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‘One health’ (OH) is a cross-sectoral approach that addresses human, plant, animal, and environmental health problems. The initiative stems from recognition of the convoluted linkages among global health risks and the need for coherent multipronged countermeasures. For agriculture, environmental degradation and biodiversity depletion wrought by heavy reliance on inorganic inputs to meet the needs of the ever-growing human population, are a matter of societal concern. Agroecological-based farming strategies have therefore aptly been promoted as an alternative. The push-pull technology (PPT), which was originally developed to combat stemborer pests and later the parasitic weed Striga is one such example. Undoubtedly, the PPT`s ability to maintain soil health and fertility, human and animal nutrition, and food safety together with crop protection against pests remains a progressive approach for buttressing food production among resource-constrained farmers in sub-Saharan Africa (SSA). In a bid to elevate its nutrition-sensitivity status, we recently intensified the cereal PPT by adding vegetables and legumes whilst simultaneously closing yield gaps through judicious usage of land, and environmental and crop protection based on farmer needs. Such context-based interventions, unlock new benefits for farmers and open new frontiers for research in pest and biodiversity management emanating from crop production infused with food safety and environmental stewardship. Whilst OH has largely received attention regarding animal health and zoonotics, we here opine how sustainably managed crop health, in the vegetable intensified PPT, contributes to the same outcomes through human and animal nutrition, food safety that bolsters developmental goals in gender equity and food security. We conclude that the cropping system can even contribute to fight against zoonotic diseases if companion plants that fend off diseases vectors are incorporated.

This study aimed to evaluate the performance of broiler chickens fed on 3 black soldier fly larvae (BSFL) (Hermetia illucens) and Greenleaf desmodium (Desmodium intortum)-based meals. We evaluated growth performance, carcass quality, and profitability under various commercial pathways (doorstep, retail, whole, and assorted). Desmodium and BSFL powders were formulated into 3 ratios: T1 25:75, T2 50:50, and T3 75:25. A commercial feed was used as a control. One hundred and twenty mixed-sex 1-day-old broiler chicks (Cobb) were reared in pens for 42 d in a completely randomized design. The chickens were weighed weekly to monitor their growth rate. After the 42-day rearing period, they were slaughtered for carcass quality evaluation and recording of the weights of internal organs. During the initial growth phase (7–21 d), significant effects of fish meal replacement were found on the chickens' average weight (P

Background The fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith) is a serious pest of maize. Farming systems such as push-pull or maize-legume intercropping have been reported to reduce FAW infestations significantly. However, the exact mechanisms involved in FAW management have not been practically elucidated. We therefore assessed larval host preference, feeding and survival rate when exposed to four host plants commonly used in push-pull and legume intercropping. We also compared adult moths' oviposition preference between maize and other grasses used as trap crops in push-pull. Results The larval orientation and settlement study showed that maize was the most preferred host plant followed by bean, desmodium and Brachiaria brizantha cv Mulato II. The larval arrest and dispersal experiment showed that mean number of larvae was significantly higher on maize than on Desmodium or B. brizantha cv Mulato II. However, no significant differences were found between maize and bean after 24 h. Maize was the most consumed plant, followed by bean, desmodium and finally brachiaria. The mean percentage of survival to the pupation stage was significantly higher on maize. The study on FAW oviposition preference showed no significant differences in egg deposited between maize and other grasses. However, B. brizantha cv Xaraes, which received more eggs than maize, could be a promising alternative to B. brizantha cv Mulato II for the control of FAW. Conclusion The study provides a better understanding of the mechanisms involved in the control of fall armyworm under the push-pull and maize legume intercropping. © 2021 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

The fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith), which has recently invaded the African continent, has become a new threat to cereal production. Being an invasive pest with certain competitive advantages, the impact of FAW on other lepidopteran pests is unclear. This study assessed the infestation of FAW and cereal stemborers on maize and sorghum under mono-cropped systems that are adjacently placed in five districts in Uganda. Data on maize and sorghum infestation cereal stemborers and FAW was collected at 6, 9 and 16 weeks after planting (WAP), to determine intensity and severity. Cereal stemborer infestations on maize at 6, 9 and 16 WAP were only 36.7%, 48.2% and 24.0%, respectively, which was significantly lower than the infestations on sorghum, at 55.5%, 53.2%, 64.0%, respectively. On the contrary, the infestations of FAW on maize at 6, 9 and 16 WAP were 89.5%, 84.7% and 86.0%, respectively, while on sorghum they were 51.0%, 56.5% and 47.0, respectively. The severity of stemborers on sorghum was statistically higher than on maize, whereas the damage severity of FAW was generally higher on maize than on sorghum. Intensity of damage and cavity length due to stemborer on sorghum was higher than on maize. Historical records showed that in maize stemborer infestation could reach 60%. This infestation started significantly declining in 2016, suggesting an early arrival of FAW in Uganda. The present study indicates a possible displacement of stemborer from maize onto sorghum. Any Integrated Pest Management (IPM) package should consider managing FAW and stemborer together in both maize and other cereal hosts.

