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Demography and population dynamic of the arable weed Phalaris brachystachys L. (short-spiked canary grass) in winter wheat
ARTICLE IN PRESS
Crop Protection 24 (2005) 581–584 www.elsevier.com/locate/cropro
Short communication
Demography and population dynamic of the arable weed Phalaris brachystachys L. (short-spiked canary grass) in winter wheat J.L. Gonzalez-Andujara,, M. Jimenez-Hidalgob, L. Garcia-Torresa, M. Saavedrac a
Departamento de Proteccion de Cultivos, Instituto de Agricultura Sostenible (CSIC) Alameda del Obispo, Apdo. 4084, E-14080 Co´rdoba, Spain b Departamento de Sanidad Vegetal. Delg. Prov. Agricultura., 14004 Co´rdoba, Spain c Departamento Proteccio´n Vegetal, CIFA, Alameda del Obispo s/n, 3092 Co´rdoba, Spain Received 13 September 2004; received in revised form 23 September 2004; accepted 24 September 2004
Abstract The demography of the annual grass weed Phalaris brachystachys (short-spiked canarygrass) was studied during three consecutive years in winter wheat in south Spain. The average density was 16.70 seedlings m2. The rate of seedling recruitment was 0.18. Average seedling survivorship was estimated with a value of 0.3 and was relatively uniform. Plant fecundity was calculated at 1232 seeds plant1. The annual rate of population growth was estimated based on the above-mentioned parameters. The growth rate obtained was very high (l ¼ 75:96), indicating the high potential of P. brachystachys to increase its populations in the absence of control measures. Sensitivity analysis indicated emergence, survivorship and seed losses were most sensitive to parameter variation. Management practices that reduce these parameters may result in reductions in weed populations. r 2004 Elsevier Ltd. All rights reserved. Keywords: Population growth rate; Population dynamics; Sensitivity analysis; Phalaris brachystachys; Demography; Winter wheat
1. Introduction Phalaris brachystachys L. (short-spiked canarygrass) is an annual grass which has become one of the most common and troublesome weeds in Mediterranean climates (Gonzalez–Andujar and Saavedra, 2003; Catizione and Viggiani, 1980), India (Bir and Sidhu,1979) and California (Bell, 1992). In Spain, it is abundant in the southern part of the country, where it represents a major problem in winter cereals. Gonzalez-Andujar and Saavedra (2003) reported the presence of P. brachystachys in 17% of the cereal fields surveryed. P. brachystachys is a vigorous and prolific weed that can significantly reduce wheat and barley yields (Catizione and Viggiani, 1980; Jimenez-Hidalgo, 1993; Godinho and Costa, 1981; Afentouli and Eleftherohorinos, 1996 ). Cudney and Hill (1979) found that 108 and 915 plants m2 reduced wheat yield by 40% and 60%, Corresponding author. Fax: +34 957499252.
E-mail address: [email protected] (J.L. Gonzalez-Andujar). 0261-2194/$ - see front matter r 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.cropro.2004.09.019
respectively. Afentouli and Eleftherohorinos (1999) pointed out that 152 and 304 plants m2 reduce wheat yield by 32% and 42%, respectively. In Spain 100 plants m2 reduce wheat yield by 16% (Jimenez-Hidalgo et al., 1997). The evaluation of weed management plans depends on our ability to understand and predict changes in weed populations. This explains the considerable interest in developing mathematical models based on demography studies that can be used to forecast the dynamics of weed populations (Gonzalez-Andujar and Fernandez-Quintanilla, 1991, 1993). For short-spiked canarygrass most published work is on competition with cereals, while studies on its demography and population dynamics are very scant (Jimenez-Hidalgo et al., 1990). The objectives of this study were (1) to estimate the annual rates of seedling recruitment, plant survival and plant fecundity for P. brachystachys and (2) to determine the population growth rate (l) of this species and its sensitivity to life history parameters.
