index of contents

INDEX OF CONTENTS PRESENTACIÓ …………………………………………………………………… 1 AGRAÏMENTS ……………………………………………………………………. 4 SUMMARY ………………….……………………………………………………. 6 SUMARIO …………………………..………………………..………………...…. 8 RESUM ……………………………….……………………………………………. 10 SCOPE OF THE STUDY …………………………………………………………. Setting the scene ……………………………………………………..………. The weed study case ……………….……………………..…...……………... Knowledge on Papaver rhoeas ………………………..…….……………. Biology ………………………………………………………………... Control techniques ……………………………….…………………… Cultural practices ……………………………………………………... Integrated Weed Management (IWM) ………………………………... Modelling ……………………………..……………………………………… Economics ………………………….…………………….…………………... OBJECTIVES ……………………………………………………..………………. EXPERIMENTAL PROTOCOL ……………….…………..…………………… Field trial experiments ….…………………….………………….…………. Laboratory experiments ………………………………………………….…. REFERENCES …………………………………………………………………….

12 12 12 13 13 14 15 16 16 17 18 19 19 21 22

CHAPTER 1 Changes on the demography of Papaver rhoeas L. in function of cohorts emergence …….………………………………….…. 28 Abstract ………………………………………..…………………………….. Introduction …………………………………………………………….…… Materials and methods ……………………………………………………... The field site ……………………………………………………………… Life-cycle experiments …………………………………………………… Seedling emergence and survivorship ………………………………… Plant growth and biomass allocation …………………..……………. Plant reproduction …………………………………………………… Dormancy assays …………………………………………………………. Statistical analysis ………………………………………………………… Results ………………………………………………………………………...

29 30 32 32 32 33 33 34 34 35 36

Climatic data for Cubells ……………………………………..………….. Climatic data for Lleida ……………………….………………………….. Life-cycle experiments …………………………………………………… Seedling emergence …………………………………………………… Seedling mortality …………………………………………………….. Biomass allocation …………………..……………………………….. Plant reproduction ……………………………………………………. Dormancy assays ………..………………………………………………… Discussion ……………………………………………………………………. References …………………………………………………………………….

36 37 37 37 38 40 44 46 49 53

CHAPTER 2 Herbicide resistant Papaver rhoeas L. control in winter cereal with postemergence and preemergence herbicides ….. 58 Abstract ………………………………………..…………………………….. Introduction …………………………………………………………….…… Materials and methods ……………………………………………………... Results and discussion ……………………………………………………… References …………………………………………………………………….

59 60 61 65 71

CHAPTER 3 Modeling the population dynamics of Papaver rhoeas L. under various weed management systems in Mediterranean climate …………………………………………….…………. 74 Abstract ………………………………………..…………………………….. Introduction …………………………………………………………….…… Materials and methods ……………………………………………………... Model structure …………………………………………………………… Parameterization ………………………………………………………….. Scenarios simulated ………………………………………………………. Sensitivity analysis ……………………………………………………….. Results ………………………………………………………………………... Simulation runs …………………………………………………………… Behaviour of the population in the absence of control practices …….. The effect of individual control tactics ……………………………….. Assessing integrated programs ……………………………………….. Sensitivity analysis ……………………………………………………….. Discussion ……………………………………………………………………. References …………………………………………………………………….

75 76 77 77 79 85 86 86 86 86 87 87 88 88 90

CHAPTER 4 PRIM (Poppy Resistant Integrated Management): a bio-economic model for Papaver rhoeas L. in rainfed cropping systems …………………………………………………………...…….………...

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Abstract ………………………………………..……………………………. Introduction ………………………………………………………………… Materials and methods …………………………………………………….. Model description ……………………………………………………….. Model development ……………………………………………………… Population dynamics ………………………………………………… Effects of tillage systems on seed bank and emergence ……………... Weed-crop competition ……………………………………………… Biomass and seed production ……………………………………….. Crops ………………………………………………………………… Weed control ………………………………………………………… Economic Values …………………………………………………….. Limitations ………………………………………………………………. Model validation ……………………………………………………………. Seed bank ……………………………………………………………….. Mature plants ……………………………………………………………. Sensitivity analysis …………………………………………………………. Uncertain parameters ……………………………………………………. Sensitivity indices ……………………………………………………….. Simulation …………………………………………………………………... Conclusions ………………..……………………………………………….. References ………………………………………………………………….. Appendix …………………………………………………………………….

95 96 98 98 99 99 100 102 103 105 105 107 108 108 110 112 114 115 115 117 119 120 125

CHAPTER 5 General conclusions ……………………………………..

