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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Studies on the biology and mortality of the carrot fly, Psila rosae F. (Diptera:Psilidae)

Vincent, Julia January 1999 (has links)
Field and laboratory experiments were done to quantify the effects of high temperature and low soil moisture on the mortality of the immature stages of the carrot fly (Psila rosae F.). Field experiments related fly numbers to egg density and determined the period within each 8-10 week fly generation that resulted in most crop damage at harvest. Population monitoring: From 1995-1998, all stages of the carrot fly were monitored. No third fly generation was observed and no first-instar larvae were found after the end of September. Periods of high mortality were identified. [~gg mortality: Mortality was related linearly to the mean maximum soil temperature at 1 cm depth during egg development (m = 8.4t -167.3; m = % mortality, t = temperature). Under controlled conditions, eggs in dry soil died sooner at higher temperatures (>25°C) than eggs in moist soil. Fully developed eggs were more susceptible to adverse abiotic conditions than newly-laid eggs. Larval mortality: Up to 90% of first-instar larvae were killed by low soil moisture in the field. This mortality was related to the length of time larvae were exposed to dry soil conditions (m = 2.6 + 17.6d; m = % mortality, d = no. of days in dry soil). Relationship between numbers offlies and egg density: A linear relationship (e = 0.32 + 0.89[; e = log no. eggs, f = log no. flies) was identified between the numbers of carrot flies caught on sticky traps and the numbers of fly eggs recovered from carrot crops. Critical egg-laying period: Within a generation, the critical egg-laying period when most damage was caused was between 10-20 days. This coincided with the peak in fly numbers. Rearing method: A robust rearing method was developed for producing a regular supply of adults. Approximately 50% of eggs inoculated onto growing carrots gave rise to pupae.
2

Studies on some of the important features in the biological relationship between the bacterial parasite Pasteuria penetrans and its host Meloidogyne SPP

Silva, Primalie De January 1992 (has links)
No description available.
3

Involving farmers in the design of low-input control programme for sesame flea beetle (Alocypha bimaculata, Jacoby) in S.E. Tanzania

Mponda, O. K. K. January 1996 (has links)
No description available.
4

Tranors förekomst på fält kring Tåkern påverkas av vägar, vatten, byggnader, träd och buskage / Roads, water, buildings, trees and shrub affect the occurrence of the Eurasian crane in fields connected to Lake Tåkern

Wohlfarth Hasle, Inger-Marie January 2016 (has links)
Every year the Eurasian crane travel from northern Africa to northern Europe and Asia. On their migration route they need to rest and often choose places around shallow lakes in agriculture landscapes. During their time in these resting sites the cranes forage in agriculture fields surrounding the lakes, which often cause crop-damage and thereof also financial loses. The last 30 years the population has increased radically, resulting in more extensive crop-damage. This study was set out to gain a better understanding how these migrating cranes choose sites to forage, based on four environment factors: roads, water, buildings, trees and shrub. A study-area in north of Lake Tåkern was selected and during six days in the spring all the cranes in the area were counted and marked on a map. The results showed that the factors affected the occurrence of cranes in the fields. They wanted to be close to shallow water and keep a distance to buildings, roads, trees and shrub. The cranes often spend the night in shallow water and search for food in the area close by to not lose too much energy, which probably was the main reason for the birds to stay close to the water. The distance to buildings and roads suggests that the cranes want to avoid interference from humans and the distance to trees and shrub that they want to have a good awareness of their surroundings. Through this understanding, areas with higher risk to attract groups of cranes can more easily be identified.
5

Spatial Distribution of Human Elephant Conflict (HEC) and Characterization of Crop-Raiding Elephants in Kasigau Region, Kenya

