Made available in DSpace on 2014-06-11T19:34:59Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-12-19Bitstream added on 2014-06-13T19:44:45Z : No. of bitstreams: 1 serra_me_dr_botfca.pdf: 858146 bytes, checksum: 84a2ab1f09b242594389dd1466b66b56 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / O controle químico de pragas e doenças é uma prática imprescindível no manejo fitossanitário do algodoeiro para a redução das perdas de produtividade. Com o intuito de promover o uso racional dos produtos fitossanitários nessa cultura, esse trabalho teve por objetivo comparar três tecnologias de pulverização: assistida por ar, assistida por ar associada a gotas com carga elétrica e convencional (sem ar e carga elétrica) combinadas aos volumes de 50 e 100L.ha-1, sobre a deposição e cobertura da pulverização, controle de insetos pragas e doenças e produtividade da cultura do algodão. Os experimentos foram conduzidos no delineamento de blocos ao acaso com seis tratamentos e quatro repetições para avaliação da deposição, cobertura e controle de pragas e doenças. As pulverizações foram realizadas em dois estádios de desenvolvimento das plantas conduzidas nos espaçamentos de 0,45 m e 0,90 m entre linhas de semeadura da cultura. Para isso, utilizou-se um pulverizador autopropelido equipado com pontas de pulverização de jato cônico vazio, JA-1 (50L.ha-1) e JA-2 (100L.ha-1) na pressão de 828 kPa. Foi avaliado o efeito das respectivas tecnologias no controle de Pseudoplusia includens, Bemisia tabaci, Aphis gossypii, Spodoptera spp. e Thrips spp. e da doença fúngica Ramularia areola durante todo o ciclo de desenvolvimento da cultura, bem como a produtividade do algodoeiro no sistema de cultivo convencional. As dimensões das parcelas foram 24 m de largura x 100 m de comprimento em ambos os sistemas de semeadura, para os ensaios de deposição e cobertura. Para avaliação da deposição e cobertura foram escolhidas, ao acaso, 10 plantas e, de cada uma delas removida uma folha do ápice e outra folha da base da planta / Chemical control has been an essential practice on the pest management of cotton crop to reduce productivity losses. In order to promote rational use of pesticides, this work was aimed to compare three spray technologies: air-assisted, assisted by air associated with electrically charged droplets and conventional spraying (without air and electric charge) combined with volume rates of 50 and 100L.ha-1, on spray deposition, coverage and in the effect of control insect pests and disease. The trials were conducted in a randomized blocks design with six treatments and four replications for evaluation of the deposition, coverage and effect on pests and disease. The spraying was carried out on two growth stages of plants conducted in spacing of 0.45 m and 0.90 m between plant rows of culture. For this, were used a self-propelled sprayer equipped with spray nozzles hollow cone, JA-1 (50L.ha-1) and JA-2 (100L.ha-1) at 828 kPa of work pressure. The effect of these technologies was evaluated on controlling of Pseudoplusia includens, Bemisia tabaci, Aphis gossypii, Spodoptera spp. and Thrips spp. and a fungal disease Ramularia areola all the development cycle of the culture as well as the yield in conventional tillage. The dimensions of the plots were 24 m wide x 100 m length in both sowing systems for deposition and coverage tests. To evaluate the deposition and coverage were selected at random 10 plants and, of each one removed one leaf from the apex and another leaf of the lower part of plant. The tracer dye Brilliant Blue FD & C No. 1 (0.3%), fluorescent pigment ColorLight (0.15%) and Lignosulfonate Vixilperse (0.015%) were the tracer mixture. In experiments in which we evaluated the effect of the treatments on controlling pests and disease, were installed plots of 24 m wide x 250 m length and then weekly samplings were carried out as required spraying