Maize grown under push-pull cropping system has been reported to contain lower concentrations of fumonisin and aflatoxin than maize monocrop. This study determined the inhibitory effect of desmodium root extracts on spore germination and radial growth of toxigenic Aspergillus flavus and Fusarium verticillioides. Aspergillus flavus and F. verticillioides were isolated from maize and soil and tested for ability to produce aflatoxin and fumonisin by inoculation on mycotoxin-free maize. Aflatoxin and fuminisin were detected and quantified by direct competitive ELISA. Desmodium roots were dried, ground to fine powder and extracted with methanol and dichloromethane and evaluated for anti-fungal activity by inhibition of spores of A. flavus and F. verticillioides potato dextrose agar (PDA) medium. Isolates of F. verticillioides produced up to 599,741 µg/kg fumonisin while isolates of A. flavus produced up to 199,184 µg/kg aflatoxin. Desmodium root extracts reduced germination of A. flavus spores and F. verticillioides by 9.6% and 43.8%, respectively and reduced their respective colony radial growth by 15% and 57%. The results suggested that desmodium roots contain chemical compounds that inhibit growth of A. flavus and F. verticillioides. This may explain the reduction in infection of maize with mycotoxin-producing fungi before harvest in push-pull cropping systems by reducing the pathogen inoculum in the soils. Determination of the active compounds in the root exudates is recommended

SummaryProduction of cereal crops in sub-Saharan Africa is threatened by parasitic striga weeds and attack by stemborers and the invasive fall armyworm (FAW), compounded by increasing hot and dry conditions. A climate-smart push-pull technology (PPT) significantly reduces effects of these biotic challenges. To improve further resilience of the system to climate change, more adapted and suitable companion plants were identified and integrated in a new version of PPT, termed ‘third generation PPT’. Our study evaluates field performance and farmer opinions of this new version in comparison with the earlier version, climate-smart PPT, and farmers’ own practices of growing maize in controlling stemborers, FAW, and striga weeds. Trials were conducted across five locations in western Kenya for two cropping seasons in the year 2019 following a one-farm one-replicate completely randomized design. We assessed infestation on striga, stemborers, and FAW, and yield performance of the three cropping systems. We also sought the opinions of the hosting farmers through semi-structured questionnaires that were administered through individual interviews. Both PPT plots recorded significantly (P < 0.05) lower striga count, FAW, and stemborer damage, and higher grain yield than in plots that followed farmers’ own practices. There was no statistically significant difference between the two PPT plots except for stemborer damage for which the third generation PPT recorded higher damage than the climate-smart PPT. However, farmers preferred the third generation PPT for important traits possessed by its companion plants which their counterparts in climate-smart PPT are deficient. The cultivar Xaraes was rated as ‘very good’ for resistance to spider mites, biomass yield, and drought tolerance while Desmodium incanum was rated ‘very good’ for seed production and drought tolerance. The third generation PPT is based on companion crops that are more resilient to hot and dry conditions which are increasing rapidly in prevalence with climate change. This version therefore presents a better option to upscale the technology and meet different needs of farmers especially in arid and semi-arid conditions.

Adoption studies have identified gender as one of the factors that determine technology uptake and this has been linked to women’s access to farming information or lack of it. Technology scaling up systems should utilise pathways that are compatible with the needs of rural women, who have to juggle farming with other household chores. Unfortunately, there has been limited effort to evaluate the suitability of the information pathways used to specific gender. The current study evaluates the appropriateness of field days with respect to gender of the participants. Data were collected from selected farmers who attended field days in Kenya, Uganda and Tanzania in 2014. A total of 2 615 participants were interviewed out of 6 221 who attended field days. Descriptive analysis and ordered probit and logit models were used for analysis. The majority of the participants in Kenya and Tanzania were women (51.3% and 62.6%, respectively), whereas in Uganda the majority of participants were men (57.4%). Most participants were middle aged (42 years for women and 45 years for men). The majority of the women (54.1%) had primary level education, with only 29.1% having secondary education, whereas 41% and 40.1% of men had attained primary and secondary education, respectively. The results from the econometric models shows that gender, age, education, being push-pull farmers, perceptions on Striga severity were the main significant determinants of knowledge for the ordered probit. Conversely, gender of the participant, perception on stemborers and Striga weed severity and having mobile phones were the significant determinants of willingness to adopt. The two models were significant at 1% (p