Kagwa, Simon Kasaine 01 August 2011 (has links)
Human-elephant conflict (HEC) is complex and a serious elephant conservation concern across Africa and Asia where elephants are found. HEC occurs whenever people and elephants share common interests. For HEC to be ameliorated and elephant conservation to be successful locally and regionally, the distribution and implications of HEC should be understood. The purpose of this study was to determine the spatial distribution of HECs and characterize elephant herds in terms of herd size responsible for crop-raiding in Kasigau. The study was generally guided by two working a priori hypotheses: (1) farms near the bush edge or livestock watering points will experience more crop raiding incidences than those farther away, and (2) given the geographical differences, the total cost of damage to crops sustained in all the farms will be different across the seven villages. For hypothesis 1, the distances of random farms to the bush and to the bush edge were mapped and measured on Google EarthTM. Results of the study showed that there were differences in the distribution of the distances from the bush and from water for farms that experienced damage and a random selection of farms (p < .0001). Additionally, total cost of damage to crops (Kruskal-Wallis; p < 0.0001), average cost of damage to crops per acre per incursion (Kruskal-Wallis ANOVA; p = 0.0255) and mean cost of damage to crops and facilities (Kruskal-Wallis ANOVA; p < 0.0001) were also found to be statistically different across all the villages. Four villages (Bungule,Ngambenyi, Makwasinyi, and Kisimenyi) sustained high total cost of damage to crops and average cost of damage to crops per acre per incursion indicating that these villages had similar elephant pressure. Ngambenyi village sustained the greatest cost of damage to crops while Kiteghe recorded the greatest average cost of damage to crops per acre per incursion. A posteriori hypotheses included: (1) there will be seasonal distribution of elephant attacks on farms. Results showed that the proportion of total crop-raiding incidents was different during wet and dry seasons in my study period (X2 = 5.49, df = 1, p < .019) with the greatest occurrence of attacks taking place in February, which coincided with crop maturity. This indicates that crop raiding incidents were most common during harvesting time. This result coincides with what was reported elsewhere. (2) there will be difference in the number of crop-raiding incidents by single and multiple elephant responsible for crop incursions in Kasigau. Results demonstrated that the number of crop-raiding incidents by single and multiple elephants were significantly different (X2 = 329.1037; df = 1; p < .0001). A total of 163 (72%) farm incursions were caused by elephant herds comprising multiple individuals while single elephants were responsible for 62 crop-raiding incidents, or 28% of total farm incursions. 100% (225 incursion) of crop incursions reported occurred during the night.
6

Habitat selection by sympatric ungulates in an agricultural landscape : implications for disease transmission and human-wildlife conflict

2013 January 1900 (has links)
As areas of agricultural production expand worldwide, complex zones of wildlife-agriculture interface present numerous benefits and challenges to farmers and wildlife managers. In western Canada, free-ranging elk (Cervus canadensis), mule deer (Odocoileus hemionus), and white-tailed deer (Odocoileus virginianus) make frequent use of cereal, oilseed, and pulse crops. However, cervid use of annual crops presents substantial socio-economic concerns for producers. Additionally, use of crops may facilitate cervids co-mingling and increase the risk of intra- and inter-specific transmission of chronic wasting disease (CWD). The purpose of my thesis research was to determine the key environmental factors influencing the selection of agricultural crops by elk, white-tailed deer, and mule deer, analyze overlap in species’ selection, and develop predictive models to identify the spatial distribution of crop damage risk. In this study, I analyzed 19,069 damage claims paid by Saskatchewan Crop Insurance Corporation to Saskatchewan farmers for confirmed losses to annual crops (cereals, oilseeds, pulses) from 2000-2012 by elk, mule deer, and white-tailed deer. These data were used to conduct species-specific ecological niche factor analyses (ENFAs), which relate habitat variables within damaged sites to that of the surrounding landscape. The key habitat variables influencing selection of annual crops were then incorporated into resource selection probability function (RSPF) models. These models characterize and predict the probability of crop damage by elk, mule deer, and white-tailed deer, and each possible dual species combination. By integrating damage probability values and historical monetary values of regional crop production, I evaluated the risk of annual crop damage by each of the three species, and dual species combinations, across all sections of agricultural land in Saskatchewan. The ENFAs revealed that elk and white-tailed deer selected for areas where a high proportion of farmland is seeded to oats, barley, canola, and alfalfa, while avoiding areas farther from protected areas, with a high density of paved or unpaved roads and a high proportion of open grassland. Alternately, mule deer favoured open grasslands, shrublands, and areas with a greater density of streams or water bodies, while avoiding areas where a high proportion of farmland is seeded to oats, canola, flaxseed, wheat, and barley. Areas at highest risk for annual crop damage by elk bordered the northern edge of the study area; mule deer damage risk was highest in south-western and central Saskatchewan; while white-tailed deer damage risk was highest in north-eastern and north-central areas of the province. Identifying these specific associations between landscape variables, rates of crop damage, and associated species overlap may provide an important opportunity for agencies to develop cooperative management strategies to efficiently allocate mitigation resources. Efforts to prevent the selection of cereal, oilseed, and pulse crops by free ranging elk, mule deer, and white-tailed deer in Saskatchewan could prove to be a valuable step in not only minimizing crop damage and maintaining wildlife tolerance in rural communities, but also in managing the spread of chronic wasting disease throughout western Canada.
7

