Papers by Alain Ratnadass
International Journal of Pest Management, 2015
XXVIII International Horticultural Congress on Science and Horticulture for People (IHC2010): International Symposium on Horticulture for Development, 2011
... Actually the whole Omega3 project could have been built on horticultural case studies alone, ... more ... Actually the whole Omega3 project could have been built on horticultural case studies alone, since several vegetable crops are grown under DMC ... but manual control of the pest is difficult to achieve due to panicle compactness of the crop, and its attractiveness period which is ...
XXVIII International Horticultural Congress on Science and Horticulture for People (IHC2010): International Symposium on Plant Protection, 2011
Introduction Sorghum [Sorghum bicolor (L.) Moench] is the m a i n cereal crop in B u r k i n a Fa... more Introduction Sorghum [Sorghum bicolor (L.) Moench] is the m a i n cereal crop in B u r k i n a Faso w i t h mean annual cultivated area and grain production of 1.3 m i l l i o n ha and 0.943 m i l l i o n tons, respectively ( F A O 1999). The crop is subject to various abiotic and biotic constraints. A m o n g the latter, insect pests are of major importance. They m a i n l y belong to t w o groups: lepidopterous stem borers [Busseola fusca (Fuller), Sesamia calamistis (Hampson), Coniesta ignefusalis (Hampson), Eldana saccharinal (Walker) and Chilo diffusilineus (de Joannis)] and panicle-feeding insects | sorghum midge (Stenodiplosis sorghicola Coquillett) and head bugs (particulary Eurystylus oldi Poppius)] ( D a k o u o and Lankoande 1992). Y i e l d losses due to stem borers range f r o m 16 to 3 2 % under research station conditions in the absence of protection measures ( D a k o u o and Lankoande 1992). Earlier studies carried out by D a k o u o and Ratnadass (1997) revealed that B. fusca was the dominant species at Farako-ba research station, near Bobo-Dioulasso in the southwestern part of B u r k i n a Faso. D a k o u o and Ratnadass (1997) developed for B. fusca a m o n i t o r i n g method based on a pheromone-baited trap, w h i c h was f o u n d effective on research station. The trapping system was subsequently tested in farmers' fields during t w o consecutive wet seasons in 1998 and 1999 to m o n i t o r the distribution and importance of the pest both on research station and in farmers' fields. The present paper reports the m a i n results obtained. Pheromone t r a p materials. The trap design was chosen according to previous studies ( Y o u m and B e e v o r 1995; Dakouo and Ratnadass 1997). It consisted of an a l u m i n i u m tray (35.5-cm diameter) f i l l e d to a depth of 2 cm w i t h water to w h i c h a few drops of l i q u i d detergent had been added. The tray was supported 0.5 m above g r o u n d level. A shade consisting of a second a l u m i n i u m tray (26.5-cm diameter) was suspended 5 cm above the larger tray f r o m a horizontal wooden support; both trays were secured w i t h wires. A polythene vial dispenser containing the synthetic pheromone blend of B. fusca (commercially available f r o m AgriSense-BCS, U K ) was suspended f r o m the underside of the shade on small w i r e . E x p e r i m e n t a l design and t r a p p i n g method. There were seven trapping sites d u r i n g the t w o years. Six sites were located in farmers' sorghum fields at Darsalamy, Sisalia, Samangan, Bankeledaga, Sakaby, and Tondogosso, all w i t h i n a radius of 5 to 25 km f r o m the site located on the Farako-ba research station. M o t h catches were sorted, removed, and recorded daily at the research station, and three times a week in farmer's fields (in the latter sites by the farmers w h o had been trained prior to the experiment). Pheromone traps operated f r o m M a y to December corresponding to the wet season.
I International Symposium on Tropical Horticulture, 2011
African journal of agricultural research
Okra (Abelmoschus spp.) is a traditional vegetable crop with considerable area under cultivation ... more Okra (Abelmoschus spp.) is a traditional vegetable crop with considerable area under cultivation in Africa and Asia with huge socio-economic potential in West and Central Africa. It has been called "a perfect villager's vegetable" because of its robust nature, dietary fibers and distinct seed protein balanced in both lysine and tryptophan amino acids (unlike the proteins of cereals and pulses) it provides. However, okra has been considered a minor crop and no attention was paid to its improvement in the international research program in past. This review describes a general overview of okra's nutritional and economic potential with special reference to its past and recent progress on germplasm regeneration, genetic studies and efforts on genetic improvement in West and Central Africa.
