Staff Publications

Staff Publications

  • external user (warningwarning)
  • Log in as
  • language uk
  • About

    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

    We have a manual that explains all the features 

Current refinement(s):

Records 1 - 20 / 26

  • help
  • print

    Print search results

  • export

    Export search results

  • alert
    We will mail you new results for this query: keywords==katoen
Check title to add to marked list
Recognition of Verticillium effector Ave1 by tomato immune receptor Ve1 mediates Verticillium resistance in diverse plant species
Song, Yin - \ 2017
University. Promotor(en): Bart Thomma; Pierre de Wit. - Wageningen : Wageningen University - ISBN 9789463437950 - 231
disease resistance - defence mechanisms - immunity - plant-microbe interactions - plant pathogens - verticillium dahliae - verticillium - tomatoes - solanum lycopersicum - receptors - genes - tobacco - nicotiana glutinosa - potatoes - solanum tuberosum - solanum torvum - humulus lupulus - cotton - gossypium hirsutum - transgenic plants - arabidopsis thaliana - ziekteresistentie - verdedigingsmechanismen - immuniteit - plant-microbe interacties - plantenziekteverwekkers - tomaten - receptoren - genen - tabak - aardappelen - katoen - transgene planten

Plant-pathogenic microbes secrete effector molecules to establish disease on their hosts, whereas plants in turn employ immune receptors to try and intercept such effectors in order to prevent pathogen colonization. Based on structure and subcellular location, immune receptors fall into two major classes; cell surface-localized receptors that comprise receptor kinases (RKs) and receptor-like proteins (RLPs) that monitor the extracellular space, and cytoplasm-localized nucleotide-binding domain leucine-rich repeat receptors (NLRs) that survey the intracellular environment. Race-specific resistance to Verticillium wilt in tomato (Solanum lycopersicum) is governed by the tomato extracellular leucine-rich repeat (eLRR)-containing RLP-type cell surface receptor Ve1 upon recognition of the effector protein Ave1 that is secreted by race 1 strains of the soil-borne vascular wilt Verticillium dahliae. Homologues of V. dahliae Ave1 (VdAve1) are found in plants and in a number of plant pathogenic microbes, and some of these VdAve1 homologues are recognized by tomato Ve1. The research presented in this thesis aims to characterize the role of the tomato cell surface-localized immune receptor Ve1, and its homologues in other diverse plant species, in Verticillium wilt resistance.

Organising trade : a practice-oriented analysis of cooperatives and networks trading cereals in South Mali
Mangnus, E.P.M. - \ 2015
University. Promotor(en): Cees Leeuwis, co-promotor(en): Sietze Vellema. - Wageningen : Wageningen University - ISBN 9789462574311 - 178
coöperaties - voedselcoöperaties - graansoorten - handel - katoen - geschiedenis - platteland - landbouw - agrarische handel - mali - west-afrika - cooperatives - food cooperatives - cereals - trade - cotton - history - rural areas - agriculture - agricultural trade - west africa


Farmer organisations have become the centrepiece of pro-poor market development strategies in Africa. Assumed to facilitate scale, quality of produce and professionalism they are regarded as a solution for farmers that are hampered from economic opportunities. In Mali public as well as private actors encourage farmers to trade through one specific organisational form, namely cooperatives. Nevertheless, in reality the landscape is much more diverse. A wide array of organisations can be observed and the models stimulated by external actors do not always succeed in improving the position of farmers. Considering the gap in knowledge, this dissertation poses the following question:

How and in what ways do people organise trading of cereals in South Mali?

The central aim of this thesis is to contribute to a better understanding of organisation of food trade in rural markets, by examining how and in what ways people in South Mali organise trade in cereals and sesame. Trading includes the procurement of cereals or sesame, organisation of finance, information gathering, bargaining, the organisation of transport and selling.

Organisation of trade has been studied from different angles. Studies taking a structural approach explain organisation as emerging from context. Studies that approach organisations from an instrumental perspective regard organisation as a means for efficiently solving a shared problem. Both strands provide insights for understanding organisational functioning and performance but leave open questions regarding how people organise to realise trading and why this results in organisational diversity. This thesis examines organising trade by adopting a practice-oriented approach, which has as entry point that organisation takes shape in the realization of everyday practice. Focus is on what people actually do to realise trading.

Two case study organisations are central to the study. Both are typical for how trade in rural Mali is organised. The first is a cooperative engaged in the trading of sesame in Miena, South-East Mali. The second is a cereal trading network in N’golobougou, in the centre of South Mali. Both provide an example of people collaborating and coordinating to perform trading and as such are excellent cases for tracing the formation of organisational traits that explain performance and diversity in trading cereals in South Mali.

Empirical Chapters

Chapter 2 presents a historical overview of how the organisation of trade of cereals and cotton at farmer level developed in Mali on extensive literature research. It focuses on the efforts of the Malian state to organise rural society, how producers responded, and how the interaction between the two shaped organisation. The analysis starts in the 18th century, in which cotton and cereal trade was intertwined and likewise organised. From the colonial period onwards, organisation dynamics in food and export crops evolved distinctly. For both sectors the most important events and changes are detailed. The chapter found that the political economy at stake influences the set of organisational options people can choose from and that imposed models rarely get adopted in practice.

Chapter 3 traces the emergence and development of the sesame cooperative in Miena. It builds on two strands of literature that emphasize the specific socio-historical context of an organisation. The first body highlights the resilience of existing relations and institutions by showing how these get reproduced in new organisations. The second body of literature claims that individuals involved in collective action have the capacity to influence which institutions get reproduced and which new ones get adopted, also called ‘blended’. To collect the data 35 in depth interviews with cooperative members, (ex) officials from the cotton company CMDT, local officers and NGO-workers active in the research location were collected over a period of three months. Time was spent at the weekly market, in village meetings and at peoples’ homes. Moreover 20 informal talks with villagers and traders on the market were afterwards noted down. Three distinct processes - the historical organisation of cotton farmers, the interaction between state and society and the local trade practices - are found to underlie the current functioning of the cooperative. This chapter shows how both the reproduction and blending happen purposively; in order to (continue) performance in trading.

Chapter 4 addresses the question: How do traders in Mali perform collectively? Following the methodological orientation, labelled as technography, the chapter zooms in on the use of skills and know-how by a group of people coordinating the collection and trade of cereals. Data were collected through 24 in-depth interviews with traders and 37 semi-structured interviews with pisteurs and interviews with key resource persons. Moreover, trade practices were observed during 10 market days in a row. The analysis shows that the success of the traders’ network can be explained by: (i) the use of skills and know-how for adapting to changing economic, social and environmental contexts; (ii) the network’s ability to select capable people and distribute the many trading tasks; and (iii) the network’s effective governance, based on a strict code of conduct specific to each role. The chapter shows how rules steering the distribution of tasks and collaboration in the traders’ network emerge out of the daily practice of trading.