Bird Species in Urban and Agricultural Landscapes : Bird diversity patterns along an urbanisation gradient and crop damage caused by birds on the Deccan Plateau, India

Kale, Manoj Ashokrao January 2014 (has links)
The major human activities that have transformed the Earth include agriculture and urbanization. The present study was conducted to contribute to a description of the effect on birds of urbanization and agriculture in an Indian region. Terrestrial bird assemblages were censused along a five-stage urbanisation gradient between January and April 2010-2013 near the city of Amravati, on the Deccan Plateau, Central India. Altogether, 89 species of birds were recorded, with the highest species richness in the rural areas (67 species) and lowest in the urban stage (29 species). The assemblages were significantly nested in all the five stages. Maximum cumulative species abundance (12 399 individuals over four years) was found in the urban stage, and was due to the constant presence of large groups of Rose-ringed Parakeets (Psittacula krameri). The lowest bird abundance was found in the industrial zone (4837 in total), where there was also a nearly two-fold decrease from 2010 to 2013. Thirty-six species demonstrated significant variation in their densities at least in one stage and between at least two months (p&lt;0.05). Densities of 13.9% (n=5) of those species varied significantly in two stages, that of Copsychus saularis in three stages, and of Phoenicurus ochruros, in all five stages. Urban, suburban, periurban and forest stages were characterised by relatively stable species densities (significant changes observed only for 17.2% (n=5), 17.1% (n=6), 12.9% (n=7), and 17.8% (n=16) species, respectively). The additive diversity partitioning indicated that of the overall diversity (gamma-diversity), alpha diversity (within transects located within one stage) contributed 50.1% to the total diversity, and the controbution of within-stage variability was small (2.7%). Additionally, censuses on cultivated fields were taken. In two areas under mixed cropping systems, 53 bird species were identified in the two years period between June and December, 2011 and 2012. Out of the 53 detected species, only 14 were common (recorded at ≥50% of visits). Twenty-one species were recorded at Zadgaon in crops of tur (Cajanus cajan), cotton (Gossypium arboreum) and soybean (Glycine max). Nineteen species were recorded at Bhankhed in jawar (Sorghum bicolor), cotton and mung bean (Phaseolus aureus). At Zadgaon, territorial activity was observed in four species: the House Sparrow (Passer domesticus), Jungle Babbler (Turdoides striata), Yellow-eyed Babbler (Chrysomma sinense) and Red-wattled Lapwing (Vanellus indicus). The study indicated that four bird species were found under high risk, thirteen species at medium risk and eight species at low risk due to pesticide applications in croplands. The extent of crop damage in fields of groundnut, pearl millet, peas, sorghum, and sunflower was assessed by doing actual field censuses. The sustainable solution for reducing crop damage is a need for the farmers and such techniques will help to avoid direct or indirect effects of use of lethal bird control techniques on bird species diversity. / <p>QC 20141022</p>
8

