Bioactivities of crude extracts of the candlewood Zanthoxylum xanthoxyloides Lam. (Rutaceae) against the cowpea beetle Callosobruchus maculatus (Walp)

The efficacy of petroleum-ether crude extracts of the candlewood, Zanthoxylum xanthoxyloides Lam. was assessed for their contact toxicity, feeding and oviposition deterrence to the cowpea beetle Callosobruchus maculatus (Walp). Percent mortality, number of progeny produced and damage caused to were dose– dependent. Root extracts was the most effective as toxicant to the beetles. The LD50 in 24 h topical application of root extracts was 4.98 μg. The LD50 (96 h toxicity in grain) suggests that root extract was highly toxic to C. maculatus. Development of eggs and larvae within grain kernels, as well as progeny emergence were significantly inhibited in treated grains. There were no progeny produced by C. maculatus in grains treated with dosage ³ 0.4 g per 100 g of grain. Root extracts provided the greatest protection of cowpea against feeding by C. maculatus with no observable feeding damage to grains treated with the highest dosages of the three materials. Extracts were repelled C. maculatus but with considerable variation in their repellent action. Z. xanthoxyloides contains phytochemicals, and crude extracts could be used as a botanical insecticide in alternative control strategies against C. maculatus. Keywords: Antifeedant, Bruchids, Botanical insecticides, Reproduction retardant, Toxicity. Int. J. Biol. Chem. Sci. Vol. 2 (3) 2008: pp. 316-32

Toxicity, growth regulatory and repellent activities of medicinal plant extracts on Musca domestica L. (Diptera: Muscidea)

Housefly, Musca domestica, is a major vector for many medical and veterinary pathogenic organisms. The development of naturally occurring insecticides, represent one of the most promising approachesfor their ecochemical control. Petroleum-ether extracts of Griffonia simplicifolia and Zanthoxylum xanthoxyloides were assessed for their toxicity, growth regulatory and repellency to the housefly. Percent mortality and index of repellency induced by the extracts against the insects were found to be dose-dependent. Seed extracts of G. simplicifolia and root extracts of Z. xanthoxyloides were the mosteffective as toxicants and repellents against the fly. The LD50 in 24 h topical application of seed extracts of G. simplicifolia and root extracts of Z. xanthoxyloides were 0.28 and 0.35 ìg, respectively. Seed extracts of G. simplicifolia evoked a very strong regulatory effect against the second larval instar of the housefly. The RD50 of crude extracts of G. simplicifolia and Z. xanthoxyloides against housefly ranged from 1.0 to 6.8 and 1.3 to 1.7 ìg cm–2, respectively. Extracts of the two plant species may be useful as insecticides for controlling the housefly and should be exploited as a component of integrated vector control strategies or could be useful in the search of new larvicidal naturalcompounds

Advances in crop insect modelling methods—Towards a whole system approach

A wide range of insects affect crop production and cause considerable yield losses. Difficulties reside on the development and adaptation of adequate strategies to predict insect pests for their timely management to ensure enhanced agricultural production. Several conceptual modelling frameworks have been proposed, and the choice of an approach depends largely on the objective of the model and the availability of data. This paper presents a summary of decades of advances in insect population dynamics, phenology models, distribution and risk mapping. Existing challenges on the modelling of insects are listed; followed by innovations in the field. New approaches include artificial neural networks, cellular automata (CA) coupled with fuzzy logic (FL), fractal, multi-fractal, percolation, synchronization and individual/agent based approaches. A concept for assessing climate change impacts and providing adaptation options for agricultural pest management independently of the United Nations Intergovernmental Panel on Climate Change (IPCC) emission scenarios is suggested. A framework for estimating losses and optimizing yields within crop production system is proposed and a summary on modelling the economic impact of pests control is presented. The assessment shows that the majority of known insect modelling approaches are not holistic; they only concentrate on a single component of the system, i.e. the pest, rather than the whole crop production system. We suggest system thinking as a possible approach for linking crop, pest, and environmental conditions to provide a more comprehensive assessment of agricultural crop production.Peer reviewe