ARTICLE IN PRESS 582
J.L. Gonzalez-Andujar et al. / Crop Protection 24 (2005) 581–584
2. Material and methods Experiments were conducted in a farm field at Trinidades (Cordoba, South Spain) with no previous infestation of P. brachystachys, on a vertisol soil with a pH of 8.4. Average annual rainfall in the studied area is 600 mm seasonally distributed in autumn and spring. The study was carried out during three consecutive seasons, 1988–90 during a wheat–sunflower rotation, although only in the wheat years the P. brachystachys demography can be estimated (1988 and 1990). The elemental plot was 3 6 m with three permanent replications. Each November in the wheat year, the plots were sown to winter wheat (cv. ‘Anza’ at 180/ 220 kg h1) and harvested in June. No herbicide was used to control short-spiked canarygrass. In the experiments 1150 seeds (64 seeds m2) of P. brachystachys were broadcast on the soil surface of each plot and immediately incorporated (o10 cm depth) with a field cultivator. Within each plot seedlings m2 was determined between January and March by sampling at 10 random quadrats (0.1 m2) per plot. Emergence of P. brachystachys take place predominantly in late autumn and early winter. Immediately before crop harvest, the number of plants m2 and the panicle m2 were determined by sampling at random 8 quadrat of 0.25 m2 per plot. The number of seed per panicle was determined averaging a random sample of about 80 panicles.
3. Results and discussion 3.1. Seeding recruitment The average emergence was 16.70 seedlings m2 (SE ¼ 14:78). Similar results had been obtained by Amor (1985) with Australian populations under Mediterranean climate. Other authors (Okereke et al., 1981; Yaduraju et al., 1984) found higher emergence rates, however such results were obtained under glasshouse conditions. The rate of seedling recruitment, pg, was established as the proportion of the seed bank that emerged throughout the growing season (Mortimer et al., 1980). The average rate was 0.18 (SE ¼ 0:08). 3.2. Seedling survivorship Seedling survival was not very high and relatively uniform. The rate of plant survivorship, ps, was calculated as the probability of emerged seedlings surviving to set seed. Seedling survivorship was estimated with an average value of 0.30 (SE ¼ 0:05). Some authors have reported self-regulation through densitydependent processes (e.g. Gonzalez-Andujar and
Fernandez-Quintanilla, 1991). We did not detect such processes, perhaps because they may occur only at higher density infestations. 3.3. Adult fecundity Plant fecundity, f, was calculated as the product of panicles plant1 and seeds panicle1. The panicle number was relatively stable with an average value of 6.26 (SE ¼ 1:02) panicles plant1. The average number of seeds panicle1 was 196.8 (SE ¼ 21:59). Afentouli and Eleftherohorinos (1996) reported 190 seeds panicle1 for short-spiked Canarygrass, very close to our results. Average fecundity was estimated at 1232 seeds adult plant1(SE ¼ 464:90). Total seed production per square metre (seed rain) was 5392 in 1988 and 25,101 in 1990.
4. Population dynamics The annual dynamics of the population was described using a life-cycle diagram, following the approach of Fernandez-Quintanilla et al. (1986). According to this approach, the life cycle of the plant was divided into four different functional phases: seedlings, mature plants, seed produced and seed bank (Fig. 1). All these phases were interconnected through five interphases: seedling recruitment, plant survivorship, fecundity, seed rain recruitment, seed survivorship in soil (Fig. 1). The experimental results obtained indicate that the growth of the population during the plant ‘‘phase’’ was determined by low rate of seedling emergence, low seedling survivorship and high adult fecundity. In order to estimate the overall population growth ðlÞ; we used the basic model l ¼ ð1 pg Þð1 pm Þ þ pg ps ð1 pl Þ f ,
(1)
where pg is the probability of emergence, ps is portion of emerged seedlings that survive until reproduction (seedling survival), f is the number of viable seeds produced by mature plants (fecundity), pl is the portion of all the new seeds produced that are lost (e.g. predation) and pm is the portion of seeds that are removed by natural mortality (seed mortality). As our study only covered the quantification of pg, ps and f, estimates of the two remaining parameters (pm ¼ 0:5; pl ¼ 0:34) were taken from other studies (JimenezHidalgo, 1993) Using model (1) with the values obtained in this work, it was possible to estimate annual rate of population growth. The growth rate obtained was very high (l ¼ 75:96), indicating the potential of P. brachystachys to rapidly increase its populations in the absence of control measures. The high rate of potential population growth is mainly derived from the fecundity parameter.