Quantifying the impacts of inundated land area on streamflow and crop development

Stuart D Smith (10292588) 06 April 2021 (has links)
<p>The presented work quantifies the impacts of inundated land area (ILA) on streamflow and crop development in the Upper Midwest, which is experiencing a changing climate with observed increases in temperature and precipitation. Quantitative information is needed to understand how upland and downstream stakeholders are impacted by ILA; yet the temporal and spatial extent of ILA and the impact of water storage on flood propagation is poorly understood. Excess water in low gradient agricultural landscapes resulting in ILA can have opposing impacts. The ILA can negatively impact crop development causing financial loss from a reduction or total loss in yield while conversely, ILA can also benefit downstream stakeholders by preventing flood damage from the temporary surface storage that slows water movement into channels. This research evaluates the effects of ILA on streamflow and crop development by leveraging the utility of remotely sensed observations and models.</p><p> </p><p>The influence of ILA on streamflow is investigated in the Red River basin, a predominantly agricultural basin with a history of damaging flood events. An inundation depth-area (IDA) parameterization was developed to parameterize the ILA in a hydrologic model, the Variable Infiltration Capacity (VIC) model, using remotely sensed observations from the MODIS Near Real-Time Global Flood Mapping product and discharge data. The IDA parameterization was developed in a subcatchment of the Red River basin and compared with simulation scenarios that did and did not represent ILA. The model performance of simulated discharge and ILA were evaluated, where the IDA parameterization outperformed the control scenarios. In addition, the simulation results using the IDA parameterization were able to explain the dominant runoff generation mechanism during the winter-spring and summer-fall seasons. The IDA parameterization was extended to the Red River basin to analyze the effects of ILA on the timing and magnitude of peak flow events where observed discharge revealed an increasing trend and magnitude of summer peak flow events. The results also showed that the occurrence of peak flow events is shifting from unimodal to bimodal structure, where peak flow events are dominant in the spring and summer seasons. By simulating ILA in the VIC model, the shift in occurrence of peak flow events and magnitude are better represented compared to simulations not representing ILA.</p><p> </p><p>The impacts of ILA on crop development are investigated on soybean fields in west-central Indiana using proximal remote sensing from unmanned aerial systems (UASs). Models sensitive to ILA were developed from the in-situ and UAS data at the plot scale to estimate biomass and percent of expected yield between the R4-R6 stages at the field scale. Low estimates of biomass and percent of expected yield were associated with mapped observations of ILA. The estimated biomass and percent of expected yield were useful early indicators to identify soybean impacted by excess water at the field scale. The models were applied to satellite imagery to quantify the impacts of ILA on soybean development over larger areas and multiple years. The estimated biomass and percent of expected yield correlated well with the observed data, where low model estimates were also associated with mapped observations of ILA and periods of excessive rainfall. The results of the work link the impacts of ILA on streamflow and crop development, and why it is important to quantify both in a changing climate. By representing ILA in hydrologic models, we can improve simulated streamflow and ILA and represent dominant physical process that influence hydrologic responses and represent shift and seasonal occurrence of peak flow events. In the summer season, where there is an increased occurrence of peak flow events, it is important to understand the impacts of ILA on crop development. By quantifying the impacts of ILA on soybean development we can analyze the spatiotemporal impacts of excess water on soybean development and provide stakeholders with early assessments of expected yield which can help improvement management decisions.</p>
9

Trouble in the air: Farmers’ perceptions of risk, self-efficacy, and response efficacy regarding herbicide drift

Folck, Alcinda L. January 2017 (has links)
No description available.

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