Chapter 5 uses evidence from a network of cereal traders in the market of N’golobougou to examine how the characteristics of traders, their positions within different networks, and different kinds of relationships between traders influence performance in trading. 26 traders were extensively interviewed on the history, functioning and the size of their business. Semi-structured interviews focused on their relations in trading. A social network analysis (SNA) is applied to describe the positions of individual traders in the networks and the type of relations that link them. Qualitative analysis is used to understand the motivations underlying their position and collaboration. The findings demonstrate that trading is a complex and multifaceted activity. Within the network distinct networks have emerged to organise the collection of cereals, to arrange finance and to acquire information. Pre-existing social relations facilitate trading but do not guarantee individual success. Proven ability and reputation are equally important in cooperation and relate to the way powerful members of the network acquire a central position, which goes stepwise and takes time.


Collaboration is crucial for trading under the circumstances of rural Mali. Both case studies highlight the role of key individuals who spotted opportunities and mobilised others to collaborate. Different trading activities require specific skills, know-how and tools and people tend to specialise. Most skills are acquired in practice; few of them can be taught by instruction. Accordingly to what is present in terms of capacities, people’s availability and know-how, and tools, groups will distribute tasks among their members.

People also need to coordinate how skills, know-how and tools are distributed over time and space. Trading in South Mali requires bridging of long distances, adaptation to seasonality, securing finance and transport, and finding buyers. The temporal dimension of trading is visible in how traders adapt to seasonality and to how it is adjusted to people’s availability in time. Trading is also spatially situated. Poor infrastructure and long travel distances are characteristic of rural South Mali. Both the cooperative as well as the trading network therefore have a layered structure of actors close to the field, actors in the central village or market where the sesame or cereals are collected, and actors in the city to which the sesame or cereals are transported.

People do not organise in a random constellation. The range of options they can choose from are importantly influenced by the institutions active in decision-making at village level, the relationship between state and rural communities, the social networks people operate in, and the historically developed rules and regulations in market transactions. Also, previous ways of organising play a role in today’s way of organising. The empirical analyses demonstrate that organising trade is ‘path dependent’. Nevertheless, people only reproduce those procedures, habits and actions that are deemed necessary to perform. They blend old and new ways of coordination and collaboration to allow the practice of trade to continue.

The findings in this thesis show that collaboration does not rely on social relations only. Cooperating to achieve a practical end, i.e. to trade, is also skill and competence based. Organisational sustainability depends on how grouped or networked actors coordinate actions in response to changing circumstances and opportunities. Hence, organisational diversity can be understood from the fact that organisation emerges from a situated practice.


Organisation in trade emerges gradually and adaptively from what is present in terms of skills, capacities, know-how and experience in trading. As this is situation specific it is essential to recognize the uniqueness of each organisational form and suggests reconsidering the one-size-fit-all approaches often promoted in development interventions. Imposed organisational structures may be enabling to some extent but they leave little room for exploring the range of possible ways to achieve trading. For understanding how people organise trade it is important to understand the way they perform the actual practice in the specific social and material circumstances. The empirical chapters argue in favour of tutor–apprentice relations between experienced actors and new members, leaving decision-making power and rule setting in the hands of the most experienced traders. Current development projects supporting links between farmers and buyers often aim to be ‘inclusive’ and ‘pro-poor’, meaning that they should be accessible to anyone. The field research shows that organisations in trade in Mali are very selective in membership to assure the group achieves its objectives. Governments and other development actors should be aware of the trade-offs between inclusive, democratic organisational models, and effectiveness and performance in trading.

Networking, social capital and gender roles in the cotton system in Benin
Maboudou Alidou, G. - \ 2014
University. Promotor(en): Anke Niehof, co-promotor(en): Jarl Kampen. - Wageningen : Wageningen University - ISBN 9789462570634 - 187
katoen - productie - boeren - landbouwhuishoudens - boerenorganisaties - sociaal kapitaal - netwerken - geslacht (gender) - strategieën voor levensonderhoud - benin - cotton - production - farmers - agricultural households - farmers' associations - social capital - networks - gender - livelihood strategies

Cotton production in Benin, West Africa, is intertwined with colonialism, which contributed to the trans­formation of the crop’s production system from traditional to modern. Through­out the years, the importance of the crop for the stakeholders varied. The last decades have witnessed a growing interest in cotton of farmers, businessmen, and the State. From having a marginal status during the seventies and the first half of the eighties, cotton grew in importance during the nineties, both in terms of area covered and income generated, averaging 37 percent of the total cultivated area in the country. Thus, cotton has a critical cash function and plays a key role in Benin’s economic growth, accounting for an important share in the State’s revenues and farm house­holds incomes. Indeed, the share of cotton exports represented 75 percent of the country’s total agricultural exports during the 2000s, and the crop provided up to 80 percent of rural households incomes in the North. Though cotton is grown throughout the country, its production was always concentrated in the North, where it is embedded in a farming system formerly dominated by food crops. Hence, cotton transformed subsistence farming into semi-subsistence farming.

The central position of the crop in the country’s economy, which loomed large at the beginning of the 1990s, led to agricultural and economic policies being greatly influenced by the crop for decades. The Structural Adjustment Program of the early 1990s prescribed the liberalisation of the cotton sector, which had huge effects on the sector. This resulted in an increased importance of cotton farmer organisations that elapsed into the first ever hierarchical network in the country, and the crop being put at the forefront of agricultural development programs. Enduring benefits for farmers, farming communities, private actors, and the State were derived from that evolution. This gained cotton the status of ‘white gold’. The institutional dynamics that followed in the wake of liberalisation and their corollary of actors’ interactions generated never-ending conflicts of various kinds, particularly within the cotton farmers’ networks. These resulted in atomised networks. As a consequence, the benefits attached to cotton then started to wane and cotton production became a dilemma for farmers, as reflected in a steep decline of cotton production.

This thesis aims at understanding the dynamic interactions between the economic activity of cotton production and the structure of social relations from community to household and individual level. It addresses the question of how farmers’ agency affected their organisations, the cotton system, and the collective action that evolved around the crop. The research was aligned along three main axes: the emergence of breakaway networks, the decline of social cohesion and the squeeze of collective action, and the livelihoods reconstruction after the demise of cotton production. The main theoretical perspectives underlying the conceptual framework were an actor-oriented approach, actor-network theory, livelihood theory, and a gender perspective.

The research is based on fieldwork carried out in four provinces in the North of Benin from January 2009 to April 2011. Benin is a country whose employment capacity and economic growth heavily rely on the agricultural sector, in which cotton is a dominant factor. This is still the case for rural areas in the North, where rural households have been heavily dependent on cotton as a critical cash crop for poverty alleviation. Northern Benin supplies more than 75 percent of the cotton yearly produced in the country, thanks to the favourable agro-ecological conditions prevailing there, and because there is less population pressure than in the southern part. The exploratory phase of the research covered four provinces: Borgou, Alibori, Atacora and Donga. Since the provinces of Borgou and Alibori host the heart of the cotton belt, subsequent data collection progressively focussed on these two provinces.