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PRESENTACIÓ

Aquesta tesis s’ha realitzat sota la direcció del professor Dr. Jordi Recasens Guinjuan i dins del grup de recerca consolidat de Malherbologia del Departament d’Hortofructicultura, Botànica i Jardineria de l’Escola Tècnica Superior d’Enginyeria Agrària (ETSEA) de la Universitat de Lleida. El present treball s’emmarca dins un projecte de recerca del Plan Nacional I+D (Manejo de poblaciones de Papaver roheas y Lolium rigidum resistentes a herbicidas) finançat per fons FEDER i pel Ministerio de Educacion y Ciencia (Projecte AGF 2002-01513) i desenvolupat entre als anys 2002 i 2005. La Universitat de Lleida em va concedir una beca de doctorat des de l’abril de 2003 fins a l’abril de 2007. Durant la realització d’aquesta tesis s’han dut a terme tres estades en altres centres d’investigació, tant a nivell estatal com internacional, gràcies a diversos ajuts per realitzar estades de recerca a l’estranger atorgats per la mateixa universitat: - De l’1 d’agost al 30 de setembre de 2004: al Horticulture Research and Development Centre de Saint Jean sur Richelieu de Quebec (Canadà), amb la Dra. Diane Benoit. - De l’1 al 30 de setembre de 2005: al Instituto de Agricultura Sostenible del CSIC de Córdoba amb el Dr. José Luís González Andújar. - Del 27 de gener al 27 de Novembre de 2006: al Departament Western Australian Herbicide Resistant Initiative (WAHRI) de la University of Western Australia de Perth (Austràlia) amd el professor Dr. Stephen Powles.

A partir dels resultats obtinguts durant el desenvolupament de la tesis, s’han elaborat diferents articles per a revistes i presentats treballs en diferents congressos que ressenyem a continuació: - Article 1: Relationship between emergence time and seedling recruitment, survival, development, reproduction and dormancy in Papaver rhoeas. J. Torra i J.Recasens. Enviat a la revista Weed Science a principis de maig de 2007. - Article 2: Herbicide Resistant Corn Poppy (Papaver rhoeas) Control in Winter Cereal with Postemergence and Preemergence Herbicides. J. Torra, A. Taberner i J. Recasens. Enviat a la revista Weed Technology a finals de març de 2007. 1

- Article 3: Modeling the long term population dynamics of poppy (Papaver rhoeas) under various weed management systems in Mediterranean climate. J. Torra, J. L. González Andújar i J. Recasens. Enviat a la revista Weed Research a finals de octubre de 2006. - Article 4: PRIM (Poppy Resistant Integrated Management): a bio-economic model for Papaver rhoeas in rainfed cropping systems. J. Torra, A. Cirujeda, J. Recasens, A. Taberner i S. Powles. Enviat a la revista European Journal of Agronomy a finals de març de 2007.

A més, durant el transcurs del present treball s’ha dut a terme la difusió dels resultats obtinguts a diversos congressos d’àmbit nacional i internacional: - Persistencia del banco de semillas e influencia de las labores del suelo en poblaciones de Papaver rhoeas y Lolium rigidum resistentes a herbicidas. J. Torra, A. Cirujeda, J. Planes, J. Aibar, A. Taberner i J. Recasens. IX Congreso de la Sociedad Española de Malherbología (SEMh) a Barcelona del 4 al 6 de novembre de 2003. - Control per mètodes químics, mecànics i culturals, d’una població de rosella (Papaver rhoeas L.) resistent al 2,4-D. J. Torra, D. Giné i J. Recasens. VI Jornada de Protecció Vegetal de la Institució Catalana d’Estudis Agraris (ICEA) a Barcelona el 6 de febrer de 2004. - Control of herbicide resistant corn poppy (Papaver rhoeas L.) populations by cultural, chemical and mechanical methods. J. Recasens, J. Torra, M. M. Ribalta i A. Taberner. XII Colloque International sur la Biologie des Mauvaises Herbes a Dijon (França) del 31 d’agost al 2 setembre de 2004. - Influence of temperature and photoperiod on early development of Papaver rhoeas. J. Torra, D. L. Benoit, G. Bourgeois i J. Recasens. LVIII Congress Canadian Weed Science Society del 29 de novembre a l’1 de desembre de 2004 a Winnipeg (Canadà). - The effect of different fallow management within a cereal system on a herbicideresistant Papaver rhoeas L. Population. J. Recasens, J. Torra, M.M. Ribalta i A. Taberner. XIII Symposium European Weed Research Society (EWRS) a Bari (Itàlia) del 20 al 23 de juny de 2005. - Aplicación del modelo no linear de Weibull al desarrollo de Papaver rhoeas y Lolium rigidum. J. Torra, J. Planes i J. Recasens. El manejo de barbechos en el control de poblaciones de malas hierbas resistentes a herbicidas. J. Torra, M. M. Ribalta, A.

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Taberner i J. Recasens. X Congreso de la Sociedad Española de Malherbología (SEMh) a Huelva del 7 al 9 de novembre de 2005. - Seed dormancy in Papaver rhoeas is affected by the time of emergence of mother plants. J. Torra i J. Recasens. XV Australian Weeds Conference a Adelaida (Austràlia) del 24 al 28 de setembre de 2006. - PRIM (Poppy Resistant Integrated Management): a bio-economic model for Papaver rhoeas in the North-East of Spain. J. Torra, A. Cirujeda, A. Taberner, J. Recasens i S. Powles. Seed production in Papaver rhoeas affected by time of emergence and crop competition. J. Torra i J. Recasens. XIV Symposium European Weed Research Society (EWRS) a Hamar (Noruega) del 18 al 21 de juny de 2007.

