Modelling biomass production and yield of horticultural crops: a review

This paper examines the impacts of climate change on cassava production in Africa, and questions whether cassava can play an important role in climate change adaptation. First, we examine the impacts that climate change will likely have on cassava itself, and on other important staple food crops for Africa including maize, millets, sorghum, banana, and beans based on projections to 2030. Results indicate that cassava is actually positively impacted in many areas of Africa, with −3.7% to +17.5% changes in climate suitability across the continent. Conversely, for other major food staples, we found that they are all projected to experience negative impacts, with the greatest impacts for beans (−16% ± 8.8), potato (−14.7 ± 8.2), banana (−2.5% ± 4.9), and sorghum (−2.66% ± 6.45). We then examined the likely challenges that cassava will face from pests and diseases through the use of ecological niche modeling for cassava mosaic disease, whitefly, brown streak disease and cassava mealybug. The findings show that the geographic distribution of these pests and diseases are projected to change, with both new areas opening up and areas where the pests and diseases are likely to leave or reduce in pressure. We finish the paper by looking at the abiotic traits of priority for crop adaptation for a 2030 world, showing that greater drought tolerance could bring some benefits in all areas of Africa, and that cold tolerance in Southern Africa will continue to be a constraint for cassava despite a warmer 2030 world, hence breeding needs to keep a focus on this trait. Importantly, heat tolerance was not found to be a major priority for crop improvement in cassava in the whole of Africa, but only in localized pockets of West Africa and the Sahel. The paper concludes that cassava is potentially highly resilient to future climatic changes and could provide Africa with options for adaptation whilst other major food staples face challenges.

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Is Cassava the Answer to African Climate Change Adaptation

We demonstrate the use of matrix models to assess the impact of biological control and other pest management strategies with a case study of Carduus nutans (nodding thistle) in New Zealand. Modeling can facilitate the choice of the best control agents, improve evaluation of biocontrol attempts, and assist in the design of integrated pest management plans. Field data for ∼8000 mapped C. nutans plants at two sites in New Zealand were used to develop size-structured matrix models. The matrix models confirm that both populations of C. nutans were increasing in number, as is expected of a noxious weed in its invasion phase. Elasticity analysis indicated that seed/seedling and small-plant/seed transitions were more crucial to population growth than rosette survival rates. However, simulations of attack by the biocontrol agent Rhinocyllus conicus (nodding thistle receptacle weevil) showed that seed losses of ∼69% would be required to make the populations decrease in size, far more than the observed losses of 30–...

Estimating biocontrol agent impact with matrix models: carduus nutans in new zealand

McCauley et al. (1988) have compared the predictions of simple traditional predator-prey models with the patterns of abundance exhibited by Daphnia and its algal food supply. On one hand, the data gathered from several natural lakes of different nutrient status show a concurrent increase of phytoplankton and Daphnia biomasses. On the other hand, all models considered by McCauley et al. (1988) predict that any increase of the parameters quantifying algal productivity would lead to an increase in Daphnia biomass only. The algal biomass should not respond to a productivity increase. To resolve this contradiction, the authors suggest that enrichment affects not only algal production but also Daphnia parameters. The four models considered by McCauley et al. (1988) can be written in a single generalized form:

Variation in Plankton Densities Among Lakes: A Case for Ratio-Dependent Predation Models

The discovery of the soybean aphid, Aphis glycines Matsumura, in U.S. soybean production systems in 2000 has provided a unique opportunity to study the interaction of a new invader with existing natural enemy communities. One research thrust has been examining the role of predators in soybean aphid dynamics in the Midwest. We discuss the roles of predatory arthropods in field crops and set forth a conceptual model that we have followed to identify key predators in the soybean aphid system. We identify Orius insidiosus (Say) and Harmonia axyridis (Pallas) as potentially key predators and show our findings on their phenology in soybean fields and their impact on soybean aphid population dynamics. Finally, we discuss how this information can be used in integrated pest management programs for soybean aphid and point to gaps in our knowledge where future studies are needed.

