Charles Midega - Academia.edu (original) (raw)

Papers by Charles Midega

Intercropping is drawing increasing attention as a strategy to increase crop yields and manage pe... more Intercropping is drawing increasing attention as a strategy to increase crop yields and manage pest pressure; however the mechanisms of associational resistance remain controversial. We conducted a controlled experiment to assess the impact of co-planting with silverleaf Desmodium (Desmodium uncinatum) on maize secondary metabolism and resistance to herbivory by the spotted stemborer (Chilo partellus). Two maize varieties were grown either with Desmodium or adjacent to it in separate pots. Our findings indicate that co-planting with Desmodium influences secondary metabolism and herbivore resistance through both above and below-ground mechanisms. Stronger effects were generally observed when maize and Desmodium shared the same pot, implying that direct root contact or soil-borne cues play an important role in mediating associational effects on plant resistance in this system.

日本応用動物昆虫学会大会講演要旨, Mar 12, 2008

Urban agriculture & regional food systems, 2022

The majority of people in low‐ and middle‐income countries, such as Kenya, lack effective sanitat... more The majority of people in low‐ and middle‐income countries, such as Kenya, lack effective sanitation and waste management systems. Circular bionutrient economy (CBE) is emerging as a framework to safely reuse organic wastes in agriculture. This study aimed to characterize waste and sanitation systems in Kisumu City, Kenya, with a view to exploring opportunities for CBE in the Lake Victoria basin. Sanitation was characterized through a case study approach in a populous informal settlement, and waste was quantified in two markets in the city. The main toilet facility was pit latrine, although there were also some urine‐diverting dry toilets (UDDTs). One toilet served about 36 people. Over a 1‐mo period, the UDDTs yielded approximately 64,400 L of urine, whereas about 67,500 L of fecal sludge was emptied from the pit latrines, out of which only about 33,000 L (48.9%) was properly disposed of. About 3 t of waste was generated daily from the markets, 95% of which was organic, and was disposed of at an open dumpsite. Organic waste, including human excreta, contains large amounts of organic matter and plant nutrients, and can be processed for agricultural nutrient cycles. Additionally, black soldierly larvae can effectively convert organic waste into nutrient‐rich fertilizer and high protein biomass for animal feeds. These results suggest an opportunity for a CBE system in the region for sustainable organic waste management and urban sanitation, and with opportunity to improve livelihoods and equity.

Journal of Agronomy, Jun 15, 2018

bioRxiv (Cold Spring Harbor Laboratory), Feb 9, 2023

Introduction: Several Desmodium spp. are used as intercrops in push-pull pest management systems ... more Introduction: Several Desmodium spp. are used as intercrops in push-pull pest management systems to repel insect herbivores. In addition, Desmodium suppresses the parasitic weed Striga, and diversifies the soil microbiome with negative impacts on fungi. We investigated the impact of a 2-year cropping of five Desmodium species on soil microbiome populations. Methodology: Total DNA was obtained from root zone soil samples collected from a twoyears-old common garden experiment with replicated plots of five Desmodium spp. at the international centre for insect physiology and ecology (ICIPE), Mbita, Kenya. Subsequently, 16S and ITS DNA sequencing were performed and the data was analysed by using QIIME2 and Calypso. Results: Our findings show significant differences in composition and abundance of specific microbial taxa among the Desmodium plots and the bulk soil, with a stronger shift observed for fungal community profiles than bacteria. There was, however, no significant difference in overall diversity, richness and evenness of microbial communities among the Desmodium plots and the bulk soil. Similarly, beta diversity analysis did not reveal a significant association of variation to specific Desmodium spp. plots. Discussion and conclusion: This is the first study to compare impact and association of whole soil microbiomes to different Desmodium species. Whereas long-term Desmodium cropping clearly shifts whole microbiome communities, no significant difference in overall diversity and richness of microbial populations was observed among the studied plots. However, there was a divergence of individual taxa reflected on their increased abundance in association to specific Desmodium spp., pointing towards potential impact on ecosystem services. These findings indicate that significant shifts in whole microbial populations due to Desmodium spp. and thus potentially provision of associated ecosystem services require longer cultivation periods to solidify. Future studies should focus on techniques that monitor real-time changes in microbial populations such as RNA-seq to ascertain live and dead microbes, and thus infer ecological services.