Articles en revistes de divulgació: - J. Recasens i J. Torra. 2005. Manejo de poblaciones de Papaver rhoeas resistentes a herbicidas. Phytoma 173, 101-108. - J. Recasens i J. Torra. 2006. El manejo de barbechos en el control de poblaciones de amapolas (Papaver rhoeas L.) resistentes a herbicidas. Tierras de Castilla y León 130, 13-19.

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AGRAÏMENTS

Aquesta és una llarga història que poca gent coneix en tot detall, i la qual he d’agrair al professor Jordi Recasens, director d’aquesta tesis, però un bon amic abans que res.

Tot va començar l’agost de 2002 quan vam tenir la primera entrevista a la Unitat de Botànica de la Facultat de Biologia de Barcelona. Qui havia de dir que arribaríem tan lluny, Jordi, i més sobretot quan al setembre ens van comunicar que la beca associada al projecte no havia estat concedida. A partir d’aquí, ens les vam trampejar com vam poder, des de beques d’anar per casa, fins a professor associat del departament. Tot i que a la llarga, tot té els seus avantatges, perquè finalment quan em van concedir la beca de doctorat de la Universitat de Lleida, ja portava pràcticament una campanya a les esquenes. I aquí ens trobem ara, al maig de 2005, a punt d’esdevenir doctor i amb un munt de històries i anècdotes per explicar.

Està clar que sense l’ajut de l’Andreu Taberner, l’Antonio Roque i l’Alicia Cirujeda, els inicis d’aquesta tesis haurien estat bastant complicats. Gràcies.

Evidentment, sense els pagesos que ens van cedir els seus camps de conreu, Salvador Soldevilla i Jaume Cunyat a Cubells, i el pagès d’Almacelles, aquesta història no hagués ni començat.

La Sandra i la Núria van ser els primeres persones que en van introduir en el departament de Hortofructicultiura. Botànica i Jardineria, a tots els membres del qual (Josep Anton, Joan i un llarg etcètera) també vull mostrar el meu agraïment. També estic agraït al Jair i la Laura, els estudiants de “l’altre edifici”.

Durant la realització d’aquesta tesis unes quantes persones han passat per la nostre grup de Malherbologia, per realitzar TPTs i projectes finals de carrera, sense l’ajuda dels quals molta de la feina realitzada no hagués estat possible. A tots, us garanteixo una caragolada de les que ja sabeu, que segur que és en l’únic que esteu pensant.

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El primer de tots va ser el David, i el primer sempre serà el primer. Amb tu vaig conèixer l’altra cara d’agrònoms, la del dijous a la nit. Després va passar el Jaume, sense el qual, l’assaig de demografia (no projectat inicialment) no hagués estat possible. I mira, s’ha acabat convertint en un dels pilars d’aquesta tesis.

Després, les coses van millorar, i seguint els meus savis consells el Jordi va començar a agafar noies en lloc de nois. No és res personal, xavals. La Mar, va ser la primera, i com torno a repetir, la primera és sempre la primera. Recordes aquells dies tant llargs de mai acabar del juliol de 2004? Tot seguit va aparèixer la Jerònia, i els experiments de dormició.

Després hi va haver l’Àngels del projecte “Galium”, que juntament amb l’Aritz, el seu suport no ha tingut preu. La connexió catalano-basca també ha produït uns resultats inesperats però no menys importants.......

La primera estada a l’estranger és gràcies a la Diane Benoit. Merci beaucoup.

La segona, i més impressionant, es fruit de que el professor Stephen Powles es fixés en mi. Encara no ho entenc perquè s’hi va fixar. Thanks a lot for everything. WAHRI, and all his members (Roberto, Alberto, Shane, Robert, Michael, Fiona, Art, etc.) will a part of this thesis for ever. And of course, to Victoria, a part of my life for ever.

And finally but not less important, to the “seed predation people”, Paula, Bàrbara and Eva. Paula maybe you should go to the second or third place, for sure. But I wanted to follow a cronological order more or less.

Eskerrik asko, Ainara, Maite zaitut.

Per acabar, a la meva familia, Toni, Enedina, Sandra, Eric, padrina, àvia, Alexandra, Iuca, etc. No calen paraules.

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SUMMARY

The life cycle and the management options for different herbicide resistant Papaver rhoeas L. populations were studied in cereal fields in dry-land areas of northeastern Spain. Two fields were known to contain populations resistant to 2,4-D, and another one had a population resistant to 2,4-D and tribenuron.

Results of this research indicated that seedling emergence, growth, seed production and dormancy of seeds differed among cohorts of P. rhoeas, showing the importance of emergence time and crop competition on the fecundity and demography of this species. In later emerged cohorts and/or in the presence of barley competition, development, biomass accumulation and seed production were reduced. Furthermore, germination of harvested seeds was less for earlier than for later emerged cohorts. It seems important to prevent seedling establishment of P. rhoeas during the period corresponding to the first flushes of seedling emergence (September to January). Cohorts emerged mainly during the crop sowing are the main target for weed control management strategies. Moreover, seeds produced in autumn-winter with higher seed dormancy will be the main contributors to the seed bank and weed population in next generations.

Field trials indicated that very good control of herbicide resistant P. rhoeas in winter cereals can be achieved with trifluralin plus linuron and pendimenthalin plus linuron as pre-emergence treatment. In post-emergence, the best performances were achieved with the mixture bromoxynil plus ioxynil plus mecoprop.