Consumption of maize contaminated with mycotoxins has been associated with detrimental health effects. A farm survey covering 116 push‐pull and 139 non‐push‐pull cropping systems was conducted to determine the socio‐economic and agronomic factors that influence farmers’ knowledge on incidence and contamination of maize by ear rots and associated mycotoxins in western Kenya. All the respondents were smallholder farmers between the ages of 23 and 80 years, with 50% of them being female. Maize samples were collected from the standing crop in the field of each interviewed farmer and analyzed for aflatoxin and fumonisin. Only a small proportion of farmers had knowledge of aflatoxin and ear rots in maize. Overall, less than 20% of maize samples were contaminated with both aflatoxin and fumonisin, and more maize samples were contaminated with fumonisin as compared to aflatoxin. Proportions of maize samples containing higher than the acceptable Kenyan regulatory threshold (10 µg/kg) for aflatoxin and European Commission regulatory threshold (1,000) µg/kg for fumonisin were lower in maize samples from push‐pull cropping system. Age of farmer and county of residence were significantly and positively associated with knowledge of aflatoxin, while cropping system, county of residence, and level of education were positively associated with knowledge of maize ear rots. There was strong correlation between knowledge of maize ear rots and knowledge of aflatoxin. Levels of both aflatoxin and fumonisin were significantly and positively associated with the use of diammonium phosphate (DAP) fertilizer at planting. Aflatoxin levels were also positively associated with stemborer damage. Agronomic practices were not significantly different between push‐pull and non‐push‐pull farmers. However, use of DAP fertilizer was the most important agronomic factor since it was associated with both aflatoxin and fumonisin contamination of maize. These results imply that creating awareness is key to mitigation of ear rots and mycotoxin contamination of maize. The results also suggest that the levels of aflatoxin and fumonisin in maize in western Kenya were influenced both by pre‐harvest agronomic practices and by the cropping system adopted, push‐pull or not.

Weeds are one of the major restrictions to sustaining crop productivity. Weeds often outcompete crops for nutrients, soil moisture, solar radiation, space and provide platforms for breeding of pests and diseases. The ever-growing global food insecurity triggers the need for spatially explicit innovative geospatial technologies that can deliver timely detection of weeds within agro-ecological systems. This will help pinpoint maize fields to be prioritized for weed control. Satellite remote sensing offers incomparable opportunities for precision agriculture, ecological applications and vegetation characterisation, with vast socioeconomic benefits. This work compares and evaluates the strength of Sentinel-2 (S2) satellite with the constellation of Dove nanosatellites i.e. PlanetScope (PS) data in detecting and mapping Striga (Striga hermonthica) weed within intercropped maize fields in Rongo sub-county in western Kenya. We applied the S2 and PS derived spectral data and vegetation indices in mapping the Striga occurrence. Data analysis was implemented, using the Guided Regularised Random Forest (GRRF) classifier. Comparatively, Sentinel-2 demonstrated slightly lower Striga detection capacity than PlanetScope, with an overall accuracy of 88% and 92%, respectively. The results further showed that the VNIR (Blue, Green Red and NIR) and the Atmospheric resistance Vegetation Index (ARVI) were the most fundamental variables in detecting and mapping Striga presence in maize fields. Findings from this work demonstrate that Sentinel-2 data has the capability to provide spatial explicit near real-time field level Striga detection – a previously daunting task with broadband multispectral sensors.