ARTICLE IN PRESS J.L. Gonzalez-Andujar et al. / Crop Protection 24 (2005) 581–584
583
Table 1 Demography sensitivity analysis
Seed produced
Parameter Emergence Seedbank mortality Fecundity (seeds plant1) Seedling survivorship Seed losses
f (1232) Plants
Value pg pm f ps pl
243.43 0.82 0.03 146.36 66.52
ps (0.30) pl (0.34) Seedlings
pg (0.18) Seed Bank Pm (0.5)
Fig. 1. Life-cycle of P. brachystachys in winter wheat.
In the model described previously all the parameters are assumed to be constant. In practice most of these parameters vary from year to year. To examine the sensitivity of l we need to evaluate the partial derivative of l with respect to the life history parameters (Schmidt and Lawlor, 1983). The partial derivatives for parameters are @l=@pg ¼ ps ð1 pl Þf ð1 þ pm Þ, @l=@pm ¼ 1 þ pg , @l=@f ¼ pg ps ð1 pl Þ, @l=@ps ¼ pg ð1 pl Þf , @l=@pl ¼ pg ps f . The effects of changing the values of the different parameters were generally high, indicating a high sensitivity of the model to parameter variation (Table 1). Emergence, survivorship and seed losses were most sensitive to parameter variation. It is critical, therefore, that these three parameters must be estimated with maximum precision. However, reduction in fecundity and seed bank mortality did not have much influence. The high sensitivity values estimated for these three processes suggest that using management practices that reduce, germination, survivorship or increase seed loss may result in substantial reductions in weed populations.
Acknowledgements We are greatly indebted to The Spanish Ministry of Education and Science (R+D project AGL 2002-3801) for financial support.
References Afentouli, C.G., Eleftherohorinos, I.G., 1996. Littleseed canarygrass (Phalaris minor) and short-spiked canarygrass (Phalaris brachystachys) interference in wheat and barley. Weed Sci. 44, 560–565. Afentouli, C.G., Eleftherohorinos, I.G., 1999. Competition between wheat and canarygrass biotypes and their response to herbicides. Weed Sci. 47, 55–61. Amor, R.L., 1985. Seasonal emergence of weeds typically occurring in the Victorian cereal belt. Plant Prot. Quart. 1, 18–20. Bell, C.E., 1992. Littleseed canarygrass control in cereal grains. Res. Prog. Rep. West Soc. Weed Sci., 232–233. Bir, S.S., Sidhu, M., 1979. Observations on the weed flora of cultivable lanas in Punjab-wheat fields in Patiala District. New Bot. 6, 79–89. Catizione, P., Viggiani, P., 1980. Un quadriennio di ricerche sulle falaridi infestanti il grano. Atti Giornate Fitopatologiche (Supplemento no. 3), 257–311. Cudney, D.W., Hill, J.E., 1979. The response of wheat grown with three population level of canarygrass to various herbicide treatments. Proc. West. Soc. Weed Sci. 32, 55–56. Fernandez-Quintanilla, C., Navarrete, L., Gonzalez-Andujar, J.L., Fernandez, A., Sanchez, M.J., 1986. Seedling recruitment and agespecific survivorship and reproduction in populations of Avena sterilis ssp. ludoviciana. J. Appl. Ecol. 23, 945–955. Godinho, I., Costa, J.C.A., 1981. Concorrencia da Phalaris minor Retz. na cultura trigo. I Congresso Portugue´s de Fitiatria e de Fitofarmacologia e III Symposium Nacional de Herbologia, 1980, Vol. 3, pp. 237–243. Gonzalez-Andujar, J.L., Fernandez-Quintanilla, C., 1991. Modeling the population dynamics of Avena sterilis under dry-land cereal cropping systems. J. Appl. Ecol. 28, 16–27. Gonzalez-Andujar, J.L., Fernandez-Quintanilla, C., 1993. Strategies for the control of Avena sterilis in winter wheat production systems in central Spain. Crop Prot. 12, 617–623. Gonzalez-Andujar, J.L., Saavedra, M., 2003. Spatial distribution of annual grass weed populations in winter cereals. Crop Prot. 22, 629–633. Jimenez-Hidalgo, M.J., 1993. Incidencia y evolucio´n de los alpistes (Phalaris ssp.) en el trigo (Triticum sp.). Ph.D. Thesis. Universidad de Co´rdoba, Cordoba, Spain 162pp. Jimenez-Hidalgo, M.J., Saavedra, M., Garcia-Torres, L., 1990. Nota sobre la dina´mica de poblaciones de Phalaris brachystachys. In: Congreso 1990 de la Sociedad Espan˜ola de Malherbologia, Madrid, Spain, pp. 299–306.