A mathematical model was used to describe the behaviour of the population dynamics of P. rhoeas and to predict the effect of various control strategies and integrated weed management (IWM) scenarios. Either the application of POST herbicides, PRE herbicides or their yearly rotation did not prevent the population increase. Using various types of cultural control tactics (delayed seeding, harrowing, and fallow incorporation), resulted in different trends in the overall population, depending on the techniques and combinations analysed. Simulations showed that delayed seeding, fallow incorporation and herbicides applied in pre-emergence are the

6

best techniques to employ in IWM programs, always using a combination of these and other more common practices.

A bio-economic model for P. rhoeas for dry-land cropping systems in Spain has been developed and it can be used to evaluate weed management scenarios by investigating the implications of different tillage, fallow and cereal rotational sequences and of constraints on herbicide availability. Model validation showed that PRIM is sufficiently accurate for predicting P. rhoeas population dynamics. The most sensitive biological parameter for population dynamics prediction is the P. rhoeas emergence from 0 to 5 cm, followed by the initial seed bank density within the 0 to 5 cm soil depth. The sensitivity analyses showed that strategies linked to cost related parameters (i.e. tillage operations depending on fuel cost), and to profit related parameters (i.e. price and weed-free yield of cereals), will drive management decisions. Using PRIM, farmers will realize that reducing costs and increasing incomes are the objectives.

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SUMARIO

En el presente trabajo se han estudiado el ciclo biológico y las diferentes opciones de manejo, en sistemas cerealistas de secano, de diferentes poblaciones de Papaver rhoeas L. resistentes a herbicidas. El estudio se ha llevado a cabo en dos campos comerciales con sendas poblaciones resistentes al 2,4-D, y en un tercer campo con presencia de una población con resistencia múltiple a 2,4-D y a tribenurón-metil.

Se ha observado que diferentes parámetros demográficos y fisiológicos como la emergencia de plántulas, su desarrollo, fecundidad y dormición de las semillas producidas, difieren entre les diferentes cohortes establecidas. Se ha constado igualmente la importancia de la relación entre el momento de emergencia y/o de la competencia con el cultivo, con la fecundidad y demografía de esta especie. En cohortes tardías y/o con competencia con cebada, el crecimiento, la acumulación de biomasa y la producción de semillas se redujeron. Además, la germinación de semillas producidas por parte de cohortes tardías ha estado superior a la de las cohortes más precoces. Se ha constatado además, la importancia de prevenir el establecimiento de plántulas de P. rhoeas durante el período correspondiente a los primeros picos de emergencia (setiembre a enero). Las cohortes emergidas durante la siembra del cereal son las que han de ser objetivo principal de las estrategias de control, debido además, al hecho que las semillas que producen muestran mayor dormición y serán las principales contribuyentes al banco de semillas y al incremento poblacional en años siguientes.

En los ensayos de campo realizados, se ha comprobado un muy buen control de las poblaciones resistentes mediante las materias activas trifuralina + linurón y pendimentalina + linurón en pre-emergencia. En post-emergencia, las mejores eficacias se han obtenido con la mezcla bromoxinil + ioxinil + mecoprop.

Se ha usado un modelo matemático para describir la dinámica de poblaciones de P. rhoeas y poder así predecir el efecto de diversas estrategias de control y, en definitiva, de programas de control integrado (IWM). La aplicación de herbicidas en post-emergencia, en pre-emergencia o su alternancia anual, no ha evitado un incremento de la población. Diversos tipos de tácticas de control y la combinación de ellas (retraso de siembra, control mecánico con grada de púas, o incorporación de un año de 8

barbecho), han dado como resultado diferentes tendencias poblacionales. Las simulaciones han demostrado que el retraso de siembra, el barbecho y la utilización de herbicidas de pre-emergencia, son las mejores tácticas a utilizar en programas de IWM.

Se ha desarrollado, asimismo, un modelo bio-económico para el manejo de P. rhoeas resistente a herbicidas en sistemas cerealistas de secano (PRIM). Este modelo puede ser usado para evaluar programas de IWM y a la vez analizar las consecuencias de diferentes labores del suelo, incorporación de barbechos y rotaciones de cultivos y de diferentes restricciones según la disponibilidad de herbicidas. La validación del modelo ha mostrado que PRIM es suficientemente preciso para predecir la dinámica de poblaciones de P. rhoeas. Los parámetros más sensibles del modelo fueron la emergencia de semillas entre 0 y 5 cm de profundidad en el suelo, seguido de la densidad del banco de semillas a la misma profundidad. El análisis de sensitividad ha mostrado que las estrategias relacionadas con parámetros de costes (p. e., labores del suelo), y parámetros de beneficios (p. e., el precio y máximo rendimiento de los cereales), son, en definitiva, los que hacen dirigir las decisiones de manejo.

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RESUM

En el present treball s’ha estudiat el cicle biològic i les diferents opcions de maneig, en sistemes cerealistes de secà, de diferents poblacions de Papaver rhoeas L. resistents a herbicides. El treball s’ha portat a terme en dos camps comercials amb sengles poblacions resistents al 2,4-D, i en un tercer camp amb presència d’una població amb resistència múltiple a 2,4-D i a tribenurón-metil.

