Determinou-se ainda a taxa respiratória, a atividade de amilase e de lipase como indicativo da taxa metabólica dos insetos. Os resultados dos bioensaios de mortalidade indicaram variação da razão de resistência de 0,63 a 66,65 vezes para esfenvalerato, de 1,00 a 5,02 vezes para a mistura esfenvalerato + fenitrotiona e de 0,79 a 69,59 vezes para permetrina em relação à população padrão de suscetibilidade (Sete Lagoas). Estes resultados indicam uma diminuição da resistência a piretróides em populações brasileiras de caruncho do milho em relação a estudos anteriores. As características comportamentais de caminhamento na área tratada variaram entre as populações e sexo. Houve repelência de fêmeas para permetrina e esfenvalerato quando comparado entre as populações. Não foi detectada correlação entre a resistência fisiológica e a resistência comportamental, evidenciando que a resistência fisiológica é independente da resistência comportamental nas populações testadas. Não se detectou diferença significativa na taxa instantânea de crescimento (ri), na massa corpórea e na taxa respiratória dos insetos. Detectou-se diferenças no consumo alimentar e na atividade de amilase e atividade de lipase entre as populações testadas. Assim, podemos concluir que não houve custo adaptativo associado aos níveis de resistência verificados nas populações estudadas.