Doctor of Philosophy / Department of Grain Science and Industry / X. Susan Sun / With continued population growth, more food production will be required with lower resource inputs. A significant drain on resources is post-harvest loss due to insects, which results in loss of product, quality and market access, and increased grain spoilage. Aeration and fumigation are key tools to control insect growth in stored grains and grain foods. The implementation of aeration strategies in Australia is made difficult by the warm subtropical climate, meanwhile the success of fumigation is being threatened by the spread of insect resistance to the fumigant phosphine. This dissertation project seeks to improve the understanding of aeration and fumigation by modifying the Maier-Lawrence (M-L) 3D ecosystem model by adding insect growth equations and quantifying fumigant loss from sealed bulk grain silos. The improved model was used to examine aeration under Australian conditions, validate its capability to accurately describe fumigant concentrations during silo fumigation, determine the extent to which fumigations are influenced by operational variables and environmental conditions, and validate its capability to describe fumigant concentrations post-fumigation in order to investigate the time needed to clear a grain storage silo of fumigant in order to assure worker safety. Six aeration strategies were evaluated under Australian conditions. Of these strategies, two were found to be effective in lowering temperatures, i.e., fans were turned on when ambient temperature was less than 20oC, and less than internal grain temperature. The strategy based on temperature differential was the most effective because it cooled the interior of the grain mass with the least amount of energy (using the fewest fan run hours, and reaching 15oC an average of 11 days after than the fastest strategy). Using a 0oC temperature differential was the most effective strategy in terms of reducing insect growth. The expanded (M-L-P) model was then validated based on experimental fumigant concentrations. The model was effective in reproducing average fumigant concentrations and fumigant trends vertically through the grain mass, but was not able to reproduce lateral fumigant variations. Verifications of the model with two different periods of phosphine release (i.e., 24h and 30h) were tested. Based on a 24h phosphine release period the predicted Ct-product differed from the experimental value by 0.9%. A 30h release period predicted a Ct-product that differed by 4.3% from the experimental value but it was more accurate during the times of highest concentration. Increases in leakage reduced fumigant concentrations, but the size of the effect decreased as leakage grew. Increasing temperature and wind speed in the model led to decreased phosphine concentrations, with temperature changes having a more significant impact overall than wind speed changes for the conditions investigated. Decreasing silo surface area to volume ratio dampened the impact of changing weather conditions on phosphine concentrations. A fumigant venting experiment was conducted in a silo at Lake Grace, Australia, to investigate full scale desorption. Two equations estimating fumigant desorption were tested, with an average of 65.5% and -86.3% error. The length of venting periods was simulated to quantify hours needed to mitigate hazardous conditions. For the scenarios investigated 10 to 24 h of venting were needed to reduce residual fumigant concentration below 0.3 ppm depending on simulation assumptions.

The alfalfa weevil, Hypera postica (Gyllenhal) (Coleoptera: Curculionidae), remains a serious pest in Virginia despite being under complete biological control in the northeastern U.S. In 1996, a survey of 187 alfalfa fields in Virginia was initiated to determine the current pest status of alfalfa weevil and incidence of natural enemies. Fields located in the Piedmont region of the state had significantly higher alfalfa weevil pressure than those in the Shenandoah Valley and southwestern region. The dominant natural enemy of alfalfa weevil larvae was the parasitoid, Bathyplectes anurus (Thomson). Larval parasitization was lower in the Piedmont compared with the other regions. The entomopathogenic fungus, Zoophthora phytonomi, also killed weevil larvae in all regions. A more intensive ecological investigation of alfalfa weevil population dynamics and mortality was initiated in 1997 to determine why H. postica remains a pest in Virginia, particularly in the Piedmont region. Nine alfalfa weevil populations from three geographic locations were sampled and measured over a period of two years. Results showed that warmer winter temperatures in the Piedmont region contributed to a higher rate of alfalfa weevil oviposition compared with the Shenandoah Valley and southwestern mountains. Parasitization of adult weevils by Microctonus aethiopoides (Loan) was low in all regions of Virginia relative to rates reported in the northeastern U.S. This also contributes to relatively high alfalfa weevil fecundity in Virginia because a greater percentage of adults reproduce. Phenological asynchrony between M. aethiopoides and the alfalfa weevil may explain the low parasitism. The 1st generation of M. aethiopoides adults did not emerge until most of the overwintering alfalfa weevil adults had reproduced and died. A majority of alfalfa weevil eggs were laid before January at all locations in Virginia. Approximately half of the egg population survived to contribute to spring larval infestations. In the northern U.S., very few alfalfa weevil eggs survive the winter, and larval populations result primarily from spring-laid eggs. Mortality of larvae was high in Virginia and comparable to that reported in other states. Bathyplectes anurus was well-synchronized with alfalfa weevil and killed a high percentage of larvae. / Ph. D.