ARTICLE IN PRESS 584
J.L. Gonzalez-Andujar et al. / Crop Protection 24 (2005) 581–584
Jimenez-Hidalgo, M.J., Saavedra, M., Garcia-Torres, L., 1997. Phalaris brachystachys en cultivos de cereales. In: Sans, X., Fernandez-Quintanilla, C. (Eds.), Biologı´ a de las Malas Hierbas de Espan˜a. Phytoma Espan˜a, Valencia, Spain, pp. 77–89. Okereke, O.U., Blari, A.M., Caseley, J.C., 1981. Effects of depth of planting, temperature and soil moisture on seed emergence and survival in soil of Bromus sterilis and Phalaris minor. In: Proceedings of the Conference on Grass Weeds in Cereals, UK.
Schmidt, K.P., Lawlor, L.R., 1983. Growth rate projection and life history sensitivity for annual plants with seed bank. Am. Nat. 121, 525–539. Yaduraju, N.T., Caseley, J.C., Drennan, D.S.H., 1984. Some studies on germination, emergence and growth of Phalaris minor Retz and P. paradoxa L. In: Proceedings of EWRS Third Symposium on Weed Problems in the Mediterranean Area, pp. 447–454.
Crop Protection 24 (2005) 581–584 www.elsevier.com/locate/cropro
Short communication
Demography and population dynamic of the arable weed Phalaris brachystachys L. (short-spiked canary grass) in winter wheat J.L. Gonzalez-Andujara,, M. Jimenez-Hidalgob, L. Garcia-Torresa, M. Saavedrac a
Departamento de Proteccion de Cultivos, Instituto de Agricultura Sostenible (CSIC) Alameda del Obispo, Apdo. 4084, E-14080 Co´rdoba, Spain b Departamento de Sanidad Vegetal. Delg. Prov. Agricultura., 14004 Co´rdoba, Spain c Departamento Proteccio´n Vegetal, CIFA, Alameda del Obispo s/n, 3092 Co´rdoba, Spain Received 13 September 2004; received in revised form 23 September 2004; accepted 24 September 2004
Abstract The demography of the annual grass weed Phalaris brachystachys (short-spiked canarygrass) was studied during three consecutive years in winter wheat in south Spain. The average density was 16.70 seedlings m2. The rate of seedling recruitment was 0.18. Average seedling survivorship was estimated with a value of 0.3 and was relatively uniform. Plant fecundity was calculated at 1232 seeds plant1. The annual rate of population growth was estimated based on the above-mentioned parameters. The growth rate obtained was very high (l ¼ 75:96), indicating the high potential of P. brachystachys to increase its populations in the absence of control measures. Sensitivity analysis indicated emergence, survivorship and seed losses were most sensitive to parameter variation. Management practices that reduce these parameters may result in reductions in weed populations. r 2004 Elsevier Ltd. All rights reserved. Keywords: Population growth rate; Population dynamics; Sensitivity analysis; Phalaris brachystachys; Demography; Winter wheat
1. Introduction Phalaris brachystachys L. (short-spiked canarygrass) is an annual grass which has become one of the most common and troublesome weeds in Mediterranean climates (Gonzalez–Andujar and Saavedra, 2003; Catizione and Viggiani, 1980), India (Bir and Sidhu,1979) and California (Bell, 1992). In Spain, it is abundant in the southern part of the country, where it represents a major problem in winter cereals. Gonzalez-Andujar and Saavedra (2003) reported the presence of P. brachystachys in 17% of the cereal fields surveryed. P. brachystachys is a vigorous and prolific weed that can significantly reduce wheat and barley yields (Catizione and Viggiani, 1980; Jimenez-Hidalgo, 1993; Godinho and Costa, 1981; Afentouli and Eleftherohorinos, 1996 ). Cudney and Hill (1979) found that 108 and 915 plants m2 reduced wheat yield by 40% and 60%, Corresponding author. Fax: +34 957499252.
