Rhamphicarpa fistulosa, a widespread facultative hemi-parasitic weed, threatening rice production in Africa
Rodenburg, J. ; Morawetz, J.J. ; Bastiaans, L. - \ 2015
Weed Research 55 (2015). - ISSN 0043-1737 - p. 118 - 131.
sub-saharan africa - fed lowland rice - phylogenetic-relationships - rhinanthus-minor - scrophulariaceae - vegetation - orobanchaceae - management - haustoria - habitats
Rhamphicarpa fistulosa is a facultative hemi-parasitic plant of the Orobanchaceae family, adapted to wet soils. Apart from tropical Australia, it is only found in sub-Saharan Africa, where it is considered a minor weed in cereal crops such as rice. Due to this status, the species has received only sporadic attention. Recent field observations and encounters with rice farmers in several African countries showed that R. fistulosa is, however, a more serious and increasing production constraint than previously thought. Results from a systematic literature review and a global herbarium study support this. The species has a broad distribution over Africa (at least 35 countries from Madagascar to Senegal and from Sudan to South Africa) and a wide range in altitude (0–2150 m a.s.l.) and environment (waterlogged swamps to moist free-draining uplands). Rhamphicarpa fistulosa is relatively independent and persistent because of the presumably wide host range, the facultative nature of its parasitism and its prolific seed (estimated 100 000 seeds m-2 under moderate infestation levels). Finally, R. fistulosa causes severe yield losses (average 60%) and high regional annual economic losses (estimated US $175 million), while effective control options are scant and awareness of the species among important R&D stakeholders is almost absent. An integrated approach is advocated to assist the rice sector to reduce current R. fistulosa-inflicted losses and to prevent further spread of the species into new areas.
Can the parasitic weeds Striga asiatica and Rhamphicarpa fistulosa co-occur in rain-fed rice?
Kabiri, S. ; Rodenburg, J. ; Kayeke, J. ; Ast, A. van; Makokha, D.W. ; Msangi, S.H. ; Irakiza, R. ; Bastiaans, L. - \ 2015
Weed Research 55 (2015)2. - ISSN 0043-1737 - p. 145 - 154.
management - africa - scrophulariaceae - ecology - systems - growth
Striga asiatica and Rhamphicarpa fistulosa are important parasitic weeds of rain-fed rice, partly distributed in similar regions in sub-Saharan Africa (SSA). It is not evident whether their ecologies are mutually exclusive or partially overlapping. In Kyela, a rice-growing area in south Tanzania where both parasites are present, three transects of about 3 km each across the upland–lowland continuum were surveyed in June 2012 and 2013. A total of 36 fields were categorised according to their position on the upland–lowland continuum as High, Middle or Low and soil samples were taken. In each field, parasitic and non-parasitic weed species were identified in three quadrats. Additionally, in two pot experiments with four different moisture levels ranging from wilting point to saturation, influence of soil moisture on emergence and growth of parasites was investigated. Striga asiatica was observed in higher lying drier fields, while R. fistulosa was observed in the lower lying wetter fields. Furthermore, non-parasitic weed species that were exclusive to S. asiatica-infested fields are adapted to open well-drained soils, while species that were exclusive to R. fistulosa fields are typical for wet soils. The experiments confirmed that S. asiatica is favoured by free-draining soils and R. fistulosa by waterlogged soils. These results imply that changes in climate, specifically moisture regimes, will be crucial for future prevalence of these parasitic weeds. The non-overlapping ecological range between their habitats suggests that their distribution and associated problems might remain separate. Thus, management strategies can be focused independently on either species.
Determinants of parasitic weed infestation in rainfed lowland rice in Benin
N'cho, A.S. ; Mourits, M.C.M. ; Rodenburg, J. ; Demont, M. ; Oude Lansink, A.G.J.M. - \ 2014
Agricultural Systems 130 (2014). - ISSN 0308-521X - p. 105 - 115.
