Can the parasitic weeds Striga asiatica and Rhamphicarpa fistulosa co‐occur in rain‐fed rice?

Abstract

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 uplandlowland 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 investi-gated. 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 nonoverlapping 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.

Participatory appraisal of institutional and political constraints and opportunities for innovation to address parasitic weeds in rice

“…They demonstrated that the adoption of control or prevention strategies for parasitic weeds is strongly correlated with farmers' access to credit, information and training; the same constraints that were prioritised by stakeholders in this study. Additionally, there is broad-based evidence showing that parasitic weed problems are a direct consequence of poor soil fertility (Kabiri et al, 2015;Parker, 2009), which directly relates to constraints such as untimely access to high quality inputs identified in this study. Following Klerkx et al (2012), addressing such generic constraints is likely to have a spillover effect on dealing with complex agricultural problems other than parasitic weeds.…”

“…Land tenure agreements, for instance, were not explicitly singled-out as a constraint while they form an institutional dimension related to parasitic weed problems. Parasitic weeds are particularly problematic on land characterised by poor soil fertility and water management (Kabiri et al, 2015). Such marginal land is often allocated to socio-economically disadvantaged groups such as women.…”

Systems approaches to innovation in pest management: reflections and lessons learned from an integrated research program on parasitic weeds in rice

“…Combined with knowledge on the environmental preferences of each weed, obtained from project 1 (e.g. Kabiri et al 2015), and figures obtained on their appearance, frequency, infestation rates, yield losses and the socio-economic factors affecting these variables obtained from project 3 (e.g. N'cho 2014), we can estimate a stochastic impact of parasitic weeds on rice production, using a diverse set of modeling techniques.…”

“…The likelihood of infestation by R. fistulosa is higher on poorly fertile soils and fields located in the valley bottom and it is reduced through management practices such as late sowing and the application of medium-rate fertilizer (N'cho, Mourits, . Based on pot experiments combined with field measurements and observations, Kabiri et al (2015) concluded that the valley bottoms are the preferred habitat for R. fistulosa and that the soils in these valley bottoms can be characterized as poor in terms of fertility. An earlier study based on pot experiments, by Rodenburg et al (2011), showed that R. fistulosa can indeed be reduced by the application of inorganic fertilizers leading to increased (chemical) soil fertility.…”

Effets de traitements herbicides sur <i>Rhamphicarpa fistulosa</i> (Hochst.) Benth. Une plante parasite facultative

“…Ceci se rapportant essentiellement sur l'écologie. D'autres informations sur la biologie ont été données aussi par Ouédraogo et al (1999), Jones et al 1994, Kabiri et al (2015. La capacité de production de graines des phanérogames parasite est énorme.…”