The research adopted a mixed-methods design, applying quantitative and qualitative methods of data collection. A survey was combined with focus-group discussions, in-depth interviews and the life history method, to unveil the dynamic interactions between social actors and their interactions with the material and technical elements of the cotton system. The life history method was used to document the experience of women leaders that had made them exceptions to the rule among women cotton farmers. Apart from cotton farmers and their leaders, other targets groups of the research, like inputs suppliers and executives of cotton bodies, often had to be found beyond the two provinces in other parts of the country. The research covered eight cotton networks in ten villages in the four provinces. Survey interviews and in-depth interviews were conducted with 148 heads of cotton farming households, men as well as women.

About 80 percent of the farmers in the sample were in their 40s or 50s, and more than half of them had no formal education. Educated women represented only 17 percent of their category, suggesting that male cotton farmers are significantly more educated than their female counterparts. The average household size was 16, with about 11 workers in male adult equivalents. While agriculture is the main occupation and often the only source of income in the area, women turned out to rely less on agricultural incomes than men.

With regard to networking, the process of atomisation resulted in about 20 percent of stayers in remnant networks, 51 percent of joiners of operating networks, and about 28 percent of creators of new networks. It was found that more than three quarters of cotton farmers broke away from their original network at least once during their cotton cropping career, and that creators of new networks were more likely to be leaders than stayers or joiners. The results further tell us that more than one in two cotton farmers (ever) had a leadership position. A significant association was found between these three categories of farmers and leadership status. Finally, a greater stock of social capital was correlated with the ability of leading cotton networks.

The research indicates that the liberalisation of an agricultural value-chain can be harmful rather than beneficial when the State fails to play a coherent role during the shift from State monopoly to private interest. Cotton proved to be the lifeline for farmer organisations, and drove collective action in rural areas from the important resources it generated. However, the decline of trust within the networks in conjunction with poor management of cotton resources led to a reversed dynamic that tore networks apart, which resulted in their atomisation. Social relations deteriorated when the financial stakes became higher. As attested by the way the process of network atomisation evolved, cooperation within large groups requires legal sanctions to be sustainable. The qualitative results showed that the process of atomisation was nurtured by ties of friendship, kinship, residence and ethnicity at the start, after which networks extended to include other areas and more general member­­ship. From the survey results it can be inferred that push and pull factors interacted to influence the process of cotton network atomisation. The most influential of these factors were, on the one hand, mismanagement of network resources and manipulation of farmers by outsiders, and, on the other hand, trust in board members, hope for board positions, the expectation of profit, and support from public officials and ethnic or religious connections.

The research further demonstrates that gender myths and stereotypes obstruct women's active involvement in managing organisations, in spite of their key position in the cotton production system at household level. Women were found 21 times less likely to be a leader than men in cotton organisations, and their presence on boards hardly empowered them because they spend their energy struggling to meet practical needs. Women’s admission to cotton boards appears to be instrumental for men and hides men's real motives, judging by the way male board members tend to restrict the power of their female colleagues. However, men are inclined to give more freedom to women when they find their activities benefitting themselves, as was revealed by the data on livelihood adaptation strategies.

The research clearly ascertains that farmers are more rational than often assumed and that they grow a crop as long as it is a source of livelihood and food security. Despite its current low to negative returns, cotton remains part of the livelihood diversification strategies of households because cotton production gives access to fertilisers which can then be used for food crops. However, relying on one source of income puts the livelihood system of rural households at risk. Faced with the cotton problems, households diversified their sources of income, first and primarily on-farm with food crops increasingly gaining a cash function. Additionally, they would deploy beyond-farm alter­native strategies, including migration of youth. It was also found that the decline of cotton production proved to result in more freedom for women. Because of their multiple extra-domestic activities, women are less vulnerable than men when it comes to coping with livelihood shortages. Their contribution to the provision for house­hold needs increased during the decline of cotton production and the ensuing income shortages compared to that of men. The livelihood adaptation strategies showed the decision making about income diversification to move from the centre of the household to its periphery.

Stimuleren van Groene Groei. Verkenning van initiatieven voor circulaire en emissiearme economie
Brouwer, F.M. ; Verburg, R.W. ; Burg, S.W.K. van den - \ 2014
Den Haag : LEI Wageningen UR (Report / LEI 2014-011) - ISBN 9789086156740 - 98
economische ontwikkeling - energiebesparing - hernieuwbare energie - energiebeleid - katoen - textiel - duurzame ontwikkeling - melkveehouderij - biobased economy - overheidsbeleid - nederland - economic development - energy saving - renewable energy - energy policy - cotton - textiles - sustainable development - dairy farming - government policy - netherlands
Het Kabinet heeft in 2013 een groene groeistrategie geformuleerd. In opdracht van het ministerie van Economische Zaken (EZ) heeft het LEI een onderzoek uitgevoerd om de kansen en belemmeringen voor vergroening voor enkele voorbeelden uit te werken. De volgende drie casussen zijn uitgewerkt: energiebesparing en decentrale opwekking van hernieuwbare elektriciteit; verduurzaming van en hergebruik in de katoenketen; vergroening als voorwaarde voor groei in de zuivelsector.
Let the numbers speak : Comparing Better Cotton Fast Track Program participants and non-participants in India, Mali, and Pakistan using agronomic data of the Better Cotton Initiative
Ge, L. ; Waarts, Y.R. - \ 2014
The Hague : LEI Wageningen UR (LEI report 2013-067) - ISBN 9789086156672 - 82
katoen - katoenindustrie - duurzame landbouw - duurzaam bodemgebruik - milieu - arbeid (werk) - watergebruik - pesticiden - landbouwproductie - india - mali - pakistan - cotton - cotton industry - sustainable agriculture - sustainable land use - environment - labour - water use - pesticides - agricultural production
Cotton in Benin: governance and pest management
Togbe, C.E. - \ 2013
University. Promotor(en): Arnold van Huis; D.K. Kossou; S.D. Vodouhe, co-promotor(en): Rein Haagsma. - Wageningen : Wageningen UR - ISBN 9789461738073 - 201
gossypium hirsutum - katoen - plagen - gewasproductie - gewasbescherming - biologische bestrijding - neemextracten - beauveria bassiana - bacillus thuringiensis - veldproeven - participatie - boeren - plagenbestrijding - plagenbehandeling - geïntegreerde plagenbestrijding - benin - cotton - pests - crop production - plant protection - biological control - neem extracts - field tests - participation - farmers - pest control - pest management - integrated pest management

Key words: cotton, synthetic pesticides, neem oil (Azadirachta indica), Beauveria bassiana,

Bacillus thuringiensis, field experiment, farmers’ participation

Pests are one of the main factors limiting cotton production worldwide. Most of the pest

control strategies in cotton production rely heavily on the application of synthetic pesticides.