E-mail address: [email protected] (J.L. Gonzalez-Andujar). 0261-2194/$ - see front matter r 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.cropro.2004.09.019
respectively. Afentouli and Eleftherohorinos (1999) pointed out that 152 and 304 plants m2 reduce wheat yield by 32% and 42%, respectively. In Spain 100 plants m2 reduce wheat yield by 16% (Jimenez-Hidalgo et al., 1997). The evaluation of weed management plans depends on our ability to understand and predict changes in weed populations. This explains the considerable interest in developing mathematical models based on demography studies that can be used to forecast the dynamics of weed populations (Gonzalez-Andujar and Fernandez-Quintanilla, 1991, 1993). For short-spiked canarygrass most published work is on competition with cereals, while studies on its demography and population dynamics are very scant (Jimenez-Hidalgo et al., 1990). The objectives of this study were (1) to estimate the annual rates of seedling recruitment, plant survival and plant fecundity for P. brachystachys and (2) to determine the population growth rate (l) of this species and its sensitivity to life history parameters.
ARTICLE IN PRESS 582
J.L. Gonzalez-Andujar et al. / Crop Protection 24 (2005) 581–584
2. Material and methods Experiments were conducted in a farm field at Trinidades (Cordoba, South Spain) with no previous infestation of P. brachystachys, on a vertisol soil with a pH of 8.4. Average annual rainfall in the studied area is 600 mm seasonally distributed in autumn and spring. The study was carried out during three consecutive seasons, 1988–90 during a wheat–sunflower rotation, although only in the wheat years the P. brachystachys demography can be estimated (1988 and 1990). The elemental plot was 3 6 m with three permanent replications. Each November in the wheat year, the plots were sown to winter wheat (cv. ‘Anza’ at 180/ 220 kg h1) and harvested in June. No herbicide was used to control short-spiked canarygrass. In the experiments 1150 seeds (64 seeds m2) of P. brachystachys were broadcast on the soil surface of each plot and immediately incorporated (o10 cm depth) with a field cultivator. Within each plot seedlings m2 was determined between January and March by sampling at 10 random quadrats (0.1 m2) per plot. Emergence of P. brachystachys take place predominantly in late autumn and early winter. Immediately before crop harvest, the number of plants m2 and the panicle m2 were determined by sampling at random 8 quadrat of 0.25 m2 per plot. The number of seed per panicle was determined averaging a random sample of about 80 panicles.
3. Results and discussion 3.1. Seeding recruitment The average emergence was 16.70 seedlings m2 (SE ¼ 14:78). Similar results had been obtained by Amor (1985) with Australian populations under Mediterranean climate. Other authors (Okereke et al., 1981; Yaduraju et al., 1984) found higher emergence rates, however such results were obtained under glasshouse conditions. The rate of seedling recruitment, pg, was established as the proportion of the seed bank that emerged throughout the growing season (Mortimer et al., 1980). The average rate was 0.18 (SE ¼ 0:08). 3.2. Seedling survivorship Seedling survival was not very high and relatively uniform. The rate of plant survivorship, ps, was calculated as the probability of emerged seedlings surviving to set seed. Seedling survivorship was estimated with an average value of 0.30 (SE ¼ 0:05). Some authors have reported self-regulation through densitydependent processes (e.g. Gonzalez-Andujar and
Fernandez-Quintanilla, 1991). We did not detect such processes, perhaps because they may occur only at higher density infestations. 3.3. Adult fecundity Plant fecundity, f, was calculated as the product of panicles plant1 and seeds panicle1. The panicle number was relatively stable with an average value of 6.26 (SE ¼ 1:02) panicles plant1. The average number of seeds panicle1 was 196.8 (SE ¼ 21:59). Afentouli and Eleftherohorinos (1996) reported 190 seeds panicle1 for short-spiked Canarygrass, very close to our results. Average fecundity was estimated at 1232 seeds adult plant1(SE ¼ 464:90). Total seed production per square metre (seed rain) was 5392 in 1988 and 25,101 in 1990.