Production of maize, Zea mays L. (Poaceae), in sub-Saharan Africa is threatened by a new invasive pest, fall armyworm (FAW), Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae). To mitigate this threat, push-pull companion cropping, a system originally developed for management of lepidopteran stemborers, may be used to control FAW. The original system involved trap crops that functioned as a 'pull' component to attract moths away from the main crop. How grass species can be used as trap crops in a push-pull system to control FAW is a question that remains to be answered, because maize is already a highly preferred host plant. Therefore, we tested oviposition preference of FAW female moths in no-choice and two-choice experiments and larval performance on six selected grasses (Poaceae) to assess their roles as trap crop 'pull' plants in the system. In no-choice tests, numbers of eggs deposited on Brachiaria brizantha (Hochst. ex A. Rich.) R. Webster cv. 'Piata', cv. 'Mulato II', and cv. 'Xaraes', and Napier grass (Pennisetum purpureum K. Schumach) cv. 'South Africa' were not statistically different from those deposited on maize. In two-choice tests between grasses and maize, there were no significant differences in number of eggs laid when the plants were of the same size. However, in two-choice tests with maize plants half of the size of the grasses, significantly more eggs were laid on B. brizantha cv. Xaraes and P. purpureum cv. South Africa than on maize, suggesting that crop phenology could make a difference. Numbers of larvae arrested on grass leaf cuts were considerably lower than those on maize leaf cuts after 48 h. In two-choice tests with maize, molasses grass (Melinis minutiflora P. Beauv.) was the only grass that was significantly preferred to maize for larval settlement after 24 h. After 48 h in the two-choice test, it was the only grass that retained larvae, although the larval count was significantly lower than on maize. Our data show that none of the grasses tested were strongly preferred to maize, but the results indicate plants attractive to FAW adults and larvae that could be utilized in a multiple trap crop approach to target various stages of the pest. Furthermore, results indicate the importance of planting these companion plants earlier than maize.

The fall armyworm (FAW) has recently invaded and become an important pest of maize in Africa causing yield losses reaching up to a third of maize annual production. The present study evaluated different aspects of resistance of six maize cultivars, cropped by farmers in Kenya, to FAW larvae feeding under laboratory and field conditions. We assessed the arrestment and feeding of FAW neonate larvae in no-choice and choice experiments, development of larvae-pupae, food assimilation under laboratory conditions and plant damage in a field experiment. We did not find complete resistance to FAW feeding in the evaluated maize cultivars, but we detected differences in acceptance and preference when FAW larvae were given a choice between certain cultivars. Moreover, the smallest pupal weight and the lowest growth index were found on ’SC Duma 43′ leaves, which suggests an effect of antibiosis of this maize hybrid against FAW larvae. In contrast, the highest growth index was recorded on ‘Rachar’ and the greatest pupal weight was found on ‘Nyamula’ and ‘Rachar’. The density of trichomes on the leaves of these maize cultivars seems not to be directly related to the preference of neonates for feeding. Plant damage scores were not statistically different between cultivars in the field neither under natural nor artificial infestation. However, plant damage scores in ‘Nyamula’ and ‘Jowi’ tended to be lower in the two last samplings of the season compared to the two initial samplings under artificial infestation. Our study provides insight into FAW larval preferences and performance on some African maize cultivars, showing that there are differences between cultivars in these variables, but high levels of resistance to larvae feeding were not found.

Mycotoxins are harmful to health and mainly arise from ear rots, affecting maize in the field. This work analysed the effect of the cropping system on ear rot and final effect on mycotoxins from four sub-counties (districts) of western Kenya, Butere, Kisumu, Siaya and Vihiga, where plots comprising maize planted either as pure stand or in mixture with legumes, predominantly common bean treated as “Maize Monocrop” (MM), were used as control for those of climate-smart push-pull strategy treated as “Push-Pull” (PP). Symptomatic and asymptomatic maize ear samples were analysed for total aflatoxin (AF), total fumonisins (FB), deoxynivalenol (DON) and zearalenone (ZEA) using Enzyme-Linked Immunosorbent assay (ELISA). Cropping system had very high significant effect on ear rot incidence and severity. In general, low incidence was observed in PP (7.3 %) than MM (20.8 %). Similar trend was also observed on ear rot severity in PP and MM as follows: diplodia (1.15 and 1.85), gibberella (0.62 and 0.84), aspergillus (0.09 and 0.25), fusarium (0.19 and 0.68) and penicilium (0.03 and 0.05). A high proportion of ZEA (100%), AF (93.3%), DON (80.0%) and FB (65.9%) were observed in symptomatic samples than in ZEA (90.3%), DON (51.6%), FB (38.7%) and AF (3.2%) in asymptomatic samples. Low ear rot incidence and severity was more in PP than MM, and proportion of mycotoxins on asymptomatic ears; suggesting the potential of cropping system in managing ear rots and ultimately limiting mycotoxins. Thus the study highlighted the need to adopt cropping systems to deal with mycotoxins, and also recommends surveillance and awareness on emerging mycotoxins: ZEA and DON. Key words: Push-pull, maize monocrop, aflatoxins, fumonisins, deoxynivalenol, zearalenone.