The recurrent use of synthetic pesticides has large consequences for the environment (air,

water, fauna, and flora) and human health. In cotton growing areas in Benin, targeted pests

develop resistance, and this resistance is extended to malaria mosquitos. Other negative

impacts are pest resurgence and secondary pest outbreaks due to the effects on the beneficial

insect fauna. This dissertation addresses the technical and institutional constraints hindering

the wide-scale use of staggered targeted control, ‘Lutte étagée ciblée’ (LEC, in French) for

cotton production.

Wider adoption of LEC can only be achieved if some institutional changes were to

occur, such as in the role of input suppliers in order to improve the procurement of LEC

pesticides. This can only happen if farmers would be empowered and better organised.

Locally available phytochemicals and biopesticides can be used to address problems related to

the difficulty in obtaining synthetic pesticides, as well as their negative environmental impact.

Neem oil (Azadirachta indica) and Beauveria bassiana are good candidates to be used in an

integrated pest management approach, as their impact on the beneficial fauna is minimal. We

tested whether the efficacy could be enhanced by using mixed formulations of neem oil and

bio-insecticides, but yields obtained with neem oil used alone and mixed with biopesticides

were not different. This suggests an absence of a synergistic effect between neem oil and B.

bassiana (Bb11) and between neem oil and B. thuringiensis. The combination of biopesticides

increased the cost of production more than that of the conventional treatments, compromising

the profitability of such formulations. Participation in the research process increased farmers’

knowledge on pest and natural enemy recognition. The increase in knowledge did not lead to

any modification in farmer practices with respect to the use of neem oil and Beauveria, but it

led to a significant change towards threshold-based pesticide applications. Policy implications

for successfully changing farming practices are discussed.

Economic and environmental analysis of energy efficiency measures in agriculture, Case Studies and trade offs
Visser, C.L.M. de; Voort, M.P.J. van der; Stanghellini, C. ; Ellen, H.H. ; Klop, A. ; Wemmenhove, H. - \ 2013
agrEE - 157
landbouw - landbouw en milieu - energie - energiegebruik - efficiëntie - akkerbouw - gewasproductie - tarwe - aardappelen - katoen - rotaties - bedrijfssystemen - melkveehouderijsystemen - melkveehouderij - rundvleesproductie - pluimveehouderij - vleeskuikens - varkenshouderij - europa - glastuinbouw - agriculture - agriculture and environment - energy - energy consumption - efficiency - arable farming - crop production - wheat - potatoes - cotton - rotations - farming systems - dairy farming systems - dairy farming - beef production - poultry farming - broilers - pig farming - europe - greenhouse horticulture
This report illustrates case studies with an in-depth analysis of the interactions of energy efficiency measures with farm economics and the environmental impact (GHG) of the measures across Europe. The analyses followed a common methodology considering the farm gate as the system boundary. Therefore, considerable energy use in the post-processing of agricultural products were only taken into account, when they can be assumed to be realized on the farm. The analyses of the energy use, economic and environmental effects follow an LCA approach taking into account all costs of the production, including those for machines according to the concept of “useful life” of the machines used. The environmental effects of energy saving were illustrated with the greenhouse gas emission effect of the energy efficiency measures. The case studies are only a selection of specific energy saving measures across Europe and therefore cannot be regarded as representative for all Europe. Nevertheless, they will help to understand constraints and opportunities for increased energy efficiency in agriculture, which can be used to translate to an agenda of practical action or applied research. The findings are valid sometimes only in the specific regional settings, sometimes they are of general validity.
Insecten te lijf met ingebouwde sluipmoordenaar. Een plant die zijn plaaginsect al bij het eerste hapje doodt: een Bt-gewas heeft er geen insecticide voor nodig. Is het de ultieme plaagbestrijder of een biologisch gevaar? (interview met C.C.M. van de Wiel)
Scharroo, J. ; Wiel, C.C.M. van de - \ 2012
Bionieuws 22 (2012)18. - ISSN 0924-7734 - p. 8 - 9.
insectenplagen - maïs - genetische modificatie - transgene planten - katoen - akkerbouw - gewasbescherming - insect pests - maize - genetic engineering - transgenic plants - cotton - arable farming - plant protection
Een plant die zijn plaaginsect al bij het eerste hapje doodt: een Bt gewas heeft er geen insecticide voor nodig. Is het de ultieme plaagbestrijder of een biologisch gevaar? Bt staat voor Bacillus thuringiensis, een algemeen voorkomende grampositieve bodembacterie. Die produceert kristaleiwitten die giftig zijn voor insecten uit verschillende ordes en voor nematoden. In de jaren tachtig besloten wetenschappers planten zelf deze toxinen te laten produceren. Het Vlaamse biotechbedrijf Plant Genetic Systems was in 1985 de eerste die met een met B-genen uitgerust gewas op de markt kwam
Agricultural intensification : saving space for wildlife?
Baudron, F. - \ 2011
University. Promotor(en): Ken Giller, co-promotor(en): M. Corbeels; Jens Andersson; Pablo Tittonell. - [S.l.] : S.n. - ISBN 9789085859642 - 244
semi-aride klimaatzones - beschermingsgebieden - intensivering - kleine landbouwbedrijven - boeren - wild - hulpbronnenbeheer - katoen - natuurbescherming - zimbabwe - semiarid zones - conservation areas - intensification - small farms - farmers - wildlife - resource management - cotton - nature conservation

Key words: agricultural frontier; smallholder; intensification; semi-arid area; wildlife; conservation agriculture; cotton; Zimbabwe.

Increasing agricultural production and preventing further losses in biodiversity are both legitimate objectives, but they compete strongly in the developing world. In this study, current tensions between agricultural production and environmental conservation were described and analysed in Mbire District, an agricultural frontier shared with wildlife that lies in the Mid-Zambezi Valley, in the northern fringe of Zimbabwe. The potential of conservation agriculture (CA) to intensify agricultural production with minimum negative environmental effects was then explored. The population of Mbire District almost doubled between 1992 and 2002, while the livestock densities increased at rates above 15% in the early 1990s and the late 2000s. From 1980 to 2007, the expansion of farmland over the years was described by an exponential relationship. It was suggested that these changes affected elephant and buffalo numbers negatively. Increase in human population, increase in cattle population, and expansion of cotton farming were all drivers on the observed land use change. However, cotton farming was demonstrated to be paramount, enabling cattle accumulation and expansion of plough-based agriculture. The ‘environmental footprint’ per farm was increasing significantly with the area under cotton and with the number of draught animals owned. A kilogram of seed cotton required 50% more land, removed twice as much N, 50% more K and 20% more P than a kilogram of cereal. However, except for pesticide, one man-day invested in cotton production had a smaller environmental footprint than a man-day invested in cereal production. As farming in Mbire District is limited by labour more than by land, specialising in cereal production would increase the total area occupied by crops and fallows, whilst specializing in cotton production would reduce this area. Therefore, maintaining or increasing the relative profitability of cotton vs. cereal may ‘spare land’ for nature. Compared with current farmers’ cropping practices (CP), CA had no effect on cotton productivity during years that received average or above average rainfall. During a drier year, however, CA was found to have a slightly negative effect (110 kg ha-1 less in on-farm trials and 220 kg ha-1 less in farmers’ cotton fields). Most soils in the study area are coarse-textured soils, on which runoff were significantly greater with CA than with CP. For these reasons, farmers perceived ploughing as necessary during drier years to maximize water infiltration, but saw CA as beneficial during wetter years as a means to ‘shed water’ and avoid waterlogging. In Zimbabwe, the approach used in the extension of CA appears to differ little from an earlier attempt to intensify smallholder agricultural production almost a century earlier: the Alvord model. In particular, the rationale of African smallholder farming has been persistently ignored. The analysis of smallholder farming practices in Mbire District showed how the socio-economic constraints they faced predisposed them towards extensification. In particular, labour availability for weeding was found to be a major limiting factor in the area. The increased weed pressure in CA is therefore a major reason preventing smallholders from embracing it. As a conclusion, mitigating conflicts between agricultural production and biodiversity conservation will require major innovations, far beyond CA. CA should be seen as part of a larger basket of technologies aiming at ‘ecological intensification’. In parallel to the development of technical innovations, local institutions should be empowered and strong regulations put in place.