The physiological responses of cacao to the environment and the implications for climate change resilience. A review

Cacao (Theobroma cacao L.) is a tropical perennial crop which is of great economic importance to the confectionary industry and to the economies of many countries of the humid tropics where it is grown. Some recent studies have suggested climate change could severely impact cacao production in West Africa. It is essential to incorporate our understanding of the physiology and genetic variation within cacao germplasm when discussing the implications of climate change on cacao productivity and developing strategies for climate resilience in cacao production. Here we review the current research on the physiological responses of cacao to various climate factors. Our main findings are 1) water limitation causes significant yield reduction in cacao but genotypic variation in sensitivity is evident, 2) in the field cacao experiences higher temperatures than is often reported in the literature, 3) the complexity of the cacao/ shade tree interaction can lead to contradictory results, 4) elevated CO2 may alleviate some negative effects of climate change 5) implementation of mitigation strategies can help reduce environmental stress, 6) significant gaps in the research need addressing to accelerate the development of climate resilience. Harnessing the significant genetic variation apparent within cacao germplasm is essential to develop modern varieties capable of high yields in non-optimal conditions. Mitigation strategies will also be essential but to use shading to best effect shade tree selection is crucial to avoid resource competition. Cacao is often described as being sensitive to climate change but genetic variation, adaptive responses, appropriate mitigation strategies and interactive climate effects should all be considered when predicting the future of cacao production. Incorporating these physiological responses to various environmental conditions and developing a deeper understanding of the processes underlying these responses will help to accelerate the development of a more resource use efficient tree ensuring sustainable production into the future

Sustainable management in crop monocultures: the impact of retaining forest on oil palm yield.

Tropical agriculture is expanding rapidly at the expense of forest, driving a global extinction crisis. How to create agricultural landscapes that minimise the clearance of forest and maximise sustainability is thus a key issue. One possibility is protecting natural forest within or adjacent to crop monocultures to harness important ecosystem services provided by biodiversity spill-over that may facilitate production. Yet this contrasts with the conflicting potential that the retention of forest exports dis-services, such as agricultural pests. We focus on oil palm and obtained yields from 499 plantation parcels spanning a total of ≈23,000 ha of oil palm plantation in Sabah, Malaysian Borneo. We investigate the relationship between the extent and proximity of both contiguous and fragmented dipterocarp forest cover and oil palm yield, controlling for variation in oil palm age and for environmental heterogeneity by incorporating proximity to non-native forestry plantations, other oil palm plantations, and large rivers, elevation and soil type in our models. The extent of forest cover and proximity to dipterocarp forest were not significant predictors of oil palm yield. Similarly, proximity to large rivers and other oil palm plantations, as well as soil type had no significant effect. Instead, lower elevation and closer proximity to forestry plantations had significant positive impacts on oil palm yield. These findings suggest that if dipterocarp forests are exporting ecosystem service benefits or ecosystem dis-services, that the net effect on yield is neutral. There is thus no evidence to support arguments that forest should be retained within or adjacent to oil palm monocultures for the provision of ecosystem services that benefit yield. We urge for more nuanced assessments of the impacts of forest and biodiversity on yields in crop monocultures to better understand their role in sustainable agriculture

Multi-stakeholder process strengthens agricultural innovations and sustainable livelihoods of farmers in southern Nigeria

Published online: 02 Nov 2017Purpose: In this paper, we explore the strategic role of Multi-stakeholder processes (MSP) in agricultural innovations and how it has impacted livelihood assets’ (LAs) capital dynamics of stakeholders in platforms in West Africa. Design/Methodology/Approach: We demonstrate how LA capitals and socio-economic dynamics induced by MSP can enhance cassava production efficiency but also create opportunities and challenges that influence platform dynamics and impacts. We use a multistage sampling procedure and sustainable livelihood model (e.g. stochastic frontier functions and Tobit regression) to analyse LA capital dynamics of the stakeholders. Findings: We showed that the LA of the MSP participants (0.72) was found to be significantly higher (χ2 = 3.732, p < .10) than that of the non-participants (0.45). The results further revealed a remarkable increase from 0 to 0.77 and from 0.33 to 0.82 for human capital and social capital, respectively, as stakeholders participate in MSPs’ activities. Practical implications: We recommend the institutionalization of MSP in the Agricultural Research for Development (AR4D) with more extension follow-up services so as to adequately and appropriately unleash the potentials in social capital networks that enable the development, effective dissemination and adoption of agricultural innovations. Theoretical implications: This study suggests that soft-transfer of technologies seems to dominate at MSP inception. But at maturity, the results of the struggle between researchers and farmers would lead to co-reaction and community-based research. Consequently, the knowledge and power dynamics that take place within the MSP should be considered the centre of co-construction and platform dynamics. Originality/Values: The study provided a practical experience on how MSP can be institutionalized in the AR4D programmes to support agricultural innovation systems and foster pro-poor growth and livelihoods