Fall armyworm (FAW) Spodoptera frugiperda invaded Africa, with the first detections being reported in Central and Western Africa in early 2016, and now affects at least 40 countries in Africa, causing up to total crop loss amounting to over $6.2 billion p.a. FAW is an invasive polyphagous pest that causes damage to economically important crops and has recently been reported in the Indian sub-continent. Effective control of FAW through use of synthetic chemical pesticides and genetically modified crops such as Bt maize faces challenges including improper use, unaffordability by smallholder farmers and development of resistance by the pest. Additionally, dispersal of FAW larvae into the lower maize plant canopy keeps them out of reach of topical insecticide applications. Integrated pest management (IPM) packages like the push-pull technology which eliminate pesticide use, and deploy natural processes are more suitable and cost-effective. Push-pull is a farming system intensification approach that involves attracting insect pests with trap plants (pull) such as Napier grass (Pennisetum purpureum) or Brachiaria grass, while driving them away from the main crop using a repellent intercrop (push), Desmodium spp., commonly known as desmodium, and attracting natural parasitoids and predators to the field. In the rhizosphere, chemicals secreted by desmodium roots inhibit attachment of germinated striga to maize or sorghum roots and abort germination of striga seeds which are rapidly depleted in the soil. Moreover, it improves soil fertility by fixing nitrogen, improving carbon sequestration, organic matter, moisture retention, and soil biota, and prevents further degradation of soil. The climate-adapted push-pull technology significantly reduces plant damage by FAW and is the first IPM management tool for the pest in Africa, and is well suited to agro-ecosystem intensification needs of smallholder mixed farming systems in Africa and beyond. Both the African and the Asian continents provide favourable climatic conditions for sustained reproduction of the FAW, which is expected to result in severe damage to crops; and being a new pest in both continents, it might have few natural enemies. Conventional control methods have limited effectiveness, as explained above. Therefore, an IPM approach that is compatible with mixed cropping farming systems of small and medium scale farmers is necessary. The climate adapted push-pull is the first demonstrated IPM management tool for the FAW in Africa. The technology combines this with other concomitant benefits including control of stemborers and the parasitic striga weeds, improvement of soil health through factors such as nitrogen fixation by desmodium, natural mulching, moisture retention and improvement of soil organic matter and soil biota. The combined benefits, including control of FAW, result in ecologically sustainable higher crop yields, and well suited to agro-ecosystem intensification needs of smallholder mixed farming systems in Africa and beyond.

Push–pull technology (PPT) simultaneously reduces the impact of three major production constraints, pests, weeds and poor soil, to cereal–livestock farming in Africa. In order to ascertain the social value of the technology and to make decisions about the trade-offs in the allocation of scarce resources in research, gross margin analysis and the Dynamic Research for Evaluation Management economic surplus model were applied to calculate and analyze the benefits of PPT for 568 households located in four districts in eastern Uganda. The results showed that with PPT the economy of these districts would derive an overall net gain of 3.8 million USD. At a discount rate of 12% for a period of 20 years (2015–2035), Net Present Value was about 1.6 million USD, the internal rate of return 51%, and the Benefit to Cost Ratio 1.54. This implies that PPT is economically viable and profitable. Hence the technology should be further up-scaled and disseminated to other regions to reduce poverty and increase household food security.

Fall armyworm, Spodoptera frugiperda (J E Smith), an economically important pest native to tropical and subtropical\ud America has recently invaded Africa, causing substantial damage to maize and other crops. We evaluated\ud functionality of a companion cropping system, ‘climate-adapted push-pull’, developed for control of cereal\ud stemborers in drier agro-ecologies, as an added tool for the management of fall armyworm. The technology\ud comprises intercropping maize with drought-tolerant greenleaf desmodium, Desmodium intortum (Mill.) Urb.,\ud and planting Brachiaria cv Mulato II as a border crop around this intercrop. Protection to maize is provided by\ud semiochemicals that are emitted by the intercrop that repel (push) stemborer moths while those released by the\ud border crop attract (pull) them. 250 farmers who had adopted the technology in drier areas of Kenya, Uganda\ud and Tanzania were randomly selected for the study during the long rainy season (March-August) of 2017. Each\ud farmer had a set of two plots, a climate-adapted push–pull and a maize monocrop. Data were collected in each\ud plot on the number of fall armyworm larvae on maize, percentage of maize plants damaged by the larvae and\ud maize grain yields. Similarly, farmers' perceptions of the impact of the technology on the pest were assessed\ud using a semi-structured questionnaire. Reductions of 82.7% in average number of larvae per plant and 86.7% in\ud plant damage per plot were observed in climate-adapted push-pull compared to maize monocrop plots.\ud Similarly, maize grain yields were significantly higher, 2.7 times, in the climate-adapted push-pull plots. Farmers\ud rated the technology significantly superior in reducing fall armyworm infestation and plant damage rates. These\ud results demonstrate that the technology is effective in controlling fall armyworm with concomitant maize grain\ud yield increases, and represent the first documentation of a technology that can be immediately deployed for\ud management of the pest in East Africa and beyond.

