OPTIMAL PEST CONTROL IN FLORICULTURE PRODUCTION OF ORNAMENTAL CROPS

We develop a conceptual bioeconomic model of floriculture production, wherein optimal decision rules depend on an intertemporal economic objective to maximize profits subject to economic and biological processes. The necessary conditions highlight intertemporal tradeoffs between aesthetic benefits and expected future net benefits of insect stocks, which have important policy implications.Research Methods/ Statistical Methods,

Automatic Calibration Tool for Hydrologic Simulation Program-FORTRAN Using a Shuffled Complex Evolution Algorithm

Hydrologic Simulation Program-Fortran (HSPF) model calibration is typically done manually due to the lack of an automated calibration tool as well as the difficulty of balancing objective functions to be considered. This paper discusses the development and demonstration of an automated calibration tool for HSPF (HSPF-SCE). HSPF-SCE was developed using the open source software “R”. The tool employs the Shuffled Complex Evolution optimization algorithm (SCE-UA) to produce a pool of qualified calibration parameter sets from which the modeler chooses a single set of calibrated parameters. Six calibration criteria specified in the Expert System for the Calibration of HSPF (HSPEXP) decision support tool were combined to develop a single, composite objective function for HSPF-SCE. The HSPF-SCE tool was demonstrated, and automated and manually calibrated model performance were compared using three Virginia watersheds, where HSPF models had been previously prepared for bacteria total daily maximum load (TMDL) development. The example applications demonstrate that HSPF-SCE can be an effective tool for calibrating HSPF

Soil Moisture Workshop

The Soil Moisture Workshop was held at the United States Department of Agriculture National Agricultural Library in Beltsville, Maryland on January 17-19, 1978. The objectives of the Workshop were to evaluate the state of the art of remote sensing of soil moisture; examine the needs of potential users; and make recommendations concerning the future of soil moisture research and development. To accomplish these objectives, small working groups were organized in advance of the Workshop to prepare position papers. These papers served as the basis for this report

Selective Utilization of Microhabitats by Web-building Spiders

Natural enemies are members of complex ecological communities, and their ability to contribute to the biological control of pest organisms is strongly influenced by a convoluted network of ecological interactions with many other organisms within these communities. Researchers must develop an understanding of the mechanisms that shape trophic webs to predict and promote top-down effects of predators. The behavior of predators can have a strong influence on their potential as biological control agents. Web-building spiders are a useful example organism for the study of natural enemy behavior because of the experimentally tractable nature of their foraging behavior. Specifically, patterns in microhabitat utilization and web construction by spiders provide insights into foraging behavior and pest-suppression potential. In field collections, spiders were found to utilize microhabitats in a species-specific manner. Molecular gut-content analysis and a mathematical model showed that two spiders belonging to different web-building guilds differed in their dependence on microhabitat-specific prey activity-densities. In particular, the sheet-weaving guild constructed webs in microhabitats with the highest densities of springtails (Collembola). High dependence on this non-pest prey also correlated with evidence of increased intraspecific competition, and implies a potential negative effect of springtails on the consumption of pest insects, such as aphids. In laboratory two-choice assays, sheet-weaving spiders selected microhabitats and constructed webs in a flexible, stepwise manner, which allowed spiders to regulate their investment of silk resources to match the profitability of the microhabitat. Spiders also exhibited prey-specific shifts in foraging behavior, constructing webs in the presence of mobile, non-pest springtails, but utilizing active foraging tactics in the presence of sedentary, pest aphids. However, in factorial no-choice assays, pest-consumption rates were not significantly affected by the presence of non-pest springtails, indicating that prey-specific foraging-mode shifts are compatible with biological control. From these results, it is clear that the flexible foraging behavior of web-building spiders has a strong influence on their roles in ecological communities and their position within food webs. This dissertation highlights the importance of understanding the nuances of natural-enemy behavior for properly assessing and promoting biological control services