ABSTRACT Farmers in the tropics are faced with crop protection issues such as adverse impacts of ... more ABSTRACT Farmers in the tropics are faced with crop protection issues such as adverse impacts of pesticides on human health and on the environment, particularly in intensive agrosystems in French overseas islands, or food insecurity and low income due to pest-induced crop losses, particularly in low-input traditional systems in Sub-Saharan Africa. A Cirad-funded " Omega3 " project tackles these problems by studying the effects of the planned introduction of plant species diversity (PSD) in tropical agrosystems, as a potential alternative to conventional practices based on pesticide use. One of the several study cases the project focused on is the use of sweet corn as a trap crop to control the populations and damages of Helicoverpa zea in tomato field in the French West Indies (Martinique). To understand system functioning and improve H. zea management, we are developing a spatially-explicit individual-based model at the field scale. The model comprises 3 interacting modules that describe (i) phenology of tomato and corn plants and dynamic of the attractive plant stages for H. zea (ii) H. zea development, both using thermal units, and (iii) H. zea movement and oviposition behavior. More widely, we aim to use this model as a generic tool to improve our understanding of what make the use of a trap crop successful in managing pests among the insect behavioural traits, the crop traits (e.g., relative attractiveness) and the spatio-temporal planting design of the trap and commercial crops. The modeling approach we are currently developing and further issues are presented.
Journal of Phytopathology, 2014
Ralstonia solanacearum is responsible for bacterial wilt affecting many crops worldwide. The emer... more Ralstonia solanacearum is responsible for bacterial wilt affecting many crops worldwide. The emergent population of R. solanacearum (phylotype IIB/ 4NPB) wilts previously resistant varieties and has rapidly spread throughout Martinique. No conventional method is known to control it. In this study, previous crops used as sanitizing crops were investigated as an environmentally safe alternative method of control. The ability of the emergent population of R. solanacearum to persist in planta and in the rhizosphere of Brassicaceae, Asteraceae and Fabaceae grown as previous crops was evaluated in controlled conditions, and the incidence of bacterial wilt was assessed in the following tomato crop. Results showed that all species carried R. solanacearum latently. Among Brassicaceae and Asteraceae, the highest density of R. solanacearum was found in planta and in the rhizosphere of Tagetes erecta. The density of the R. solanacearum population in the rhizosphere of Raphanus sativus cv. Karacter was significantly higher than that in Raphanus sativus cv. Melody. In Fabaceae, the density of R. solanacearum population in planta was statistically similar in all species. The density of the R. solanacearum population in the rhizosphere of Crotalaria juncea was significantly higher than that in Crotalaria spectabilis. This study showed for the first time that Crotalaria spectabilis and Raphanus sativus cv. Melody grown as previous crops improve the performance of the following tomato with similar effects on R. solanacearum populations in the soil as bare soil. The incidence of the disease in tomato decreased by 86% and 60%, after R. sativus cv. Melody and C. spectabilis, respectively, and the proportion of infected plants also decreased. These results suggest that C. spectabilis and R. sativus cv. Melody can be used as previous crops to help bacterial wilt control in ecological management strategies without drastic suppression of R. solanacearum population in stem tissues and in the rhizosphere.
International Journal of Pest Management, 2014
ABSTRACT Trap cropping is an environmentally friendly “alternative” pest management strategy. To ... more ABSTRACT Trap cropping is an environmentally friendly “alternative” pest management strategy. To maximize the efficiency of corn, Zea mays L. (Poaceae), as a trap crop for Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), we (i) tested the trap crop potential of corn varieties that are not a source of infestation, and (ii) determined the best corn planting time so as to concentrate H. zea in this trap crop and divert the pest from tomato, Solanum lycopersicum L. (Solanaceae). When corn silk emergence was synchronized with tomato flowering and fresh corn silk was present during the tomato flowering stage, H. zea infestation was lower in the tomato field with a corn border than in those without a corn border. Sugar Jean and Java corn varieties were good trap crops because few larvae persisted on the silks and their growth was low. These two varieties could reduce the risk of H. zea development and dispersion from corn borders.