https://bioone.org/journals/Annals-of-the-Entomological-Society-of-America/volume-97/issue-2/0013-8746(2004)097[0240:SAPATU]2.0.CO;2/Soybean-Aphid-Predators-and-Their-Use-in-Integrated-Pest-Management/10.1603/0013-8746(2004)097[0240:SAPATU]2.0.CO;2.pdf

Soybean Aphid Predators and Their Use in Integrated Pest Management

Analysis of Biological Control of Cassava Pests in Africa. II. Cassava Mealybug Phenacoccus manihoti

SUMMARY (1) A model for the growth and development of cassava, Manihot esculenta Crantz, as modified by weather, soil nitrogen and water is described, and used in later papers to evaluate damage by exotic cassava pests and the effectiveness of control by natural enemies. (2) Analogous relationships between trophic level models at the population and per capita levels were exploited to develop a model that has a common mathematical form across trophic levels. (3) The distributed delay model of Manetsch (1976) was used as the conceptual shell in describing the population dynamics of populations and of organism organ levels (e.g. leaves of plants, ova in animals). (4) The Frazer-Gilbert functional response model from animal ecology was modified to predict rates of photosynthesis and nitrogen and water uptake in plants. (5) Dry-matter partitioning in cassava as affected by solar radiation, temperature, and water and nitrogen stress was simulated and compared with three sets of field data.

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Analysis of biological control of cassava pests in Africa: I. Simulation of carbon, nitrogen and water dynamics in cassava

SUMMARY (1) The interactions of cassava green mite, Mononychellus tanajoa (Bondar) s.l., and cassava, Manihot esculenta Crantz, under West African weather and soil conditions were examined using a simulation model. (2) Field studies had demonstrated the effects of plant and leaf age and rainfall-induced mortality on M. tanajoa population growth. In the absence of effective natural enemies, the model explains, in order of importance, the effects of rainfall, drought stress via the host-plant, food availability (production and persistence of new foliage) and leaf quality (N concentration) on M. tanajoa population growth. (3) Rainfall-induced mortality greatly reduced M. tanajoa populations in the rainy season, drought and N stresses acting indirectly via food availability being most important in the dry season. (4) The combined effects of M, tanajoa feeding and water and N stress on cassava tuber yield were assessed.

/pdf/analysis-of-biological-control-of-cassava-pests-in-africa-ucenkrdh1o.pdf

Analysis of biological control of cassava pests in Africa: III. Cassava green mite Mononychellus tanajoa

A distributed delay age structure model is presented for plants and insects that describes the dynamics of per capita energy (dry matter) acquisition and allocation patterns, and the within-organism subunit (e.g. leaves, fruit, ova) number dynamics that occur during growth, reproduction, and development. Four species of plants (common bean, cassava, cotton, and tomato) and two species of insects (pea aphid and a ladybird beetle) are modeled. A common acquisition (i.e. functional response) submodel is used to estimate the daily photosynthetic rates in plants and consumption rates in pea aphid and the ladybird beetle. The focus of this work is to capture the essence of the common attributes between trophic levels across this wide range of taxa. The models are compared with field or laboratory data. A hypothesis is proposed for the observed patterns of reproduction in pea aphid and in a ladybird beetle.

/pdf/energy-acquisition-and-allocation-in-plants-and-insects-a-htweppa5u5.pdf

C. K. Ellis

Papers

Analysis of Biological Control of Cassava Pests in Africa. II. Cassava Mealybug Phenacoccus manihoti

Analysis of biological control of cassava pests in Africa: I. Simulation of carbon, nitrogen and water dynamics in cassava

Analysis of biological control of cassava pests in Africa: III. Cassava green mite Mononychellus tanajoa

Energy acquisition and allocation in plants and insects: a hypothesis for the possible role of hormones in insect feeding patterns

A physiologically-based tritrophic metapopulation model of the African cassava food web