Duurzaamheid van de huidige genetisch gemodificeerde gewassen : effecten van de teelt van genetisch gemodificeerde soja, maïs en katoen op People, Planet en Profit (mens, milieu en economie)
Lotz, L.A.P. ; Breukers, M.L.H. ; Broer, W. ; Bunte, F. ; Dolstra, O. ; Engelbronner-Kolff, F.M. d'; Franke, A.C. ; Montfort, J. ; Nikoloyuk, J. ; Rutten, M.M. ; Smulders, M.J.M. ; Wiel, C.C.M. van de; Zijl, M. van - \ 2011
Wageningen : Plant Research International - 24
gewassen - duurzaamheid (sustainability) - genetisch gemanipuleerde organismen - glycine max - maïs - katoen - koolzaad - zea mays - gossypium hirsutum - brassica napus var. oleifera - transgene planten - crops - sustainability - genetically engineered organisms - maize - cotton - rape - transgenic plants
Deze studie richt zich op genetische modificatie bij gewassen. Wereldwijd werden in 2010 op meer dan 140 miljoen hectare GG-gewassen verbouwd. Dit is ongeveer 70 maal het totale Nederlandse landbouwareaal. Het gaat met name om de handelsgewassen soja, maïs, katoen en koolzaad. Twee GG gewassen zijn ondertussern in de EU toegelaten voor teelt, namelijk maïs dat resistent is tegen bepaalde insecten en een aardappel met een verhoogd zetmeel gehalte.
Sustainability of current GM crop cultivation : Review of people, planet, profit effects of agricultural production of GM crops, based on the cases of soybean, maize, and cotton
Franke, A.C. ; Breukers, M.L.H. ; Broer, W. ; Bunte, F.H.J. ; Dolstra, O. ; Engelbronner-Kolff, F.M. d'; Lotz, L.A.P. ; Montfort, J. ; Nikoloyuk, J. ; Rutten, M.M. ; Smulders, M.J.M. ; Wiel, C.C.M. van de; Zijl, M. - \ 2011
Wageningen : Plant Research International (Report / Plant Research International 386)
transgene planten - gewassen - duurzaamheid (sustainability) - glycine max - sojabonen - zea mays - maïs - gossypium hirsutum - katoen - risicoschatting - akkerbouw - transgenic plants - crops - sustainability - soyabeans - maize - cotton - risk assessment - arable farming
This report adresses the question whether the cultivation of genetically modified (GM) crops abroad for import in the Netherlands, as compared to the cultivation of their conventional (non-GM) counterparts, is in line with Dutch policy and societal aims striving after more sustainable forms of agriculture worldwide and the utilization of the benefits offered by biotechnology in a responsible manner. Three crops were selected as case study objects: sybean, maize and cotton. The sustainability of GM and non-GM crop production was compared with each other based on a review of scientific and other literature. This comparison followed characteristics and criteria associated with the sustainability concept of 'people, planet, profit'.
Welke effecten hebben genetisch gemodificeerde gewassen op bestrijdingsmiddelengebruik? : KNPV-najaarsvergadering GMO en Gewasbescherming: waar trekken we de grens?
Kleter, G.A. - \ 2008
Gewasbescherming 39 (2008)2. - ISSN 0166-6495 - p. 71 - 72.
gewassen - sojaproducten - maïs - katoen - genetische modificatie - transgenen - diervoedering - gewasbescherming - akkerbouw - crops - soyabean products - maize - cotton - genetic engineering - transgenics - animal feeding - plant protection - arable farming
Gijs Kleter (RIKILT) ging in op het effect van GG-gewassen op de gemeten en op basis van scenario-studies voorspelde vermindering van het gebruik van gewasbeschermingsmiddelen en daarmee de afname van de milieubelasting (verschuiving in gebruikte middelen en lagere doseringen). In herbicidentolerante GG-gewassen is onkruidbestrijding eenvoudiger maar kan ook sneller leiden tot resistentie-ontwikkeling
Facilitating learning toward sustainable cotton pest management in Benin : the interactive design of research for development
Sinzogan, A.A.C. - \ 2006
University. Promotor(en): Arnold van Huis; D.K. Kossou; J.L.S. Jiggins; V. Agbo. - [S.l.] : S.n. - ISBN 9085044324 - 185
katoen - katoenindustrie - plantenplagen - duurzaamheid (sustainability) - onderzoek - gossypium hirsutum - insectenplagen - geïntegreerde plagenbestrijding - plantaardige insecticiden - bacteriële insecticiden - informatieverspreiding - leren - benin - landbouwvoorlichting - cotton - cotton industry - insect pests - plant pests - integrated pest management - bacterial insecticides - botanical insecticides - sustainability - research - diffusion of information - learning - agricultural extension
Impact of integrated pest management farmer field schools on health, farming systems, the environment, and livelihoods of cotton growers in Southern India
Mancini, F. - \ 2006
University. Promotor(en): Ariena van Bruggen, co-promotor(en): J.L.S. Jiggins; Aad Termorshuizen. - Wageningen : s.n. - ISBN 9085043883 - 112
geïntegreerde plagenbestrijding - gossypium - katoen - boeren - gezondheid - pesticiden - bedrijfssystemen - milieueffect - impact - levensomstandigheden - india - welzijn - integrated pest management - cotton - farmers - health - pesticides - farming systems - environmental impact - living conditions - well-being - cum laude
cum laude graduation (with distinction)
The sustainability of cotton : consequences for man and environment
Kooistra, K.J. ; Termorshuizen, A.J. ; Pyburn, R. - \ 2006
Wageningen : Science Shop Wageningen UR (Report / Wetenschapswinkel Wageningen UR 223) - ISBN 9085850002 - 60
biologische landbouw - geïntegreerde plagenbestrijding - katoenindustrie - katoen - duurzaamheid (sustainability) - certificering - kwaliteitscontroles - agro-industriële ketens - organic farming - integrated pest management - cotton industry - cotton - sustainability - certification - quality controls - agro-industrial chains
This project aimed to summarise literature that compares conventional, IPM, and organic cotton production systems in terms of environmental impact; to select indicators which can be used to compare the environmental impact of conventional, IPM, and organic cotton production systems and to start a discussion on the social aspects relevant for trade in sustainable cotton.
Cotton-Made in Africa : Quantifying the Sustainability of Cotton Production
Bos, M.G. ; Bosch, R. van den; Diemont, H. ; Keulen, H. van; Lahr, J. ; Meijerink, G. ; Verhagen, A. - \ 2005
Wageningen : Alterra - 47
katoen - gewasproductie - afrika - duurzaamheid (sustainability) - water - voedingsstoffen - plagenbestrijding - milieu - inkomen van landbouwers - marketing - cotton - crop production - africa - sustainability - nutrients - pest control - environment - farmers' income
Behaviour of wild-type and genetically modified baculoviruses in the Helicoverpa armigera - cotton system: a simulation approach
Sun, X. - \ 2005
University. Promotor(en): Just Vlak, co-promotor(en): Wopke van der Werf. - Wageningen : - ISBN 9085041678 - 172
baculovirus - gossypium hirsutum - katoen - helicoverpa armigera - insectenplagen - genetische modificatie - transmissie - biologische bestrijding - modellen - virale insecticiden - cotton - insect pests - genetic engineering - transmission - biological control - models - viral insecticides
De vruchten van genetische modificatie
Zadoks, J.C. - \ 2002
Gewasbescherming 33 (2002)4. - ISSN 0166-6495 - p. 135 - 135.
plantenziektekunde - genetische modificatie - economie - ziekteresistentie - plaagresistentie - katoen - sojabonen - plant pathology - genetic engineering - cotton - soyabeans - disease resistance - pest resistance - economics
Kritische beschouwing over de economische voordelen van genetische modificatie met betrekking tot de gewasbescherming in katoen en soya
Coping behaviour of extension agents in role conflict situations : a case study in Xinji county, China
Huang, R.Q. - \ 1998
Agricultural University. Promotor(en): Cees van Woerkum; M.C.H. Wagemans. - S.l. : Huang - 160