The parasitic weeds belonging to the genus Striga are among the world's most tenacious, prolific and destructive agricultural pests. Crop loss estimates due to Striga infestations can reach 100 percent. Furthermore, the weeds' affinity for low-fertility soils and low rainfall means that those farming the most marginal lands are most severely affected. Nonetheless, subsistence farmer have yet to adopt seemingly beneficial control practices to any appreciable degree. This paper develops a bio-economic model capable of identifying: (1) affordable, effective Striga control practices consistent with the resource constraints of subsistence farmers; and (2) barriers to the adoption of those practices. The model is comprised of two components: a biological component modeling Striga population dynamics, and an economic component representing the production opportunity set, resource constraints, and price parameters farmers face. The model is applied to two zones in Northwestern Mali, Sirakorola and Mourdiah, and solved using non-linear, dynamic programming. Data collected by the USAID IPM-CRSP/Mali project are used to specify the economic parameters of the model. A new technique for estimating the lower bound of a farmer's production planning horizon is also developed and employed in the application of the model to Sirakorola and Mourdiah. The results of several model scenarios indicate that the availability of information regarding the efficacy of Striga control practices is a primary barrier to their adoption by subsistence farmers. The movement of Striga seed between fields, however, is of limited importance. The "optimal control practices" identified by the model depend on the size and demographic composition of the production unit (UP), the zone in which the UP is located, and the cash budget available to the UP. At low budget levels, the model suggests planting millet without fertilizer at a high density in Sirakorola and a low density in Mourdiah. At high budget levels, the model suggests planting millet at a high density in both zones while applying urea. The benefits of adopting the optimal set of practices are presented in both nutritional and financial terms, and can reach as much as a ten-fold increase in the nutritional content of and financial returns to a harvest. / Ph. D.

Edamame (Glycine max (L.) Merr.), also known as vegetable soybean, is primarily grown and consumed in Asia. In recent years, the demand for edamame in the United States has risen due to its health benefits as an alternative, plant-based protein. Due to the lack of domestic production, most edamame is imported from Asia. In an attempt to increase domestic production, research efforts have begun in Virginia and other regions to develop cultivars and best management practices for growing edamame in the mid-Atlantic region. Beginning in 2018, edamame trials examining breeding lines and cultivars were conducted to look at their suitability for this region. These varieties were sampled and evaluated for insect and disease complexes as well as their implications on plant yield and quality. Most of the insects and diseases that were found were very similar to pest complexes commonly found in cultivated soybeans in Virginia. However, due to edamame being marketed as a vegetable, insects and diseases that caused unsightly blemishes or damage to the pods or seeds were most concerning. Multiple insects and diseases were present but some of the most important insects and diseases we observed from 2018-2020 were pod feeding stink bug (Hemiptera: Pentatomidae), as well as the diseases like purple seed stain, Cercospora kikuchii, and bacterial pustule, Xanthomonas axonopodis pv. glycines. From 2019-2021 an integrated pest management study was conducted to determine best management practices for minimizing insecticide applications while applying them at thresholds to control key pests. In three growing seasons, I was able to determine that pesticides can be limited prior to flowering while insecticide inputs will need to be increased after flowering to protect the pods from pests, specifically stink bugs. Additionally, from 2019-2021 insecticide and fungicide field trials were conducted to test different pesticides on their efficacy against pod damaging pests and diseases. The growing seasons between 2019 and 2021 resulted in varying insect and disease pressure that led to inconsistent results. However, insecticides such as cyclaniliprole and sulfoxaflor performed well compared to other treatments. Lastly in 2020-2021, corn earworm (Helicoverpa zea [Boddie], Lepidoptera: Noctuidae), an important soybean pest and most likely a major pest of edamame, was tested for pyrethroid susceptibility and resistance across the state using a bean-dip bioassay. Pyrethroid efficacy to control this pest across Virginia seemed to vary by location and year, however, the bean-dip bioassay proved to be a time-efficient strategy for further monitoring these populations in the coming years. / Doctor of Philosophy / Edamame, also known as vegetable soybean, is primarily grown and consumed in Asia. Due to the lack of domestic production, most edamame is imported from overseas. Edamame trials were conducted in Virginia beginning in 2018, to look at production practices suitable for growing this crop in the region. Scientists observed edamame to document insect and disease complexes as well as their implications on yield and quality. Most of the insects and diseases that were found were very similar to what is known to already occur in soybeans. However, due to edamame being marketed as a vegetable, insects and diseases that left blemishes or damage to the pod were most concerning. Multiple insects and disease were present but some of the most important insects and diseases we observed were pod feeding stink bug species as well as the diseases purple seed stain and bacterial pustule. In 2019-2021 a pest management study was conducted to determine best management practices for minimizing insecticide applications while applying them at thresholds to control key pests. We were able to determine that pesticide usage can be limited prior to flowering while they will need to be increased after flowering to protect the pods. Additionally, in 2019-2021 insecticide and fungicide field trials were conducted to determine the efficacy of materials against pod damaging pests and diseases. The growing seasons between 2019 and 2021 resulted in varying insect and disease pressure, however, several insecticides with reduced ecological impacts out preformed others. Lastly in 2020-2021, corn earworm, a major pest of soybean and presumable of edamame, was tested for pyrethroid susceptibility and resistance across the state using a bean-dip bioassay. Pyrethroid efficacy across Virginia seemed to vary by location and year but the bean dip bioassay method proved to be a time-effective strategy for monitoring the states corn earworm populations against insecticides.