S’ha observat que diferents paràmetres demogràfics i fisiològics com l’emergència de plàntules, el seu desenvolupament, fecunditat i dormició de les llavors produïdes, difereixen entre les diferents cohorts establertes. S’ha constatat igualment la importància de la relació entre el moment d’emergència i/o de la competència amb el cultiu, amb la fecunditat i demografia d’aquesta espècie. En cohorts tardanes i/o amb competència amb ordi, el creixement, l’acumulació de biomassa i la producció de llavors es redueix. A més, la germinació de llavors produïdes per part de cohorts tardanes ha estat superior a la de les cohorts més precoces. S’ha constatat a més, la importància de prevenir l’establiment de plàntules de P. rhoeas durant el període corresponent als primers pics d’emergència (setembre a gener). Les cohorts emergides de manera coincident amb la sembra del cereal són les que han de ser objectiu principal de les estratègies de control, degut a més, al fet que les llavors que produeixen mostren major dormició i esdevenen les principals contribuents al banc de llavors i en definitiva a l’increment poblacional en anys següents.

En els assaigs de camp realitzats, s’ha comprovat un molt bon control de les poblacions resistents mitjançant les matèries actives trifuralina + linuró i pendimentalina + linuró en pre-emergència. En post-emergència, les millors eficàcies s’han obtingut amb la barreja bromoxinil + ioxinil + mecoprop.

S’ha emprat un model matemàtic per descriure la dinàmica de poblacions de P. rhoeas i poder així predir l’efecte de diverses estratègies de control i, en definitiva, de programes de control integrat (IWM). L’aplicació d’herbicides en post-emergència, en pre-emergència o la seva alternança anual, no ha evitat un increment de la població. Diversos tipus de tàctiques de control i la combinació d’elles (retràs de sembra, control mecànic per grada de pues, o incorporació d’un any de guaret), han donat com a resultat 10

diferents tendències poblacionals. Les simulacions han demostrat que el retràs de sembra, el guaret i la utilització d‘herbicides de pre-emergència, esdevenen les millors tàctiques a utilitzar en programes de IWM.

S’ha desenvolupat, tanmateix, un model bio-econòmic per al maneig de P. rhoeas resistent a herbicides en sistemes cerealites de secà (PRIM). Aquest model pot ser utilitzat per avaluar programes de IWM i alhora analitzar les conseqüències de diferents labors del sòl, incorporació de guarets i rotacions de cultius i de diferents restriccions segons la disponibilitat d’herbicides. La validació del model ha mostrat que PRIM es prou acurat com per predir la dinàmica de poblaciones de P. rhoeas. Els paràmetres més sensibles del model van ser l’emergència de llavors entre 0 i 5 cm de profunditat en el sòl, seguit de la densitat del banc de llavors entre aquests mateixos nivells de profunditat. L’anàlisi de sensitivitat ha mostrat que les estratègies relacionades amb paràmetres de costos (p. e., labors del sòl), i paràmetres de beneficis (p. e., el preu i màxim rendiment dels cereals), són, en definitiva, les que fan dirigir les decisions de maneig.

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SCOPE OF THE STUDY

Setting the scene

Winter cereals in Spain are mainly sown under rain fed conditions and cultural practices can vary a lot regarding precipitation availability (Fernandez-Quintanilla et al., 1999). In the dry-land areas, with less than 400 mm of annual rain and low average yields, choices are very restricted for weed management. Conversely, in moister areas or under irrigation, farmers have more available options for weed control.

Before synthetic herbicides were introduced in the 1950s, in the dry-land areas of the north-east of Spain, the only possible alternative used by farmers was the incorporation of a fallow year to preserve soil humidity and reduce weed populations. Occasionally, some legumes were used in rotation with cereals. With higher moisture, other crops were available for growers, i.e. legumes, alfalfa or potatoes (Taberner et al., 1992), and today others are being introduced in these areas (canola or sunflower).

However, the field management in the dry-land areas of the north-east of Spain has changed in the last decades. With the appearance of herbicides, together with mechanization, practices like ploughing, hand weeding or fallow started to disappear. Nowadays, cereal monocrop (only barley in the drier areas of Catalonia) under conventional tillage and post-emergence herbicides as the major strategy is the common situation. In Spain, the production of winter cereals is around 19 tones of harvested grain, with a cropped surface of 5.8 millions of sown hectares (MAPA, 2007).

The introduction of herbicides into agricultural systems and their subsequent efficiency in maintaining crops relatively free from competition, led initially to the idea that a complete weed eradication was possible. It soon became evident, however, that weed eradication was not a reasonable target and that infestation levels had not decreased to the extent that had been expected. In fact, continuous use of herbicide prompted the appearance of resistant weed biotypes and contamination of the environment (Garcia-Martin et al., 2007). Previous to the introduction of 2,4-D, dicotyledonous weeds like Papaver rhoeas L. dominated in the north-east of Spain, but with its continuous application promoted grass weeds to become the main problem. 12

With the appearance of herbicides of the urea group enhanced by the growing herbicide resistance to 2,4-D, the broadleaf weeds were the protagonists again. Afterwards, the appearance of the sulfonylureas in the 80’s solved the question for a while dicot weeds were replaced another time. But herbicide resistance towards this new group started already five or six years afterwards and placed the P. rhoeas management into a difficult situation once more.