Soil degradation is a major underlying cause of poverty and malnutrition in smallholder agrarian communities across the globe. Legume diversification, through polyculture or intercropping, is a strategy that increases yields and income while improving family nutrition. However, the potential for these legume-cereal intercrops to restore soil functions in smallholder fields remains uncertain, with many studies failing to detect increases in soil organic matter (SOM). In sub-Saharan Africa, smallholders typically grow maize either intercropped with short-lived annual food legumes or as a monoculture. Recently, a novel maize system which includes perennial legumes in the genus Desmodium as intercrops, known as “push-pull” (hereafter, PP) has been increasingly adopted by smallholders across the region. The yield, nutritional and economic benefits of the PP system are well-documented. We investigated the effects of PP maize intercropping on soil fertility compared to the predominant maize culture systems (hereafter, NPP) using soils from long-term experiments and smallholder fields in western Kenya. Maize-desmodium intercrops promoted SOM accrual and increased plant available phosphorus. In the long-term research station experiments soil organic N was 20% greater and labile organic N reserves were five-fold greater in PP compared to NPP soils. Despite equal P fertilizer application rates, extractable soil P was two-fold greater in PP compared to NPP soils. Soils under maize-food legume intercrops did not show any detectable accrual of SOM compared to maize monocultures. Soil benefits in smallholder PP fields tended to mirror those found in the controlled experiments. Taken together, our results demonstrate that the perennial legumes in PP system restore soil function and fertility. Developing additional well-designed intercropping systems that include perennial legumes could play a significant role in reversing the trajectory of soil degradation in smallholder farming systems while enhancing human well-being.

This study examined the impact of push-pull technology (PPT) on the nutritional status of children aged 1-12 years. Non-push-pull (NPPT) farmers were used as a control group to establish a comparative model for this study. It determined household production, consumption, and surpluses, comparing the PPT adopters to the nonadopters; found out the incomes and food expenditures from farm products; found out the household dietary diversity scores; and finally found the nutritional status of the two household groups. A six faceted household-level metrics was employed. A sample of 216 households that registered 326 children was derived. This study was conducted in western Kenya: Busia, Butere, Siaya, Vihiga, Kisumu, and Migori. In this study 53% were male and 47% female from the households assessed. Households with married couples were 87.5%, 1.9% were single parents, 0.5% were separated and 10.2% were widowed. Averagely, 7.20 members came from PPT households, while 6.99 were from NPPT households. Each household (both PPT and NPPT) had an average number of three children. The study further showed that 88 households of PPT had their income sources from farm products sales as NPPT had 67 households on the same. Income was averagely 126.29US$ for PPT and 91US$ for NPPT. Push-pull households had 1303 Kgs of farm production while NPPT had 578 Kgs per year. The scale of agriculture to nutrition benefits recorded 8.7/10 for PPT and 7.14/10 for NPPT. Finally, PPT registered 12% of ≥+2SD, 84% of between -2 and > +2SD and 4% of ≤ -2SD for children under five years and 3% of ≥+2SD, 89% of between -2 and > +2SD and 8% of ≤ -2SD for children aged between 6 to 12 years. Non Push-pull households controversially registered 3% of ≥+2SD, 61% of between -2 and > +2SD and 36% of ≤ -2SD for children less than five years and 3% of ≥+2SD, 53% of between -2 and > +2SD and 44% of ≤ 2SD for children aged between 6 to 12 years. In conclusion, PPT is proven as an agricultural intervention that has enhanced nutritional improvement. Keywords: Push-pull Technology (PPT), Non Push-pull Technology (NPPT), nutrition, dietary diversity, food security, Body Mass Index (BMI), agriculture