plattelandsontwikkeling - plattelandsplanning - landbouw - katoen - economische situatie - innovaties - modernisering - rolconflicten - gedrag - china - landbouwvoorlichting - economische productie - rural development - rural planning - agriculture - cotton - economic situation - innovations - modernization - role conflicts - behaviour - agricultural extension - economic production
<p>This book is about the coping behaviour of extension agents in role conflict situations in a changing environment in China. The study presents the case of cotton production in Xinji county, China.</p><p>Chapter 1 gives background information on Chinese agricultural and rural reform since 1978 and its impact for extension system and extension agents. Before the rural reform, Chinese agriculture was collectively managed. The extension system dealt with collective groups of farmers and was used as a policy instrument to implement government policy. Since the rural reform, the rural economy and social environment have been changed considerably, the main transformations being that the managerial unit changed from commune and brigade to individual household, and traditional agriculture switched to industrialised and commercialised agriculture. After the rural reform, the extension system had to deal with individual farmers and to take their wishes into consideration.</p><p>The second Chapter formulates the research problem and research objectives. Since the reform, it has become clear that farmers' interests also have to be served by the extension system. Farmers will not follow extension recommendations unless they are convinced that it is in their interests to do so. Thus the client market has emerged alongside policy as a second important driving force for the extension system. Now the extension system has to serve both the interests of policy makers and farmers. In China there is a clear conflict between the goals of the government and of farmers in the field of cotton production. The government wants farmers to produce a certain amount of cotton while farmers want to make more profits from non-farming sectors or in growing fruit trees and vegetables. Therefore, two driving forces - policy and client market - create a conflict situation for the extension agents. The extension agents find themselves exposed to conflicting expectations. From this, the main research question emerges as: how do extension agents in Xinji county experience and cope with the role conflict generated by the increasingly opposing demands of the policy mandate and client market force? Research objectives and relevance of the study are also discussed in this Chapter.</p><p>Chapter 3 provides a theoretical framework relevant to this study. Role conflict theories have been reviewed. As a result, four types of behaviour and three behaviour determinants are put forward. The four types of behaviour are: take sides, compromise, avoid and resolve conflict. The three behaviour determinants are: legitimate power and positive and negative sanctions power of the role senders. Some critiques on the existing role conflict theories are discussed and modifications are made, for example, a focal person's own goal is added as one behaviour determinant. Some cultural differences are also discussed in relation to the validation of the role conflict theory.</p><p>Chapter 4 presents the research approach and methodology used in this work. A grounded theory was used to guide the study process, and case studies were used to conduct the research. Data collection methods and techniques are discussed and, the Chapter concludes with some experiences of undertaking social research in China.</p><p>In Chapter 5, a description of the study area and the situation of cotton production are provided, in which the natural environment, social structure, basic facts and production with particular regard to the cotton production are elaborated. The importance of cotton production in China is also given in order to clarify why the government is intervening so strongly in this sector.</p><p>In Chapter 6, both government policy and farmers' attitudes towards cotton production are presented. Conflicts between the expectations of the government and farmers for extension agents are discussed.</p><p>The main research findings are presented in Chapters 7 and 8. All extension agents perceive a role conflict in cotton production, but the degree of role conflict varies. The higher level of extension agents (CEAs) perceive a clear role conflict, but not as strong as the extension agents at lower levels (TEAs and VLs). This study shows that the existing role conflict resolution theories are too simple and too static. It finds that there are more types of coping behaviour and more factors which determine coping behaviour. In Tables 7.2, 9.1 and 9.2, the various types of coping behaviour adopted by the different levels of extension agents are given. The reasons and conditions for adoption are also provided in these tables.</p><p>A new theoretical model for understanding the coping behaviour of extension agents is introduced in Chapter 8, in which a division is made between internal and external factors. The internal factors are considered to be the major determinants for explaining coping behaviour in a role conflict situation. They are as follows: goals of a focal person; degree of power held by a focal person; perceived legitimate power and perceived sanction power of role senders; past experience; attributes of role conflict and; interpersonal relations. The external factors do not have a direct influence on the coping behaviour of a focal person, but can influence internal factors and finally can have an indirect influence. They are: incentive structure; organisational hierarchy; focal person's background; professional position and specialisation of the focal person; whether party member; age of the focal person and; peer behaviour. The reasons behind the different types of coping behaviour of extension agents at different levels are also presented in Chapter 7. These reasons are discussed along the following lines of differentiation: the power of the focal person; the governing principles; uncertainty at varying levels; incentive structure and; feasibility of monitoring field activities and in power distance.</p><p>The handling of role conflict is a dynamic rather than a static process. Three aspects of the dynamic process are discussed in Chapter 8:<OL><LI>many roles are negotiated at all levels, and all parties within the role negotiation are both sending and receiving roles. A lot of bargaining take place in the negotiation process;<LI>there is no fixed coping behaviour in the role conflict situation, and shifting patterns of selective coping behaviour result, in line with situational changes;<LI>the relationship between all three parties (government officials, extension agents and farmers) is in a dynamic process of change. All parties experiment during the whole process of the role conflict in order to find a suitable way to deal with it.</OL></p><p>In the final Chapter, conclusions, discussion and recommendations are outlined based on the study. It is concluded that there are indeed more types of coping behaviour than the existing role conflict theory proposes. Besides taking sides, compromising, avoiding and resolving conflict, there are also other types of behaviour such as: to concentrate on one's own goal, to wait-and-see, to experiment and resign. These new types of coping greatly extend our understanding on the coping strategies that a focal person may take. This study shows that focal persons such as extension agents at any level also have some personal goals other than the expectations of the government and farmers. These personal goals influence their coping behaviour to a certain extent. The only point of differentiation might be the degree of power that the focal persons have in seeking their own goals in a role conflict situation. As this study shows, CEAs have more power to pursue their own goals than TEAs and VLs. When faced with a role conflict situation, extension agents demonstrate a more professional attitude at county level, but act more as government officials at township level. In a difficult role conflict situation, focal persons do not always take action. They may wait-and-see or even resign from the conflict situation. These two strategies are normally applied when role senders from different sides put strong pressure on the focal persons, leading to them not knowing how to perform their tasks. The identification of the strategy of experimentation is extremely important in extending our understanding of the focal person's coping behaviour. This study shows that a focal person would adopt this behaviour in a new and difficult situation.