The weed study case

In these conditions, Papaver rhoeas (Papaveraceae), is the most important dicot weed species infesting winter cereals in north-eastern Spain (Riba et al., 1990). Because of high fecundity, long persistence in the seed bank, and an extended period of germination, P. rhoeas is difficult to control, and it is also a competitive weed that can substantially reduce grain yields (Holm et al., 1997; McNaughton and Harper, 1964; Wilson et al. 1995). Control became worse with the appearance of herbicide resistant biotypes. Problems in controlling P. rhoeas with herbicides in winter cereals have been reported in Spain since 1992 (Taberner et al., 1992). In 1998, Claude et al. reported the first case of a P. rhoeas population resistant to 2,4-D and to tribenuron-methyl. In a non-random survey conducted in north-eastern Spain between 1990 and 2001 where 134 populations were sampled, 85% were found to be resistant to 2,4-D, 72% to tribenuron-methyl to some extent, and 58% to both herbicides (Cirujeda, 2001).

Knowledge on Papaver rhoeas

Biology

Several are the studies analyzing the emergence period of P. rhoeas in cereals. It is known that this species is able to germinate from September to April being the highest rates between October and February (Izquierdo and Recasens, 1992; McCloskey et al., 1998). Several authors have also reported very low seed bank expression for P. rhoeas, the percentage ranging from less than 1 to 10 % (Beuret, 1989; Lovato and Viggiani, 1974; Roberts and Ricketts, 1979; Roberts, 1984; Barralis et al., 1988). Seed bank decline over time have estimated for P. rhoeas: Barralis et al. (1988) cited an annual decay of 40% in cultivated soils; Milberg and Anderson (1997) reported that 13

25% of seeds lost viability in 14 months; in addition, Wilson and Lawson (1992) estimated 35% of seed bank mortality for cultivated soils.

The reproductive capacity is also well known and studied in competition with cereals in UK (Wilson et al., 1988; 1995; Wright, 1993), and its huge fecundity has been reported, with 800.000 seeds plant-1 with no competition, and 40.000 seeds plant-1 with wheat competition (Holm et al., 1997). Other studies have analyzed the germination characteristics of the species (Baskin et al., 2002; Milberg and Andersson, 1997) and others have stated the high persistence in the soil of P. rhoeas seeds (Lutman et al., 2002; Cirujeda et al., 2006). These studies indicate that process is an annual conditional dormancy/non-dormancy cycle in buried seeds of P. rhoeas.

However, most of these studies were not undertaken in winter cereals in Mediterranean conditions. This knowledge is required to improve weed treatments and develop better models for weed management regionally adapted (Powles and Bowran, 2000).

Control techniques

In the absence of control practices, the P. rhoeas high potential of infestation has been reported by Lintell-Smith et al. (1991, 1992) and Roberts and Chancellor (1986), who found that in a single year of chemical control failure the seed bank increased from 580 to 21000 seeds m-2. For this reason, achieving a good weed control is mandatory.

Herbicides applied in post-emergence are the most common method used in Spain to control P. rhoeas both under zero and conventional tillage. Non-selective presowing herbicides applied under direct drilling are very common, and selective preemergence herbicides are not used under any tillage situation. Following the coming of herbicide resistant populations, several studies have been done to test different preemergence and post-emergence herbicides in Europe, usually with average efficacies greater than 90%, varying with the type of compounds and environmental conditions from 70% to 100% (Cirujeda, 2001; Froment and Turley, 1998; Frost, 1982; Rapparini, 2001).

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Much work has been done on P. rhoeas mechanical control by harrowing as an alternative technique to herbicides with the appearance of herbicide resistant biotypes (Cirujeda et al., 2003a; Cirujeda et al., 2003b; Lacasta et al., 1997; Welsh et al., 1997; Caseley et al. 1993). Efficacies in these studies ranged from 58 to 95%, ant it is indicated that the level of control is very sensitive on the soil type, weed density, weather conditions, etc (Melander et al., 2003).

Cultural practices

Conversely, other strategies that have been proved to be useful in controlling other weed species are not common for P. rhoeas control in Spain. For other weeds in cereal crops, the incorporation of one fallow season (Daugovish et al., 1999, GonzalezAndujar and Fernandez-Quintanilla, 1991) or delaying the crop sowing date (Gill and Holmes, 1997) can promote a depletion of seed bank and better weed control during the next crop season. For example, in a study in UK it was found that fallow can rapidly decrease P. rhoeas seed bank (Brenchley and Warington 1945).

Using crops that are sown in spring and summer allows breaking the life-cycle of the weeds that emerge in autumn and winter, the main ones in winter cereals, as P. rhoeas. Very studies are available in terms of the effects of crop rotations on P. rhoeas populations dynamics. Dorado et al. (1999) found that under the rotations barleysunflower or barley-vetch, the weed densities and seedbank increased. Anyway, in large areas of north-eastern Spain, because of the limited rainfall restricted crop choices are available.

