A simple age-specific energetics (calories or biomass) model for the growth and development, reproduction, respiration, ageing, and intrinsic survivorship as a function of temperature and per capita energy availability for pea aphid (Acyrthosiphon pisum (Harris)) is reported. The ratio of energy supply–demand is used to scale all of the rates in the model. The maximum demand for energy based upon current state values is used to drive the Frazer–Gilbert functional response model (i.e. food acquisition), which is a component of the metabolic pool model used to assimilate energy to growth, reproduction, respiration, and egestion. The extensive data sets on pea aphid energetics published by Randolph et al. (1975) were used to develop the model. As the model estimates reproduction (Mx) and survivorship (Lx) values, extensive published age-specific life-data sets on pea aphids are used to test it. The results suggest:(1) the lower thermal threshold for development is raised and the upper threshold is lowered as food resources are decreased(2) the temperature-dependent rate of development is slowed with decreasing energy resources(3) the size of individuals and reproduction become smaller as temperature approaches the upper and lower thermal thresholds.A simple model for multitrophic level interactions incorporating the acquisition and assimilation functions is presented.

Can. Ent. 113: 21-33 (1981) A simple model for growth and development of the ladybird-beetle (Hippodamia convergens G-M.) which parritions aphid biomass eaten into components of excretion, assimilation, growth and/or reproduction, and metabolic costs associated with searching and maintenance respiration is reported. All parameters in the model were estimated from simple minimal laboratory experiments, and have biological and/or physical meaning. The effects of predator nutrition on aging, survival, and emigration were also modelled. Most rates in the model for growth, reproduction, and respiration are controlled by the interplay between prey consumption and maximum prey biomass demands. The model for biomass flow is related to standard predator/prey theory.

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An energy-flow multitrophic-level model incorporating acquisition (functional response) and assimilation (metabolic pool model) functions and stochastic development is proposed and put into historical perspective. The model is general for each trophic level and for all subcomponents. Prey demand drives the functional response model, while food supply–demand determines all intrinsic rates in the model. The model is used to explore the theoretical properties of a multitrophic system comprising alfalfa, blue aphids, pea aphids, a host-specific parasitoid, and two predators (lady beetles, green lacewings). The model shows:(1) the importance of the resource base on higher trophic level dynamics and vice versa(2) the stability properties of different combinations of species(3) the role of parasitoids and predators in population regulation in this system(4) how food acquisition and respiration as functions of temperature and per capita resource interact to determine the rate of population growth(5) that extreme caution must be used in extrapolating theoretical results to field situations.

It aims at increasing the efficiency of agricultural research in the region so as to facilitate economic growth, food security, and export competitiveness through productive and sustainable agriculture. Background The background to regional collaboration in agricultural research can be traced to the early 1980s when scientists from the national programs began working together. To run these networks, regional steering committees were put in place to consider and approve annual work plans. Membership was drawn from the national coordinators for research, as well as the scientists from the international research centers. With time, these early networks evolved and came to be regarded as one way of achieving economies of scale and facilitating technology spill-overs across national boundaries. It was upon this that the idea of a regional association was initiated and built. Given the many commodities and factors which each national system had to handle and the need for increased efficiency and effectiveness in utilizing scarce resources, it was agreed that a regional strategy for agricultural research and research-related training be implemented. So, in September 1994, the Memorandum of Agreement that established ASARECA was signed and in October, that same year, the Executi"ve Secretariat became operational and is based in Entebbe, Uganda. The directors of the national agricultural research institutes in the ten member countries constitute the Committee of Directors, which is the highest governing body. The Committee provides policy oversight while the Executive Secretariat services it and implements its decisions under the guidance of the Chairman. Research Networks ASARECA carries out its activities through regional research networks, programs, and projects. Twelve of these are currently operational with seven due to begin operations in the next several months. However, it is important to note that before ASARECA came into existence, there was already some collaborative research within the region. This was brought under the ambit of ASARECA when it was established and it is carried out by the first-generation networks. These are the research networks on potato and sweet potato, agroforestry, root crops, and beans. The second-generation networks are those established in the 1990s; they are the research networks on banana, postharvest processing, animal agriculture, maize and wheat, highlands, technology transfer, agricultural policy analysis, and electronic connectivity. The new networks under planning are those on rice, plant genetic resources, sorghum and millet, soil and water conservation, coffee, agricultural information, and strengthening the capacity of NARis to manage regional programs. Preface This project was designed to devdop a case Study "protocol" or methodology for undertaking a rapid national market analysis of the supply and demand fur a specific commodity. The need for this type of information was based on the anticipated increase in market sector studies that will be undertaken by the new ASARECA...