sub-saharan africa - rhamphicarpa-fistulosa - striga-hermonthica - farming systems - management - selection - scrophulariaceae - specification - demand - model
The parasitic weed Rhamphicarpa fistulosa is threatening rainfed lowland rice production in Benin. The aim of this study was to explore factors (such as biophysical characters of the rice growing environment, farmers’ management practices, and socioeconomic characteristics) that affect the infestation of rainfed lowland rice fields by R. fistulosa and farmers’ ability to cope with the problem. Data were collected from 231 rice plots located in 12 inland valleys infested by Rhamphicarpa in Benin. Data were analyzed using a double hurdle model, which analyses both the likelihood (of occurrence) and the severity of infestation. Results showed that 72% of the surveyed rice plots were infested by R. fistulosa and the average severity was 109 plants m-2. The likelihood of infestation was higher on poorly fertile soils and fields located in the inland-valley bottom, and it decreases through timely use of herbicides and ploughing. Severity of infestation was higher on rice plots cultivated by female-headed households farmers and reduced through management practices such as late sowing, timely application of post-emergence herbicide, three hoe or hand weeding operations, medium-rate fertilizer application and prolonged fallow. Likelihood and severity of infestation were found to be negatively correlated. These findings suggest that farmers can reduce the likelihood and the severity of infestation of their plot as long as they are aware of factors causing the problem given their access to and management capacity of production resources.
Long-term management of Striga hermonthica: strategy evaluation with a spatio-temporal population model
Mourik, T.A. van; Bianchi, F.J.J.A. ; Werf, W. van der; Stomph, T.J. - \ 2008
Weed Research 48 (2008)4. - ISSN 0043-1737 - p. 329 - 339.
control technologies - northern nigeria - weed - scrophulariaceae - dynamics - mali - constraints - farmers - seeds - yield
The parasitic weed Striga hermonthica poses a serious threat to cereal production in sub-Saharan Africa. Striga hermonthica seedbanks are long-lived; therefore, long-term effects of control strategies on the seedbank only emerge after several years. We developed a spatially explicit, stochastic model to study the effectiveness of control strategies in preventing invasion of S. hermonthica into previously uninfested fields and in reducing established infestations. Spatial expansion of S. hermonthica and decrease in millet yield in a field was slower, on average, when stochasticity of attachment of seedlings to the host was included and compared to the deterministic model. The spatial patterns of emerged S. hermonthica plants 4¿7 years after point inoculation (e.g. seeds in a dung patch) in the spatial-stochastic model resembled the distribution typically observed in farmers' fields. Sensitivity analysis showed that only three out of eight life cycle parameters were of minor importance for seedbank dynamics and millet yield. Weeding and intercropping millet with sesame or cowpea reduced the seedbank in the long term, but rotations of millet with trap crops did not. High seedbank replenishment during years of millet monoculture was not sufficiently offset by seedbank depletion in years of trap crop cultivation. Insight from simulations can be employed in a participatory learning context with farmers to have an impact on S. hermonthica control in practice
Long-term management of the parasitic weed Striga hermonthica : strategy evaluation with a population model
Westerman, P.R. ; Ast, A. van; Stomph, T.J. ; Werf, W. van der - \ 2007
Crop Protection 26 (2007)3. - ISSN 0261-2194 - p. 219 - 227.
seed-germination - crop-rotation - sorghum - scrophulariaceae - infestation - dynamics - mali
To increase sorghum yields in areas in Africa that are heavily infested with the root parasite Striga hermonthica, crop varieties are being bred whose roots emit fewer exudates that stimulate S. hermonthica seeds to germinate. Because S. hermonthica has a persistent seedbank, it is important to anticipate the long-term effects of such breeding efforts on the seedbank dynamics. This study reports the results of analyses conducted with a population model for S. hermonthica based on existing and earlier published models and data. The essential innovation is an explicit modelling of density-dependent feedback, which was included at different points in the life cycle. Sensitivity analyses showed that density-dependence reduced the impact on the equilibrium seedbank density of life cycle parameters at stages preceding the density-dependent process. The implication is that intervention early in the parasite life cycle through, for instance, breeding for low exudate emission of the cereal host, carries the risks of maintaining or increasing S. hermonthica seedbanks, and selection for S. hermonthica populations responsive to the new varieties. Only crop varieties with very low production of germination-stimulant will be effective in the long run. The best breeding strategy is to select for crop varieties that inhibit S. hermonthica development or growth at stages later in the life cycle or that affect the parasite at multiple stages simultaneously. The most effective management strategy is to use control measures that cause a reduction in seed production, viability of newly produced seed, or seed survival in the soil, or to use a combination of measures that affect the parasites at multiple stages. Despite considerable knowledge gaps regarding the basic demography of S. hermonthica, the model proved useful in identifying points in the S. hermonthica life cycle that are of particular interest for designing intervention strategies. In-depth studies on the demography of S. hermonthica and on the location(s) of density-dependence in the parasite's life cycle are needed.