Sustainable Agriculture Reviews, 2014
ABSTRACT We need to break away from intensive agriculture based on non-renewable and toxic inputs... more ABSTRACT We need to break away from intensive agriculture based on non-renewable and toxic inputs. Safer practices are indeed emerging. Sustainable agriculture started about 50 years ago with the design of integrated pest management (IPM) to counteract pesticide misuse and abuse. Ecological intensification emerged only a few years ago. Here we review the literature to compare ecological intensification and IPM, from the point of view of crop protection. We present also agroecology and organic farming. Neither ecological intensification nor IPM have philosophical bases such as agroecology, or to an even larger extent, biodynamic agriculture. Ecological intensification, IPM and agroecology are polysemous, flexible and pragmatic approaches, whereas organic farming is well-defined by its scope and standards. Ecological intensification, in explicitly pursuing the goal of increasing food production to feed the planet, differs from agroecology, whose proponents think that the view that world hunger will be solved by merely increasing yield is an oversimplification. In terms of cropping system design, in its actual practice, IPM often remains based on methods that increase the efficiency of chemical pesticide use. Or, along with organic agriculture, it may remain based on substitution of pesticides by less harmful alternatives. In contrast, ecologically intensive crop protection usually requires cropping system redesign. In terms of ecosystem service provision, IPM tends to focus on the pest-pathogen regulation service. In contrast, both ecological intensification and agroecology pay attention to both practices which were designed for crop protection and biomass provision purposes, as well as practices with broader scope, primarily designed to offer other ecosystem services which are found to have indirect effects on crop protection. This chapter also describes selected tropical case studies of crop protection, such as upland rice seed-dressing and fruit fly control in orchards, to compare and contrast crop protection in these contexts. Finally, we propose to consider IPM and ecologically intensive crop protection as complementary rather than conflicting approaches. The concept of “ultimate IPM” brings IPM closer to ecologically intensive crop protection. This new approach involves starting from a nearly natural ecosystem to which inputs are gradually added when absolutely necessary, rather than starting from a conventional agroecosystem and gradually remove inputs from it.
International Journal of Molecular Sciences, 2012
The physic nut shrub, Jatropha curcas (Euphorbiaceae), has been considered as a "miracle tree", p... more The physic nut shrub, Jatropha curcas (Euphorbiaceae), has been considered as a "miracle tree", particularly as a source of alternate fuel. Various extracts of the plant have been reported to have insecticidal/acaricidal or molluscicidal/anthelminthic activities on vectors of medical or veterinary interest or on agricultural or non-agricultural pests. Among those extracts, the phorbol ester fraction from seed oil has been reported as a promising candidate for use as a plant-derived protectant of a variety of crops, from a range of pre-harvest and post-harvest insect pests. However, such extracts have not been widely used, despite the "boom" in the development of the crop in the tropics during recent years, and societal concerns about overuse of systemic chemical pesticides. There are many potential explanations to such a lack of use of Jatropha insecticidal extracts. On the one hand, the application of extracts potentially harmful to human health on stored food grain, might not be relevant. The problem of decomposition of phorbol esters and other compounds toxic to crop pests in the field needing further evaluation before such extracts can be widely used, may also be a partial explanation. High variability of phorbol ester content and hence of insecticidal activity among physic nut cultivars/ecotypes may be another. Phytotoxicity to crops may be further limitation. Apparent obstacles to a wider application of such extracts are the costs and problems involved with registration and legal approval. On the other hand, more studies should be conducted on molluscicidal activity on slugs and land snails which are major pests of crops, particularly in conservation agriculture systems. Further evaluation of toxicity to natural enemies of insect pests and studies on other beneficial insects such as pollinators are also needed.
Agronomy For Sustainable Development, 2012
Farmers are facing serious plant protection issues and phytosanitary risks, in particular in the ... more Farmers are facing serious plant protection issues and phytosanitary risks, in particular in the tropics. Such issues are food insecurity, lower income in traditional lowinput agroecosystems, adverse effects of pesticide use on human health and on the environment in intensive systems and export restrictions due to strict regulations on quarantine pests and limits on pesticide residues. To provide more and better food to populations in both the southern and northern hemispheres in a sustainable manner, there is a need for a drastic reduction in pesticide use while keeping crop pest and disease damage under control. This can be achieved by breaking with industrial agriculture and using an agroecological approach, whose main pillar is the conservation or introduction of plant diversity in agroecosystems. Earlier literature suggest that increasing vegetational biodiversity in agroecosystems can reduce the impact of pests and diseases by the following mechanisms: (1) resource dilution and stimulo-deterrent diversion, disruption of the spatial cycle, (3) disruption of the temporal cycle, (4) allelopathy effects, (5) general and specific soil suppressiveness, (6) crop physiological resistance, (7) conservation of natural enemies and facilitation of their action against aerial pests and (8) direct and indirect architectural/ physical effects. Here we review the reported examples of such effects on a broad range of pathogens and pests, e.g. insects, mites, myriapods, nematodes, parasitic weeds, fungi, bacteria and viruses across different cropping systems. Our review confirms that it is not necessarily true that vegetational diversification reduces the incidence of pests and diseases. The ability of some pests and pathogens to use a wide range of plants as alternative hosts/reservoirs is the main limitation to the suppressive role of this strategy, but all other pathways identified for the control of pests and disease based on plant species diversity (PSD) also have certain limitations. Improving our understanding of the mechanisms involved should enable us to explain how, where and when exceptions to the above principle are likely to occur, with a view to developing sustainable agroecosystems based on enhanced ecological processes of pest and disease control by optimized vegetational diversification.