</p><p>This research indicates that the strength of a role conflict is a very important determinant for understanding the coping behaviour of focal persons. When the role conflict is weak, i.e. when the difference in expectations between role senders is not big, then it is fairly straightforward for a focal person to respond in certain ways. In this case decisions will be strongly related to the focal person's own goals or other factors, because no matter what he/she does, there will be no strong objections from either of the role senders. However, when the role conflict becomes strong, i.e. when the difference in expectations between role senders is big, then a focal person may find it difficult to commit him/herself to certain behaviour, especially when both role senders have sanction powers. In such cases, the focal persons are more likely to become ego defensive and fall back onto other coping strategies, such as wait-and-see or experimentation. This factor has received little attention in the existing role conflict theory. In the final section of Chapter 9, some areas for further research and practical recommendations are suggested, based on the research results.</p>
Biological control of cotton aphid (Aphis gossypii Glover) in cotton (inter)cropping systems in China : a simulation study
Xia, J. - \ 1997
Agricultural University. Promotor(en): R. Rabbinge, co-promotor(en): Wopke van der Werf. - S.l. : Xia - ISBN 9789054857136 - 173
biologische bestrijding - insecten - nuttige insecten - katoen - Aphididae - Coccinellidae - gemengde teelt - tussenteelt - meervoudige teelt - tussenplanting - computersimulatie - simulatie - simulatiemodellen - China - Aphis gossypii - Coccinella septempunctata - biological control - insects - beneficial insects - cotton - mixed cropping - intercropping - multiple cropping - interplanting - computer simulation - simulation - simulation models
<p>Cotton aphid ( <em>Aphis gossypii</em> Glover) is the key insect pest of seedling cotton ( <em>Gossypium hirsutum L.</em> ) in China, particularly in the North China cotton region. The resulting annual losses amount to 10-15% of the attainable yield. Sole reliance on insecticides against the cotton aphid in the past four decades has brought about a rapid development of insecticide resistance, serious outbreaks of key pests, resurgence of secondary pests, and risk for man and environment. Biological control of the cotton aphid by naturally-occurring seven-spot beetle ( <em>Coccinella septempunctata L</em> .) is the first priority for integrated pest management in cotton to avoid early season application of insecticides and lay a foundation for biological control of aphids and other pests during the season. Augmentation of the seven-spot beetle by intercropping cotton with wheat is the most commonly used approach for cotton aphid biological control. Disadvantages of intercropping are decreased fiber and seed quality, increased outbreaks of cotton bollworm ( <em>Helicoverpa armigera</em> Hubner) and verticillium wilt ( <em>Verticillium dahliae</em> Kleb.), and difficulties with mechanization. There is, therefore, a demand for developing more sociologically, economically and ecologically sound cotton-wheat intercropping systems. Systems research provides an appropriate framework to analyse biological control systems and prototype promising biological control strategies. The objective of this study is (1) to better understand and quantify the major processes in <em>C. septempunctata-A. gossypii</em> system in cotton monoculture and cotton-wheat intercrop; (2) to develop simulation models of the dynamics of the coccinellid- aphid system in both cotton cropping systems by integrating process-level knowledge; and (3) to use the models to obtain insight in the dynamic behavior of the system and explore intercropping strategies that are not only favorable for biological control but also advantageous with respect to labor requirement, fiber and seed quality, and suppression of the cotton bollworm and verticillium wilt by cultural practices.<p>A major factor affecting <em>A. gossypii</em> population growth is temperature. Life table parameters of the cotton aphid were determined at 10, 15, 20, 25, 30 and 35 ± 0.5°C in the laboratory (Chapter 2). The relationship of temperature with the developmental rate of each life stage (the reciprocal of the stage duration) was described using Logan curves. The relationship of temperature with the relative mortality rate of each prereproductive stage and each adult age class was described using parabolas. The relationship of temperature with the mean reproductive rate of each adult age class was described using the Weibull model. Development of <em>A. gossypii</em> was fastest at 30°C, with a pre-reproductive period of 4.6 d. The greatest survival from birth to adult (81 %) was obtained at 25°C. Fecundity was maximum at 25°C , with a total fecundity of 28.3 nymphs per female and a mean reproductive rate of 3.1 nymphs per female per day. Threshold temperatures for development of the first to fourth instar and the adult were 8.2, 8.0, 7.2, 6.2 and 7.9°C, respectively; and the thermal constants were 24.2, 23.7, 23.0, 25.5 and 168.8 degree-days (D°), respectively. <em>A. gossypii</em> obtained its greatest intrinsic rate of increase (0.386 d <sup>-1</SUP>) at 25°C. High relative rate of population increase at 25°C resulted in a daily population increase of 47% and a doubling time of 1.8 d, illustrating the tremendous growth capacity of <em>A. gossypii</em> under favorable conditions. Comparison to similar records from other crops indicates a relatively high heat tolerance of <em>A. gossypii</em> on cotton in North China. The data gathered are used to construct a simulation model of <em>A. gossypii</em> population dynamics in cotton.<p>Temperature and food quantity are two major factors affecting C. <em>septempunctata</em> population growth. Life history parameters of the seven-spot beetle feeding on <em>A. gossypii</em> were determined in two experiments in the laboratory (Chapter 3). The first experiment addressed the effect of five temperatures (15, 20, 25, 30 and 35 ± 0.5°C) on the beetle bionomics, while the second one addressed the effect of food quantity on the beetle bionomics at a temperature of 25°C. The relationship between temperature and the developmental rate of each life stage was described with Logan curves. The relationship of temperature with the relative mortality rate of each pre-oviposition stage and each adult age class was described with parabolas. The relationship between temperature and the mean oviposition rate of each adult age class was described with the Weibull model. <em>C.