Entomopathogenic Fungi as Endophytes for Biological Control of Subterranean Termite Pests Attacking Cocoa Seedlings

This study was conducted in the scope of developing a sustainable effective approach against subterranean termite pests using entomopathogenic and endophytic fungus-based biopesticides. Termites, Odontotermes spp. workers, were tested for their susceptibility to 15 entomopathogenic fungal isolates through the direct spraying of conidia suspensions at 1 &times; 108 conidia/mL. In general, all the isolates screened were pathogenic, with 100% mortality 4&ndash;7 days post-inoculation. However, the most virulent isolates were Metarhizium brunneum Cb15-III; the M. anisopliae isolates ICIPE 30 and ICIPE 60; Hypocrea lixii F3ST1; and the Beauveria bassiana isolates ICIPE 279, ICIPE 706 and ICIPE 662. These isolates were further tested for their endophytic colonization of cocoa seedlings using seed soaking, soil drench and foliar spray at 1 &times; 108 conidia/mL. The colonization of the plant tissues by the fungi was determined using a culture-based technique. Only the B. bassiana isolates ICIPE 706 and ICIPE 279, and H. lixii F3ST1 colonized the cocoa seedlings, with varied colonization rates among isolates and inoculation methods. Three naturally occurring endophytes&mdash;Trichoderma asperellum, Fusarium solani and F. redolens&mdash;were also isolated from the cocoa seedling tissues. These findings suggest that cocoa seedlings are conducive to endophytic fungal growth either occurring naturally or from artificial inoculation Our findings could possibly lead to an innovative approach to the management of herbivory and subterranean termite pests in cocoa agroforests

Testing a co-formulation of CO2-releasing material with an entomopathogenic fungus for the management of subterranean termite pests

Ambele CF, Bisseleua HDB, Akutse KS, et al. Testing a co-formulation of CO2-releasing material with an entomopathogenic fungus for the management of subterranean termite pests. MYCOLOGICAL PROGRESS. 2019;18(9):1201-1211.Termites cause significant damage to cocoa trees. Entomopathogenic fungi (EPFs) such as Metarhizium brunneum have been considered as a sustainable alternative to abusive use of insecticides against termites. However, potent EPF application is limited by its repellency effects, host avoidance, and termite defense mechanisms such as grooming among nest mates. Termites use CO2 to locate plant roots. This study investigated whether CO2-emitting capsules could attract termites. Capsules formulated without fungus (CEC) as well as those formulated with M. brunneum Cb15-III (CECEPF) were tested for attractiveness to termites with other attractive components using modified four-arm olfactometers. Worker termites' infection by the fungus growing from the capsules as well as its horizontal transmission was assessed through the autodissemination approach. Significantly, more termites were attracted to CEC compared with other attractive components. Higher number of termites was attracted by CECEPF and cocoa seedlings than dry wood and yeast in a choice test. When termites were directly exposed to sporulating capsules, 100% mortality was obtained within 5 days. However, in the horizontal transmission experiment, no significant differences were observed as regards termites' mortality in the treatment compared with the control groups. CECEPF did not cause any apparent repellency to termites as compared with CEC. This strategy offers high potential to promote biological termite control using CECEPF as alternative to insecticides. Further studies are warranted to evaluate the efficacy of these capsules under field conditions and explore their commercialization for termite management