Agricultural and Forest Entomology, 2014
1 The potential of perimeter trap cropping, using short and extra-short duration pigeon pea (SD P... more 1 The potential of perimeter trap cropping, using short and extra-short duration pigeon pea (SD PP and ESD PP), sorghum and cotton, was evaluated in Niger as an agroecological alternative to pesticide application on okra for the management of the tomato fruit worm (TFW) Helicoverpa armigera (Hübner). 2 In 2008, infestation by TFW and damage by fruit worms of unsprayed okra with SD PP borders was intermediate between cypermethrin-sprayed and unsprayed pure okra crops. 3 In 2009, the cypermethrin-sprayed okra was significantly less damaged by fruit worms than in the unsprayed pure okra, as well as in the unsprayed okra crops with SD PP, sorghum and cotton borders. 4 In 2010, the pure okra crop sprayed with cypermethrin was significantly less infested by TFW than the unsprayed pure okra crop and the unsprayed okra crop with SD PP borders. The unsprayed okra crop with ESD PP borders was intermediate between cypermethrin-sprayed and unsprayed pure okra crops. 5 The slightly lower TFW infestation of the unsprayed okra crop with ESD PP borders was a result of increased top-down regulation by predator spiders, whose colonization was significantly higher on the unsprayed okra crop with ESD PP borders than on both (sprayed and unsprayed) pure okra crops.
Fruits, 2012
Introduction. In the water-saving and income-generating agroforestry cropping systems developed a... more Introduction. In the water-saving and income-generating agroforestry cropping systems developed and promoted by the ICRISAT in the Sudano-Sahelian zone of West Africa, particularly in Niger, fruits of domesticated Ziziphus mauritiana ("apples of the Sahel") are severely damaged by fruit flies (Carpomya incompleta), and chemical pesticide application poses economic, environmental and human health problems. In the Bio-reclamation of Degraded Lands (BDL) system, apple of the Sahel is the main high-value crop, while in the Dryland Eco-Farm (DEF), it is grown alongside watermelon. Sclerocarya birrea (marula plum) is presently being investigated as a dryland tree species for fruit and oil production, either in orchards or such systems as BDL. Materials and methods. To complete preliminary results of earlier studies published elsewhere, we collected and incubated in 2010 ripe fruits of marula plum and watermelon in Sadoré, Niger, where the above-mentioned agroforestry systems are developed, and we recorded emerging fruit flies. We also conducted a spot-spraying experiment (using GF-120) in an apple of the Sahel orchard in Niamey in 2010; we recorded undamaged and damaged fruits and incubated the latter. In the same orchard, we set up in 2011 a fruit fly trapping survey targeting the invasive species Bactrocera invadens (Chempac ® traps using methyl eugenol as the attractant). Results and discussion. The results showed that only Ceratitis cosyra emerged from marula plums, and only Dacus spp. from watermelon. The GF-120 spot-spraying experiment showed that C. incompleta was not attracted / intoxicated, contrary to Ceratitis spp. and Dacus spp.; the sprayed trees yielded significantly more marketable fruits than unsprayed ones; only C. incompleta emerged from damaged fruit. Detection trapping revealed for the first time the presence of B. invadens in the Sahelian zone of Niger, including at the time of apple of the Sahel fruit production. Conclusion. This, alongside results of earlier studies, suggests a repellent effect of GF-120 on the monophagous C. incompleta species (Trypetinae), while it is attractive to oligophagous/polyphagous Dacinae fruit flies; some of them (e.g., Dacus spp.) damage watermelon, which is part of the DEF system, and produce fruit at the same time as the jujube tree. The prospects for harnessing these two opposite regulation pathways are discussed.
Agriculture, Ecosystems & Environment, 2014
From 2008 to 2010, the effect of a wind erosion-alleviating practice, that is, planting of windbr... more From 2008 to 2010, the effect of a wind erosion-alleviating practice, that is, planting of windbreaks of the perennial grass Andropogon gayanus Kunth on the populations of millet stem borer (MSB) Coniesta ignefusalis (Hampson) (Lepidoptera: Pyralidae) and the damage induced by this pest to pearl millet, was studied at Sadore (Niger). The extent of bored stems in the A. gayanus hedge bordering millet plots (23% on average) was significantly lower than in the millet plots (76% on average), with no MSB larva recovered, compared to an average of 2.2 larvae per stem in the millet plots over the three years. Andropogon grass was thus ruled out as a trap crop for MSB management. Under the conditions of this study, a pest regulation service by Andropogon grass hedges, synergistic with a potential wind erosion alleviating service, cannot be put forward.
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Papers by Alain Ratnadass