PubMed, 2014

"Push-Pull" is an inexpensive and eminently practical strategy designed for developing countries ... more "Push-Pull" is an inexpensive and eminently practical strategy designed for developing countries in order to exploit sound principles of chemical ecology for agricultural pest management. This strategy is specifically suitable for small holder farmers. Their experience can easily be integrated into existing farming practices in their immediate environment. "Push-pull" within one and a half decades became widely established and meanwhile is greatly beneficial to practitioners in East Africa, mainly Kenya. The classical push-pull approach used for applied plant-insect management was pioneered by Khan and Pickett (2000) and subsequent papers of Pickett (2003) and Khan et al. (2006, 2008). Relevant plant species explored so far were maize or sorghum intercropped with other East African plants (Desmodium spp. resp. Melinis minutiflora) possessing natural chemicals repellent resp. attractive for stem borer moths Chilo partellus (Lepidoptera), whereby Desmodium spp. was grown inside the maize rows while M. minutiflora surrounded it. Both simultaneous actions combined resulted in a significant decrease of stem borers in the area to be protected. A benefit to cost ratio of 2.5 was realized. Within a period of 15 years the number of subscribing farmers substantially increased from a few dozen to more than 80,000 in 2014. Two experiments along the paths of chemical ecology were undertaken between Sept 2012 and Feb 2013: One was designed to investigate if the legume D. intortum known to produce repellent volatiles against stem borer moths induces defence in Zea mays varieties. We looked at two open-pollinated farmers' varieties and two commercial hybrid varieties suspecting the farmers' varieties to be responsive rather than the hybrids. However, no defence induction was detected in this study so far. This could be explained by an insufficient production of defence inducing volatiles in leaves of D. intortum whereas flowers might produce a sufficient response. More detailed study is needed. A second approach made use of species-specific insect monitoring traps baited with highly specific female sex pheromones for attracting and monitoring destructive insect pests. The female sex pheromone (8-methyl-decane-2-ol propanoate) of Diabrotica virgifera virgifera (Coleoptera: Chrysomelidae) (Western Corn Rootworm) is readily available as bait in the "Metcalf sticky cup trap" for trapping males, an extraordinarily sensitive technique for monitoring the presence or absence of male beetles in a given area. Li et al. (2006) had argued for the likelihood of easy immigration of this cosmopolitan maize pest into East Africa. Our results, however, so far indicate the absence of a local population in the area of Mbita, while not excluding its presence at Nairobi or Mombasa. Both investigations contribute to different aspects of Kenyan economic development and may be seen as two independent but complementary contributions towards livelihood improvement of small holder farmers in Kenya.

A presentation prepared by Zeyaur R. Khan and Charles A.O. Midega to the ASARECA/ILRI Workshop on... more A presentation prepared by Zeyaur R. Khan and Charles A.O. Midega to the ASARECA/ILRI Workshop on Mitigating the Impact of Napier Grass Smut and Stunt Diseases, Addis Ababa, June 2-3, 2010.

Genome Announcements, Apr 28, 2016

Phytoplasmas are bacterial plant pathogens with devastating impact on agricultural production wor... more Phytoplasmas are bacterial plant pathogens with devastating impact on agricultural production worldwide. In eastern Africa, Napier grass stunt disease causes serious economic losses in the smallholder dairy industry. This draft genome sequence of "Candidatus Phytoplasma oryzae" strain Mbita1 provides insight into its genomic organization and the molecular basis of pathogenicity.