4. Population dynamics The annual dynamics of the population was described using a life-cycle diagram, following the approach of Fernandez-Quintanilla et al. (1986). According to this approach, the life cycle of the plant was divided into four different functional phases: seedlings, mature plants, seed produced and seed bank (Fig. 1). All these phases were interconnected through five interphases: seedling recruitment, plant survivorship, fecundity, seed rain recruitment, seed survivorship in soil (Fig. 1). The experimental results obtained indicate that the growth of the population during the plant ‘‘phase’’ was determined by low rate of seedling emergence, low seedling survivorship and high adult fecundity. In order to estimate the overall population growth ðlÞ; we used the basic model l ¼ ð1 pg Þð1 pm Þ þ pg ps ð1 pl Þ f ,
(1)
where pg is the probability of emergence, ps is portion of emerged seedlings that survive until reproduction (seedling survival), f is the number of viable seeds produced by mature plants (fecundity), pl is the portion of all the new seeds produced that are lost (e.g. predation) and pm is the portion of seeds that are removed by natural mortality (seed mortality). As our study only covered the quantification of pg, ps and f, estimates of the two remaining parameters (pm ¼ 0:5; pl ¼ 0:34) were taken from other studies (JimenezHidalgo, 1993) Using model (1) with the values obtained in this work, it was possible to estimate annual rate of population growth. The growth rate obtained was very high (l ¼ 75:96), indicating the potential of P. brachystachys to rapidly increase its populations in the absence of control measures. The high rate of potential population growth is mainly derived from the fecundity parameter.
ARTICLE IN PRESS J.L. Gonzalez-Andujar et al. / Crop Protection 24 (2005) 581–584
583
Table 1 Demography sensitivity analysis
Seed produced
Parameter Emergence Seedbank mortality Fecundity (seeds plant1) Seedling survivorship Seed losses
f (1232) Plants
Value pg pm f ps pl
243.43 0.82 0.03 146.36 66.52
ps (0.30) pl (0.34) Seedlings
pg (0.18) Seed Bank Pm (0.5)
Fig. 1. Life-cycle of P. brachystachys in winter wheat.
In the model described previously all the parameters are assumed to be constant. In practice most of these parameters vary from year to year. To examine the sensitivity of l we need to evaluate the partial derivative of l with respect to the life history parameters (Schmidt and Lawlor, 1983). The partial derivatives for parameters are @l=@pg ¼ ps ð1 pl Þf ð1 þ pm Þ, @l=@pm ¼ 1 þ pg , @l=@f ¼ pg ps ð1 pl Þ, @l=@ps ¼ pg ð1 pl Þf , @l=@pl ¼ pg ps f . The effects of changing the values of the different parameters were generally high, indicating a high sensitivity of the model to parameter variation (Table 1). Emergence, survivorship and seed losses were most sensitive to parameter variation. It is critical, therefore, that these three parameters must be estimated with maximum precision. However, reduction in fecundity and seed bank mortality did not have much influence. The high sensitivity values estimated for these three processes suggest that using management practices that reduce, germination, survivorship or increase seed loss may result in substantial reductions in weed populations.
Acknowledgements We are greatly indebted to The Spanish Ministry of Education and Science (R+D project AGL 2002-3801) for financial support.