The paper evaluates the impact of adoption of push-pull technology (PPT) on household welfare in terms of productivity, incomes and poverty status measured through per-capita food consumption in eastern Uganda. Push-pull is a habitat management strategy for the integrated management of stemborers, striga weeds and poor soil fertility involving the use of a natural repellent (push) and an attractant (pull). This biological technology simultaneously reduces the impact of three major production constraints to cereal-livestock farming in Africa − pests, weeds and poor soil. Cross sectional survey data were collected from 560 households in four districts in the region (Busia, Tororo, Bugiri and Pallisa), in November and December 2014. Generalized propensity scoring (GPS) was used to determine the intensity of adoption of the technology (i.e., land area allocated to PPT) and also to estimate the dose-response function (DRF) relating intensity of adoption and household welfare. Results revealed that with increased intensity of reported adoption of PPT, the probability of being poor declined through increased maize yield per unit area, incomes, and per capita food consumption. However, its impact varied with the intensity of adoption. With an increase in the area allocated to PPT from 0.025 to 1 acre, average maize yield per unit area increased from 27 kg to 1400 kg, average household income increased from 135 US$ (Uganda Shilling (USh) 370,000) to 273 US$ (USh 750,000) and per capita food consumption increased from 15 US$ (USh 40,000) to 27 US$ (USh 75,000). The average probability of a household being poor (below a rural poverty line of US$ 12.71) declined from 48% to 28%. These findings imply that increased investment in the dissemination and expansion of PPT is essential for poverty reduction among smallholder farmers in Uganda.

It is imperative to establish the distribution and density of soil fungal communities as a requisite for formulating strategies for management of ear rot infections and mycotoxin contamination. In a two seasons study, short (SR) and long rainy (LR) seasons, we investigated the distribution of Aspergillus and Fusarium fungi causing ear rots and producing mycotoxins from 120 soil samples collected from maize fields under push-pull (PP) and maize monocrop (MM) systems in Western Kenya. Cultural methods were used for identification of Aspergillus and Fusarium species, while molecular techniques were used for confirmation of Fusarium section Liseola. Detection of total aflatoxins in cultures of section Flavi isolates was carried out by enzyme-linked immunosorbent assay (ELISA). A total of 338 fungi were isolated; 80% were identified as Aspergillus and 4.4% Fusarium. The distribution of fungi was significant with season but not cropping systems. The frequency of occurrence was higher during the LR (68.4%) than the SR (31.6%). In cropping systems, the frequency of occurrence of Aspergillus flavus was higher in MM (60.2%) than PP (39.8%). However, Aspergillus parasiticus was more frequent in PP (71.4%) than MM (28.6%); and during the SR (78.6%) than the LR (21.4%). Majority (81.3%) of A. flavus and A. parasiticus were toxigenic. There was low recovery of Fusarium species in soil samples. These findings show that soils from both cropping systems are potential for Aspergillus infection and aflatoxins contamination; however, low Fusarium distribution in soil suggest external inoculum source for Fusarium ear rot infections common in most maize fields in Western Kenya. Key words: Aspergillus, Fusarium section Liseola, push-pull, soil.

Napier grass stunt (NGS) disease is a major threat to Napier grass cultivation and the smallholder dairy industry in East and Central Africa. The disease is caused by a phytoplasma, which is transmitted by the leafhopper Maiestas banda (Kramer) (Hemiptera: Cicadellidae). The current study was conducted to identify among 65 Napier grass accessions that could be resistant to NGS disease using the loop-mediated isothermal amplification of DNA (LAMP). The accessions were caged with NGS phytoplasma-infected Napier grass as inoculum source and M. banda as the vector. All Napier grass accessions were subjected to phytoplasma testing thereafter 18 phytoplasma negative and five asymptomatic accessions were selected and used in further screening by subjecting the extracted DNA to LAMP. Plant response to the NGS phytoplasma by symptom expression, impact on yield-related parameters and phytoplasma infection was used to evaluate tolerance or resistance over a period of three months. Most Napier grass accessions were susceptible to the disease except plants belonging to accession 16789 which were negative by LAMP. Napier grass accession 16807 was found to be tolerant with 60% plants positive by LAMP and 90% plants symptomless. Accessions 16822 and 16817 had moderate tolerance with one and two plants positive by LAMP, respectively. Accession 16812 was slightly tolerant with 58.3% plants positive by LAMP and 33.3% of the plants showing symptom remission in the second re-growth. This study indicates there could be resistance and tolerance to NGS disease which could be exploited in the development of an integrated management strategy for this disease.