Regarding tillage systems, traditionally, the stale bed preparation in winter cereals included a mouldboard ploughing followed by one or several secondary cultivations with chisel or tine harrow, allowing physical weed control and deepening weed seeds from previous season. Due to the high cost, slowness and erosion risk ploughing has been abandoned and conventional tillage is much more common, with direct drilling starting to spread. The effects of tillage systems on P. rhoeas seed bank are not clear. Robert and Feast (1973) found out that seed bank densities decreased more rapidly with cultivation than without. Similar to these results, FernandezQuintanilla et al. (1984) observed lower weed densities in plots under zero tillage than 15

in plots under conventional tillage. On the other hand, other studies showed that P. rhoeas densities were significantly higher in zero or non-tillage systems than in mouldboard or conventional tillage systems (Dorado and Lopez-Fando, 2006; Navarrete et al., 2005).

Integrated Weed Management (IWM)

Concerns over pesticide resistance, environmental and health hazards of pesticides, and declining profitability led to the development of the concept of integrated pest management (IPM), IWM for weeds. IPM involves the concerted use of multiple tactics to suppress and kill pests and reduce crop damage to economically acceptable levels (Bottrell, 1979). A key component of IWM is the knowledge on 1) crops and weeds biology, 2) weeds abundance and distribution, 3) impacts of environmental factors and farming practices on crop-weed interactions, 4) cost and income implications of different management options, and 5) human health and environmental impacts of different management options (Liebman et al., 2001).

In the only study exploring IWM strategies for P. rhoeas control, it was found that the combination of single ploughing and harrowing induced the lowest weed emergence, and that occasional ploughing was an effective method for placing P. rhoeas seeds in non-optimal germination situations (Cirujeda et al., 2003b).

Modelling

The detailed evaluation of the importance of the biological treats (seed bank, dormancy, emergence patterns, seedling survival, reproductive fitness, …), and of the control practices over population dynamics contribute to a better comprehension of the long-term dynamics of weeds and it can be a valuable information that drives to a more rational management of weeds. Conversely, getting all this information usually requires long and complex studies (herbicide efficacies and other control tactics, the weed-crop competition, life-cycle of the weed) that quite often are almost impossible to undertake.

A common alternative is the long-term simulation of the weed population dynamics under determined conditions using modelling (i.e. Holst et al., 2007; 16

Gonzalez-Andujar and Fernandez-Quintanilla, 2004; Munier-Jolain et al., 2002). The use of mathematical models in the study of population dynamics allows obtaining a synthetic view of the long-term evolution of weed populations. On the other hand, these models are also useful to detect which are the key biological treats that drive the population, and to develop better IWM strategies. Moreover, models are very useful to spot important lacks of knowledge, maybe otherwise not detectable, and to drive required further research.

For this reason, due to the lack of work done on P. rhoeas population dynamics modelling, this study proposes this approach.

Economics

Given that a weed seedbank of zero is unattainable, one must ask what level of control can be justified in the long run under the constraints set extrinsically by economy and climate and intrinsically by weed and crop biology (Holst et al., 2007).

An additional factor motivating the development of ecologically based weed management strategies is the need to increase farm profitability. The economics viability of many farmers has been challenged as input costs rise faster than the market values of the crops they produce. Weed management strategies that make better use of ecological processes may improve profitability by reducing production costs and helping farmers produce crops that are worth more in the marketplace (Liebman et al., 2001).

Bio-economic models of crop production systems have been developed to assess management strategies for irrigation scheduling, insect pest management, weed management, soil fertility management, and field time management (King et al., 1993). As the complexity of weed management increases, more information must be integrated to make the best weed control decisions possible. This requires the integration of a wide array of information, including weed biology, crop yield potential, efficacy of herbicides and mechanical control practices, economics, labour requirements, environmental risks, and other factors (Buhler et al., 1996). With the difficulty in estimating the economic costs and benefits of weed management systems, only limited 17

work has been conducted on the optimal economic integration of weed management practices (e.g. Gorddard et al., 1995, 1996; Schmidt and Pannell, 1996a, 1996b; Orson, 1999; Pannell and Zilberman, 2001). Recently, two bio-economic models for the management of weeds in cropping systems have been developed and used in Australia (Monjardino et al., 2003, 2004a, 2004b, 2005; Pannell et al., 2004). All these models are valuable tools for evaluating the economic and biological effectiveness of weed management strategies. While in the last 20 years the number of bio-economic models has increased, few of them have taken into account different tillage practices and their effects on population dynamics of herbicide resistant weeds in winter cereals in Mediterranean conditions in Europe.

This study proposes to capture most of the complexities associated with IWM by developing and using a suitable bio-economic modelling tool. This extension model has been constructed using the data from this Thesis and all the information available on P. rhoeas.

OBJECTIVES

The main objectives of this study were:

1) To study the different aspects of the whole life-cycle of Papaver rhoeas in winter cereal fields that are important to develop IWM strategies and models.

Analyze the relationship between emergence time and seedling recruitment, survival, development and reproduction.

Analyze the requirements (burial time, stratification temperature and temperature) for seed germination and the relationship between the seed dormancy and the emergence time of the mother plant.

2) To study different chemical control strategies in order to offer a wide range of management possibilities to farmers with herbicide resistant P. rhoeas.

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Analyze different herbicides in order to test their efficacy on herbicide resistant P. rhoeas.