State Integrated Pest Management (IPM) programs are often called on to demonstrate their impacts. While many studies demonstrate techniques for assessing various economic and environmental effects of IPM, the literature provides little guidance on incorporating the techniques to perform complete assessments of IPM programs. This thesis begins with a discussion of relevant economic and environmental techniques for IPM impact assessment. Next, impact assessment techniques that are widely accepted and analytically feasible are identified. These techniques are incorporated into comprehensive impact assessment frameworks for use by individuals charged with the assessment of state level IPM programs. The study concludes with case studies which show how the assessment protocols were applied to estimate and describe the impacts of the Pennsylvania and Massachusetts sweet corn IPM programs. / Master of Science

The two papers in this thesis are aimed at solving problems in Integrated Pest Management project, practice, and program evaluations. In the first paper, an evaluation design is constructed for the Onion ipmPIPE website, an onion pest information website. The Bayesian decision theoretic approach may not accurately model onion growers' pest management decisions throughout the season. Randomization of the treatment is possible, but an incomplete grower list proved to be a problem. The analysis shows that an instrumental variables approach may be the most appropriate method for estimating the impact of the Onion ipmPIPE website because its data needs are solved by using USDA-NASS surveying services. In the second paper, the challenge is to develop a practical method to measure benefits accruing to women from agricultural research using secondary data. Donors, governments and others are interested in determining how benefits from agricultural research accrue to women. We develop a three-step framework to identify women's crops and technologies. In step one, total potential benefits from research are estimated; step two allocates those benefits between men and women; step three, incorporates technology-specific parameters to refine the estimates of potential benefits. We apply this framework to Honduras and find that steps one and two provide the most information on the magnitude and distribution of benefits, but that refinements in step three can affect rankings of research program impacts on women. / Master of Science

Potato farmers in Ecuador rely on chemical inputs to manage pests and optimize yields. IPM techniques are recommended to lower production costs, reduce exposure to pesticides, and improve the long-term sustainability of the agriculture system. We conducted a survey of 109 potato farmers in Carchi, Ecuador that included 30 Farmer Field School (FFS) participants, 28 farmers who had been exposed to FFS-participants, and 51 randomly selected farmers. Using an ordered probit model, the data were analyzed to identify determinants and constraints of adoption. Access to information through FFS was the main determinant of adoption of IPM, followed by field days, pamphlets, and exposure to FFS-participants. The study looked at the relative cost-effectiveness of information dissemination methods and found that field days and pamphlets have strong impacts on adoption considering their low cost of implementation. The only significant household variable was household size, where larger households adopted less IPM. Per capita land holdings were not significant in the model. There is evidence of farmer-to-farmer diffusion from FFS to non-FFS farmers. Further research is necessary to evaluate the nature and quality of information transfer between farmers. The study was limited by the small sample size and non-random selection of farmer respondents. / Master of Science