</em><em>septempunctata</em> developed most rapidly at 35°C, with a preimaginal period of 10.8 d. The highest survival from egg to adult (47%) was obtained at 25°C. Oviposition was greatest at 25°C, with a total oviposition of 287.4 eggs per female and a mean oviposition rate of 22.4 eggs per female per day. Threshold temperatures for development of eggs, larvae, pupae and adults ranged from 10.9 to 13.9°C, with 12.6°C for the entire life span; and thermal constants were 42.0, 103.7, 63.6 and 302.9 D°, respectively. Over the range of prey densities tested, a 3.54-fold increase in prey density resulted in a 2-fold reduction in larval development time and a 3-fold increase in larval survival. A 2-fold increase in prey density led to a 2-fold increase in total oviposition and the mean oviposition rate. The data gathered are used to construct a simulation model of <em>C.</em><em>septempunctata</em> population dynamics in cotton.<p>Functional responses of five foraging stages of <em>C. septempunctata</em> on three sizegroups of <em>A. gossypii</em> (mixed first and second nymphs, mixed third and fourth nymphs, and adults) at five temperatures (15, 20, 25, 30 and 35 ± 0.5°C) were determined in the laboratory (Chapter 4). All functional responses were of type 11 and were adequately described by Rogers' random predator equation. The search rate increased linearly from 15 to 35°C with a factor of 3-8. The handling rate showed a curvilinear relation to temperature and was lowest at 15°C. There was a considerable variation in the latter response curves in different predator-prey stage combinations. In some predator-size- groupsprey interactions, handling rate increased consistently with temperature, while in other combinations, the relationship had a maximum at an intermediate temperature. Search rate increased with 50-100% from one larval predator instar to the next but decreased from the fourth instar to the adult predator. There was only moderate difference in search rate between prey size-groups for the same predator stage (&lt; 50% between extremes). Handling rate increased with 50-100% from one predator stage to the next, but it was somewhat similar in the fourth instar and adult predators. Handling rate towards early instar, late instar and adult prey varied with a ratio of about 3:2:1. The functional responses are incorporated in the simulation model of <em>C.</em><em>septempunctata-A. gossypii</em> population interaction and dynamics in cotton.<p>In Chapter 5, a simulation model of the temporal dynamics of the coccinellid-aphid system in cotton monoculture was developed by integrating process-level knowledge. Six submodels were distinguished: cotton aphid, seven-spot beetle, predator-prey interaction, parasitism, cotton plant, and abiotic factors. The model was tested and evaluated at three levels of the system complexity: laboratory, field cage and open field. At each level of complexity, processes were added to the model, based on discrepancies between "original model" behaviors and observations, and additional experimentation. Processes included in the model at the laboratory level were temperature-dependent development, survival and reproduction of both insects; and prey density, prey size-group and temperature- dependent predation. Adaptations for the field cage level were density dependence of wing induction and reproduction of <em>A</em> . <em>gossypii,</em> extrapolation of the functional response from single stage interaction in experimental arenas in the laboratory to multiple stage interactions on plants, and a higher mortality for <em>C</em> . <em>septempunctata</em> than observed in the laboratory. Adaptations for the open field level were immigration rates of both insects; time- dependent parasitization of alate immigrants by <em>Allothrombium,</em> apterous aphids by hymenopterous parasitoids and seven-spot beetle pupae by <em>Tetrastichus coccinellae</em> Kurjumov; prey density-dependent departure rate of seven-spot beetle adults; prey density and prey size-group dependent predation by <em>Propylaea japonica</em> (Thungberg); and accumulated (D°)-driven cotton canopy growth. The simulated and observed data were in reasonable agreement at all levels, though discrepancies increased with the level of scale. Simulations at the open field level show that <em>C. septempunctata</em> plays a key role in controlling <em>A.</em> gossypii in cotton monoculture, but its numbers increase too late to guarantee a sufficient biological control. Predation by <em>P</em> . <em>japonica</em> and parasitism by <em>Allothrombium</em> and hymenopterous parasitoids play only a minor role. Variations in temperature or immigration of alate <em>A.</em> gossypii alone can not explain between-season differences in aphid population dynamics. Immigrating numbers of seven- spot beetle adults is the key factor.<p>Based on the model of Chapter 5, a simulation model of the spatio-temporal dynamics of the coccinellid-aphid system in cotton-wheat intercropping was developed in Chapter 6. Six submodels were distinguished: temporal dynamics of <em>A. gossypii</em> populations, temporal dynamics of <em>C.</em><em>septempunctata</em> populations on wheat, seven-spot beetle dispersal from wheat into cotton, predator-prey interaction on cotton, cotton plant, and abiotic factors. In addition to the processes common in cotton monoculture and cotton-wheat intercrop, processes related to the cotton-wheat intercrop were experimentally characterized and included: (a) immigration of alate aphids into intercropped cotton and seven-spot beetle adults into intercropped wheat; (b) prey density-dependent emigration of seven-spot beetle adults from ripening wheat by flight; (c) prey density-dependent dispersal of foraging predators from wheat into cotton by walking; (d) time-dependent parasitization in apterous aphids and seven-spot beetle pupae; and (e) accumulated (D°)-driven cotton canopy growth. Dispersal of foraging seven-spot beetles from wheat into cotton was modelled as a diffusion process. There was satisfactory correspondence between the simulated and observed data. Simulations show that the low abundance of the cotton aphid in the current cotton-wheat intercropping system is due to a combined effect of increased predation and parasitism, and decreased aphid immigration, of which predation by the seven-spot beetle is the most important. Current cotton-wheat intercropping has an "overcapacity" for biological control. Simulations indicate that effective biological control can still be achieved when the immigration rate of alate aphids is increased by a factor 4, and the proportion of the seven-spot beetle foraging on cotton and the parasitization of apterous aphid are decreased by 40%. These results suggest that it is possible to increase distance from wheat to cotton strips in the current intercropping system and maintain effective biological control of the cotton aphid.<p>Based on models developed and insights gained in this study, a promising strategy of cotton-wheat strip cropping was proposed, which would be not only favorable for <em>A. gossypii</em> biological control but also advantageous with respect to labor requirement, fiber and seed quality, and suppression of the cotton bollworm and verticillium wilt by cultural practices. For its validation, field work is required. More research is needed to determine the effect of distance from wheat to cotton strips on immigration of alate aphids into cotton and dispersal of major predators from wheat into cotton. With these parameters included in the model of Chapter 6, the promising strategy of cotton-wheat strip cropping can be identified and tested on a large scale. Observations should be also made for effectiveness and profitability of the proposed strategy for further improvement and development of cotton cropping systems in North China.
Check title to add to marked list
<< previous | next >>

Show 20 50 100 records per page

Please log in to use this service. Login as Wageningen University & Research user or guest user in upper right hand corner of this page.