Dormancy and germination of six Rhinanthus species in relation to climate
Borg, S.J. ter - \ 2005
Folia Geobotanica 40 (2005)2/3. - ISSN 1211-9520 - p. 243 - 260.
chalk-grassland - scrophulariaceae - seed - demography - ecology
The genus Rhinanthus (Orobanchaceae) consists of annual hemiparasites that occur in a wide range of climates. Patterns of dormancy and germination were studied for six species sampled in areas ranging from the Pyrenees to Northern Scandinavia, and from sea level up to about 2500 m altitude in the Alpine region. Dormancy was broken by a 2 to 6 months period of cold stratification. Optimal temperature and length of the stratification period appeared to vary between and within species. Two patterns of dormancy and germination were distinguished. Seeds of the first group, including the widely distributed R. minor and R. angustifolius, further referred to as the LW group, require a relatively long period of cold stratification. Moreover, their germination is accelerated if they are subjected to a widening range of higher temperatures in the last weeks of the stratification period. In the other species (R. alectorolophus, R. glacialis, R. mediterraneus and perhaps R. antiquus) the release of dormancy is completed in a rather short period. Higher temperatures in the last weeks of the stratification period hardly affect the germination process of this SN-group, with short dormancy and no accelerated germination at higher temperatures. In both groups, temperatures above the low values during stratification reduce germination percentages and induce secondary dormancy in non-germinated seeds. The effects strongly vary with timing and temperature. The patterns have a genetic basis and seem to be species-specific. They do not vary with climate conditions, since samples R. minor, whether collected in sub-arctic or sub-alpine areas or at sea level, generally react according to the LW pattern, and samples of R. alectorolophus from areas at sea level up to montane regions according to the SN one. The ecological significance of the various stratification requirements and effects of higher temperatures on germination is discussed in relation to the local climate of the species and the evolutionary history of the genus.
Teeltonderzoek Digitalis lanata 1987 - 1994 = Crop research on Digitalis lanata 1987 - 1994
Mheen, H.J. van der - \ 1996
Lelystad : PAGV (Verslag / Proefstation voor de Akkerbouw en de Groenteteelt in de Vollegrond nr. 218) - 80
chemische bestrijding - teelt - cultuurmethoden - kunstmeststoffen - experimenteel veldonderzoek - mest - medicinale planten - plantenvoeding - gewasbescherming - scrophulariaceae - chemical control - cultivation - cultural methods - fertilizers - field experimentation - manures - medicinal plants - plant nutrition - plant protection - scrophulariaceae
Liggende ereprijs (Veronica prostrata L.) in de Vreugderijkerwaard
Ploeg, N. van der - \ 1994
Gorteria 20 (1994). - ISSN 0017-2294 - p. 41 - 47.
scrophulariaceae - overijssel - scrophulariaceae - overijssel
Najaarsteelt van leeuwebek (Antirrhinum)
Krogt, T.M. van der - \ 1982
Aalsmeer : Proefstation voor de Bloemisterij in Nederland (Rapport / Proefstation voor de Bloemisterij in Nederland no. 11) - 14
nederland - sierplanten - scrophulariaceae - herfstteelt - netherlands - ornamental plants - scrophulariaceae - autumn cultivation
Een sortiment handelsrassen dat ook in de voorjaarsteelt gebruikt wordt, is getoetst op de gebruiksmogelijkheden in het najaar. Met enkele kultivars is een temperatuurproef gedaan. In de twee daaropvolgende jaren is een gekombineerde zaaitijden-rassenproef genomen, waarbij gebruik werd gemaakt van de beschikbare sortimentsgegevens. De resultaten uit bovengenoemd onderzoek worden beschreven, waarnaast tevens aandacht wordt besteed aan de sortimentsopplanting in het najaar 1979; de invloed van de temperatuur op de ontwikkeling in het najaar en de zaaitijden en het sortiment in najaar 1980 en 1981
Some recent observations on Digitalis purpurea L. f. heptandra De Chamisso
Wassink, E.C. - \ 1972
Wageningen : Veenman (Mededelingen Landbouwhogeschool Wageningen 72-22)
scrophulariaceae - scrophulariaceae