References Afentouli, C.G., Eleftherohorinos, I.G., 1996. Littleseed canarygrass (Phalaris minor) and short-spiked canarygrass (Phalaris brachystachys) interference in wheat and barley. Weed Sci. 44, 560–565. Afentouli, C.G., Eleftherohorinos, I.G., 1999. Competition between wheat and canarygrass biotypes and their response to herbicides. Weed Sci. 47, 55–61. Amor, R.L., 1985. Seasonal emergence of weeds typically occurring in the Victorian cereal belt. Plant Prot. Quart. 1, 18–20. Bell, C.E., 1992. Littleseed canarygrass control in cereal grains. Res. Prog. Rep. West Soc. Weed Sci., 232–233. Bir, S.S., Sidhu, M., 1979. Observations on the weed flora of cultivable lanas in Punjab-wheat fields in Patiala District. New Bot. 6, 79–89. Catizione, P., Viggiani, P., 1980. Un quadriennio di ricerche sulle falaridi infestanti il grano. Atti Giornate Fitopatologiche (Supplemento no. 3), 257–311. Cudney, D.W., Hill, J.E., 1979. The response of wheat grown with three population level of canarygrass to various herbicide treatments. Proc. West. Soc. Weed Sci. 32, 55–56. Fernandez-Quintanilla, C., Navarrete, L., Gonzalez-Andujar, J.L., Fernandez, A., Sanchez, M.J., 1986. Seedling recruitment and agespecific survivorship and reproduction in populations of Avena sterilis ssp. ludoviciana. J. Appl. Ecol. 23, 945–955. Godinho, I., Costa, J.C.A., 1981. Concorrencia da Phalaris minor Retz. na cultura trigo. I Congresso Portugue´s de Fitiatria e de Fitofarmacologia e III Symposium Nacional de Herbologia, 1980, Vol. 3, pp. 237–243. Gonzalez-Andujar, J.L., Fernandez-Quintanilla, C., 1991. Modeling the population dynamics of Avena sterilis under dry-land cereal cropping systems. J. Appl. Ecol. 28, 16–27. Gonzalez-Andujar, J.L., Fernandez-Quintanilla, C., 1993. Strategies for the control of Avena sterilis in winter wheat production systems in central Spain. Crop Prot. 12, 617–623. Gonzalez-Andujar, J.L., Saavedra, M., 2003. Spatial distribution of annual grass weed populations in winter cereals. Crop Prot. 22, 629–633. Jimenez-Hidalgo, M.J., 1993. Incidencia y evolucio´n de los alpistes (Phalaris ssp.) en el trigo (Triticum sp.). Ph.D. Thesis. Universidad de Co´rdoba, Cordoba, Spain 162pp. Jimenez-Hidalgo, M.J., Saavedra, M., Garcia-Torres, L., 1990. Nota sobre la dina´mica de poblaciones de Phalaris brachystachys. In: Congreso 1990 de la Sociedad Espan˜ola de Malherbologia, Madrid, Spain, pp. 299–306.
ARTICLE IN PRESS 584
J.L. Gonzalez-Andujar et al. / Crop Protection 24 (2005) 581–584
Jimenez-Hidalgo, M.J., Saavedra, M., Garcia-Torres, L., 1997. Phalaris brachystachys en cultivos de cereales. In: Sans, X., Fernandez-Quintanilla, C. (Eds.), Biologı´ a de las Malas Hierbas de Espan˜a. Phytoma Espan˜a, Valencia, Spain, pp. 77–89. Okereke, O.U., Blari, A.M., Caseley, J.C., 1981. Effects of depth of planting, temperature and soil moisture on seed emergence and survival in soil of Bromus sterilis and Phalaris minor. In: Proceedings of the Conference on Grass Weeds in Cereals, UK.
Schmidt, K.P., Lawlor, L.R., 1983. Growth rate projection and life history sensitivity for annual plants with seed bank. Am. Nat. 121, 525–539. Yaduraju, N.T., Caseley, J.C., Drennan, D.S.H., 1984. Some studies on germination, emergence and growth of Phalaris minor Retz and P. paradoxa L. In: Proceedings of EWRS Third Symposium on Weed Problems in the Mediterranean Area, pp. 447–454.