3) To use modelling for the development of IWM for herbicide resistant P. rhoeas in the study area.

Develop a population dynamic model for P. rhoeas in winter cereals using the data obtained in this work to analyze the long-term effects of different IWM strategies.

Develop a bio-economic model for P. rhoeas integrated management in dry-land cereal systems using the available data nowadays on this species.

Therefore, provide the tools for the development of Integrated Weed Management strategies for herbicide resistant P. rhoeas in the study area.

EXPERIMENTAL PROTOCOL

For these reasons, it was decided to carry out several experiments, both field trial and laboratory experiments. These were a trial to deepen in knowledge of P. rhoeas lifecycle, another two to analyze the effect of different control strategies on the weed, and the last one to test the efficacy of different herbicides. This Thesis is based on these four experiments carried out in commercial fields in Cubells and Almacelles (Lleida, Catalonia, Spain) with known 2,4-D or 2,4-D/tribenuron resistant P. rhoeas populations. Laboratory experiments were undertaken for a better understand of seed dormancy processes in this species.

Field trial experiments

Trial 1 was conducted during two seasons (2003-04 and 2004-05) in a field in Cubells with a 2,4-D resistant population. It was used to analyze the demography of P. rhoeas in the absence of weed control with or without cereal competition. In both seasons barley cv. “Graphic” was sown at 200 kg ha-1 in November. The design was a 19

complete randomized block design with four replicates. Each block consisted of one plot (2 m x 1 m). In each plot three permanent quadrats, 0.33 cm wide and 0.33 cm long were established. In one quadrat of one plot seedlings were individually marked and monitored to estimate seedling survival. Seedling survival, development, reproduction and cohort structure were studied.

Trial 2 was carried out during four cropping seasons (2002-03, 2003-04, 200405 and 2005-06), in the same field as described above, to evaluate the effect of six different weed management systems on P. rhoeas in winter wheat. The design was a randomized block design with three replicates and six plots (8 m x 10 m) per replicate, corresponding to six management treatments. Weed densities were counted periodically in five permanent quadrats (0.1 m2) per plot. P. rhoeas seed bank densities were estimated from 20 soil cores of 4.6 cm diameter and 10 cm deep taken at seeding date in each of the three seasons. Seed bank density was estimated from the total number of seedlings that emerged from the soil between October and March in greenhouses (Barralis and Chadoeuf, 1987). The management systems studied were: 1) wheat monocrop with herbicide application each season; 2) wheat in 02/03, 04-05 and 05-06 and barley in 03/04 with delayed seeding (45-60 days) and herbicides all seasons; 3) fallow in 02/03 with a persistent herbicide, and wheat next seasons with herbicides as control method; 4) Fallow in 02/03 with non persistent herbicide and wheat next seasons with herbicides as control method; 5) fallow in 02/03 and wheat next seasons with mechanical harrowing; and 6) fallow in 02/03 and wheat next seasons with soil ploughing before sowing and mechanical harrowing.

Trial 3 was conducted in the same field as trial 2 during seasons (2002-03, 200304 and 2004-05), using the same crop (wheat), plot size, and methodology to follow weed and seed bank densities as detailed for trial 2. The goal was to evaluate the effect of different cultural practices on seed bank densities and emergence of P. rhoeas. A split-block design with three replicates was used. The main factor was the type of field management that was carried out between wheat harvest in summer and sowing of the subsequent crop in autumn corresponding to A) shallow cultivation before crop sowing each season; B) shallow cultivation before sowing each season and mouldboard ploughing after harvest the first two seasons; C) shallow cultivation before sowing each season and mouldboard ploughing after harvest the first season and mulching the 20

second one; and D) shallow cultivation before sowing and mouldboard ploughing before sowing the first season and shallow cultivation before sowing with straw burning after harvest the first two seasons. Weed control strategy, either chemical control with herbicides or mechanical control by harrowing, was the secondary factor. Seed bank densities were estimated as described above for trial 2.

Trial 4 was conducted during three years (2002-03, 2003-04 and 2004-05) in three commercial winter barley fields, one was the same field as described above, the second was also located in Cubells with 2,4-D/tribenuron resistant populations, and the last one was located in Almacelles with a 2,4-D resistant population. The purpose was to evaluate the efficacy of a broad spectrum of herbicides on P. rhoeas control. Barley cv. “Graphic” was seeded at 200 kg ha-1. A randomized block design with three replicates, and 11 plots per block (seven treated and four adjacent untreated between the treated plots), was used. A plot measured 10 m x 2 m. Herbicide applications were made with a constant pressure hand-field plot sprayer at 253 kPa using a total volume of 300 L ha-1. The different pre-emergence and post-emergence herbicides were applied in the recommended doses in each block. 15, 30 and 60 days after herbicide application weed densities were estimated within five, 0.10 m2 quadrats per plot. Efficacy was calculated using Abbot’s formula (Abbot, 1925).

Laboratory experiments

Seeds collected from the cohorts established in 2004 in trial 1 were used to study dormancy in P. rhoeas in two assays. In the first one, a growth chamber experiment was carried out, as a four-way full factorial design, with three stratification temperature regimes, three exhumation periods, three germination temperature regimes, and four different cohorts. For each cohort, 1000 seeds were placed inside polyester bags with an aperture