Journal of Phytopathology, Jan 12, 2016

Production of Napier grass, Pennisetum purpureum, the most important forage crop in Africa, is se... more Production of Napier grass, Pennisetum purpureum, the most important forage crop in Africa, is severely constrained by Napier grass stunt (NGS) disease. Wild grasses have been identified as alternative hosts for NGS, but there is no record regarding the ability of this phytoplasma to infect cultivated food crops. To assess this threat, six crop species were placed around phytoplasma-infected Napier grass with the vector Maiestas banda (Hemiptera: Cicadellidae) in transmission cages for a period of 30 days. The crop plants were observed for 3 months after removal from the cages for disease development. Polymerase chain reaction based on the conserved 16S gene, primed by P1/P6-NapF/NapR nested primer sets, was used to diagnose phytoplasma in test plants, before and after transmission experiments. Pennisetum purpureum showed the highest infection level (81.3%), followed by Saccharum officinarum (56.3%), Eleusine coracana (50%), Sorghum bicolor (43.8%), Oryza sativa (31.3%) and Zea mays (18.8%). All the test plants remained symptomless except sugarcane that exhibited mild to moderate symptoms comprising yellow leaves and bright white or yellow midribs. Napier grass, however, was stunted with small yellow leaves. The study showed that food crops could be infected, suggesting their possible role as sources of inoculum for NGS and their contribution in the spread of the disease in regions where these crops are cultivated. This implies an additional disease cycle could occur for NGS disease, highlighting the challenges to development and implementation of management strategies for the disease.

Journal of Chemical Ecology, Nov 21, 2012

The boll weevil, Anthonomus grandis, has been monitored through deployment of traps baited with a... more The boll weevil, Anthonomus grandis, has been monitored through deployment of traps baited with aggregation pheromone components. However, field studies have shown that the number of insects caught in these traps is significantly reduced during cotton squaring, suggesting that volatiles produced by plants at this phenological stage may be involved in attraction. Here, we evaluated the chemical profile of volatile organic compounds (VOCs) emitted by undamaged or damaged cotton plants at different phenological stages, under different infestation conditions, and determined the attractiveness of these VOCs to adults of A. grandis. In addition, we investigated whether or not VOCs released by cotton plants enhanced the attractiveness of the aggregation pheromone emitted by male boll weevils. Behavioral responses of A. grandis to VOCs from conspecific-damaged, heterospecificdamaged (Spodoptera frugiperda and Euschistus heros) and undamaged cotton plants, at different phenological stages, were assessed in Y-tube olfactometers. The results showed that volatiles emitted from reproductive cotton plants damaged by conspecifics were attractive to adults boll weevils, whereas volatiles induced by heterospecific herbivores were not as attractive. Additionally, addition of boll weevil-induced volatiles from reproductive cotton plants to aggregation pheromone gave increased attraction, relative to the pheromone alone. The VOC profiles of undamaged and mechanically damaged cotton plants, in both phenological stages, were not different. Chemical analysis showed that cotton plants produced qualitatively similar volatile profiles regardless of damage type, but the quantities produced differed according to the plant's phenological stage and the herbivore species. Notably, vegetative cotton plants released higher amounts of VOCs compared to reproductive plants. At both stages, the highest rate of VOC release was observed in A. grandis-damaged plants. Results show that A. grandis uses conspecific herbivore-induced volatiles in host location, and that homoterpene compounds, such as (E)-4,8-dimethylnona-1,3,7-triene and (E,E)-4,8,12-trimethyltrideca-1,3,7,11-tetraene and the monoterpene (E)-ocimene, may be involved in preference for host plants at the reproductive stage.

Entomologia Experimentalis et Applicata

Farmers looking to maximize ecosystem services often use diversification practices on their field... more Farmers looking to maximize ecosystem services often use diversification practices on their fields to increase abundance and diversity of insect natural enemies. These practices affect functional traits of natural enemies such as body size that can play an important role in their effectiveness as biological control agents. However, landscape features out of the control of farmers might also affect functional traits of natural enemies and their herbivores, including land use surrounding farms. There have been few studies elucidating how landscape complexity and local diversity interact to affect functional traits, and ultimately ecosystem services such as predation on herbivore pests. We examined combined effects of landscape complexity and a local management practice (push‐pull) on lady beetle size, and its consequences for egg predation of lepidopteran pests in Kenyan smallholder maize farms. Cheilomenes sulphurea (Olivier) (Coleoptera: Coccinellidae), a potential predator of the i...

2016 International Congress of Entomology, 2016