90 research outputs found
Rhamphicarpa fistulosa, a widespread facultative hemi-parasitic weed, threatening rice production in Africa
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 (0β2150 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 mβ2 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
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Host interactions, pathology, economic impacts and management of the facultative parasitic weed Rhamphicarpa fistulosa
Rhamphicarpa fistulosa (Hochst.) Benth., is a facultative parasitic plant causing persistent weed problems in smallholder rice crops across Africa. It was first identified as a rice weed in the 1990's in West Africa. The objective of this review was to comprehensively inform the crop protection research community and extension services on the newly gained insights on R. fistulosa since the last review in 2014. Following a systematic literature search in Web of Science on papers published after September 2014, the cut-off date of the last review, the resulting publications are reviewed. Parasitizing Rhamphicarpa fistulosa plants gain considerably in biomass and reproductive output, compared to independently growing plants. The host incurs severe reductions in photosynthetic efficiency and biomass production. Host-plant assimilates primarily benefit parasite growth and reproduction. Rice yield losses caused by R. fistulosa infestations range from 24 to 73% depending on infestation density and cultivar. Annual crop losses in sub-Saharan Africa were estimated at 204,000 tons of milled rice, with associated annual economic losses of US $82M, affecting >140,000 rural households. Rice cultivars NERICA-L-40 and -31 were identified as resistant and high yielding under R. fistulosa infested conditions. Early sowing decreases R. fistulosa infection. Contrary to the obligate parasitic weed Striga spp., the facultative R. fistulosa is not controlled by fertilisers. The past decade of research generated valuable insights in the genetics, germination biology, environmental and ecological contexts, distribution and impacts on crop yields and economies, and disclosed feasible management options
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Differences in the ecology of witchweed and vampireweed: implications for rice farming in Africa
Parasitic weeds in African rice systems affect household-level food security and income generation in Africa. Most affected farmers are smallholders with limited weed management capacities, crop production infrastructure and resources. The facultative parasite Rhamphicarpa fistulosa (rice vampireweed) has become a major problem in rainfed lowland rice whereas the obligate parasites Striga asiatica and S. hermonthica(witchweed) are problematic in rainfed upland rice. Striga asiatica, S. hermonthica and Rhamphicarpa fistulosaare all root hemiparasitic plants from the same family, Orobanchaceae, with similar distribution and host-plant effects. The differences in biology (facultative vs obligate parasitism) and ecology (lowland vs upland) between these weed species appear more important than their similarities regarding the effectiveness of management strategies in rice production systems
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Lessons on enabling African smallholder farmers, especially women and youth, to benefit from sustainable agricultural intensification
The papers in this Special Issue on what works and what is unlikely to work to enable poorer smallholders, especially women and youth, to benefit from Sustainable Agricultural Intensification (SAI) come from the Sustainable Agricultural Intensification Research and Learning programme. Three aspects of SAI are considered: (1) the equity of outcomes from SAI and how decisions to support equity can be better informed; (2) the social, economic and environmental trade-offs associated with SAI, how they are perceived and can be managed; and (3) how farmers access to services and information needed to implement SAI can be facilitated. Whether considering the gender and generational equities of participation in SAI or how trade-offs limit adoption of SAI, it is the local social, economic and environmental conditions that determine the outcome. We conclude that participation of local stakeholders in the adaptation of SAI to local social, economic and environmental conditions is critical to enabling poorer smallholders, women and youth to benefit from SAI. While some tools and processes are presented that may support this, there remains a challenge as to how such processes can be integrated into national policies and institutions
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