Smallholder farmers in Honduras and the Trifinio region of Central America contend with poor roads and high transportation costs when making production decisions. Farmers select crop activities based on cost, revenue and profit but are constrained by labor requirements, cash requirements, food security concerns, and input and output market access. Market access is directly related to distance to market. Distance to market increases the cost of inputs, increases transportation costs, and reduces the effective price farmers receive for outputs. We conduct two analyses to study the impact of distance to market on crop and technology choices. We utilize a household survey to analyze the determinants of fruit and vegetable production and market participation. Probit and multinomial logit models are employed to analyze the impact of distance to market and other variables on fruit and vegetable production. Results indicate that as distance to market increases, the probability of fruit and vegetable production for consumption increases and the probability of fruit and vegetable production for sale at market decreases. In a second paper, we utilize data from extension agencies, research institutions, a household survey, and expert opinions to model a representative Honduran farm. With linear programming, we analyze the crop and technology mix selected by the farm given changes in distance to the output market, changes in distance to the input market, food security concerns, and labor market participation. We focus specifically on integrated pest management (IPM) technologies. Results indicate that beyond a specific distance, vegetable production ceases, while staple crop production remains profitable. Additionally, a combination of low, medium, and high-technology crop activities is selected by a profit-maximizing farm. Even far away from the market, medium and high-technology crop activities are selected. Overall, these two studies indicate that distance to market is negatively related to fruit and vegetable production. A reduction in transportation costs and an increase in the prevalence of less input-intensive integrated pest management techniques may increase the incidence of fruit and vegetable production and market participation in Trifinio and Honduras. / Master of Science

Tuta absoluta, a member of the moth family, causes devastating yield loss to tomato farmers around the world. Its recent migration into the tomato fields of Nepal puts tomato farmers at a high risk of yield loss. In response, chemical pesticide use by Nepali farmers is increasing. Integrated pest management (IPM) practices have been implemented in hopes of reducing the frequency of chemical pesticide use while controlling yield risks. This study examines the extent and determinants of Tuta absoluta IPM adoption and its effect on the frequency of pesticide use for Nepali tomato farmers. Primary data was collected from four-hundred and one households in four districts throughout Nepal. Two levels of IPM practices were assessed, simple and complex, based on the need for additional knowledge and tools. An instrumental variable probit analysis was used to analyze the determinants of IPM adoption. Household distance to nearest agricultural extension office was a significant factor decreasing the likelihood of the adoption of complex practices. Amount of land dedicated to tomato production, membership status of the primary decision maker, IPM training regarding Tuta absoluta practices and severity of Tuta absoluta were found to increase the likelihood of the adoption of complex practices. In order to analyze pesticide use, a simple linear regression was used. Primary decision maker's age, gender, and education level were significant determinates to decrease the amount of expenditures spent on chemical pesticides to control for Tuta absoluta. IPM adoption level, amount of land dedicated to tomato production and severity of Tuta absoluta damage were significant determinates to increase the amount of expenditures spent on chemical pesticides to control for Tuta absoluta. / Master of Science / Tuta absoluta, a member of the moth family, causes devastating yield loss to tomato farmers around the world. Its recent migration into the tomato fields of Nepal puts tomato farmers at a high risk of yield loss. In response, chemical pesticide use by Nepali farmers is increasing. Integrated pest management (IPM) practices have been implemented in hopes of reducing the frequency of chemical pesticide use while controlling yield risks. This study examines the extent and determinants of Tuta absoluta IPM adoption and its effect on the frequency of pesticide use for Nepali tomato farmers. Data was collected from four-hundred and one households in four districts throughout Nepal. Different economic tools were used to conduct the analyses. Results show the farther a household is to the near agricultural extension office, the less likely a household is to adopt complex practices. An increased amount of land dedicated to tomato production, the primary decision maker being a member of a marketing or community organization, the primary decision maker having attended IPM training regarding Tuta absoluta practices and the greater the severity of Tuta absoluta in the household tomato fields, the more likely a household is to adopt complex practices. Contrary to one of the goals of IPM practices, this study shows complex adopters use more chemical pesticides than simple adopters. Results this study shows a need for further education of the relationship between IPM practices and the use of chemical pesticides.