The entire process of agricultural and horticultural food production is unsustainable as practiced by current highly intensive industrial systems. Energy consumption is particularly intensive for cultivation, and for fertilizer production and its incorporation into soil. Provision of nitrogen contributes a major source of the greenhouse gas, N2O. All losses due to pests, diseases and weeds are of food for which the carbon footprint has already been committed and so crop protection becomes an even greater concern. The rapidly increasing global need for food and the aggravation of associated problems by the effects of climate change create a need for new and sustainable crop protection. The overall requirement for sustainability is to remove seasonal inputs, and consequently all crop protection will need to be delivered via the seed or other planting material. Although genetic modification (GM) has transformed the prospects of sustainable crop protection, considerably more development is essential for the realisation of the full potential of GM and thereby consumer acceptability. Secondary plant metabolism offers wider and perhaps more robust new crop protection via GM and can be accomplished without associated yield loss because of the low level of photosynthate diverted for plant defence by secondary metabolism. Toxic mechanisms can continue to be targeted but exploiting non‐toxic regulatory and signalling mechanisms should be the ultimate objective. There are many problems facing these proposals, both technical and social, and these are discussed but it is certainly not possible to stay where we are in terms of sustainability. The evidence for success is mounting and the technical opportunities from secondary plant metabolism are discussed here. © 2019 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Plants can alter nutritional availability, structure, and chemistry of the soil they grow in. These soil changes can positively or negatively influence the growth and metabolism of other plants that co-occur or grow later in the conditioned soil. Plant-soil feedbacks could affect community interactions and dynamics but also be applied in sustainable agriculture to promote plant growth and resistance to pests. In this study, we use a maize companion cropping system, commonly known as “push-pull,” as a model to investigate soil-mediated effects of functional biodiversity, on maize plant growth, and resistance against insect herbivores. We grew maize in soils collected from push-pull (polyculture) and non-push-pull (monoculture) fields. We evaluated maize performance by measuring plant growth, as well as resistance traits (herbivore oviposition and larval feeding, production of defense-related volatile, and non-volatile secondary defense metabolites). Maize plants grown in soil conditioned by push-pull companion cropping had a higher growth rate compared to those grown in soil from non-push-pull monoculture fields. In addition, soil from push-pull fields induced a constitutively higher and qualitatively different emission of volatile organic compounds than soil from non-push-pull fields. Moreover, secondary defense metabolites such as 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one (DIMBOA), were produced in larger quantities in plants grown in soil from push-pull fields compared to those from monoculture fields. These soil-mediated alterations in plant secondary metabolism were associated with reduced herbivory by larvae of the stemboring pest Chilo partelllus. This study provides novel evidence that plant-soil feedbacks can affect plant metabolism, growth, and resistance to pests. The observed soil-mediated effects on maize plant secondary metabolism can be viewed as emergent properties of plant community composition as well as a potent mechanism of associational resistance. In addition, these soil-conditioning effects provide a novel pest control mechanism of push-pull companion cropping.

Maize (Zea mays L.) production is constrained in Ghana by declining soil fertility, erratic rainfall and the recent fall armyworm invasion. We hypothesised that adopting push-pull farming practices would reduce infestation and damage of maize by fall armyworm, while increasing maize yield. We conducted field experiments at two sites over two cropping seasons to evaluate the effects of spatial arrangements of push-pull companion crops on fall armyworm infestations and grain yield of maize. The experiment was arranged in a split-plot design with variety (Abotem and Opeaburo) as the main plot and fall armyworm treatment options (1 row maize and 1 row Desmodium [conventional push-pull]; three maize rows before one row of Desmodium [modified push-pull]; synthetic chemical and no treatment [control]) as a subplot. Results showed that, regardless of location or maize variety, both conventional and spatially modified push-pull companion cropping significantly reduced fall armyworm infestations under all seasons, as compared with the control. The push-pull companion cropping systems reduced the mean maize damage score of fall armyworm by 168%, compared with the control. Additionally, both conventional and spatially modified push-pull companion cropping significantly increased maize grain and biomass yield by 46.80% and 51.11%, respectively, irrespective of the maize variety compared with the control. The mean damage score, biomass and grain yield of conventional push-pull and modified push-pull were not significantly different. The fall armyworm infestation was decreased by 14.61% in the major season compared with the minor cropping season. This study provides novel evidence of the effectiveness of push-pull farming practice in reducing fall armyworm infestation and damage, and in increasing maize yield in Ghana, which has a different ecosystem to East Africa, where push-pull was developed. Further, it provides critical evidence of the effectiveness of a spatial modification of the push crop in relation with the main crop against the fall armyworm.

Low levels of nitrogen (N) and phosphorus (P) in soils in sub-Saharan Africa (SSA) limit maize (Zea mays) production in smallholder farms. We tested the hypothesis that desmodium (Desmodium intortum (Mill.) Urb.), a fodder legume, and food legumes commonly grown with maize in Western Kenya avail N and P and improve the performance of maize in intercrops. We measured available N and P in 15 cm topsoil at 4, 8 and 12 weeks after planting (WAP), and corresponding maize shoot weight in three seasons: 2017 long rains (LR), 2017 short rains (SR), and 2018 LR at Thomas Odhiambo Campus of icipe at Mbita Point in western Kenya. Treatments were additive 1:1 maize-legume intercrops; maize-bean (Phaseolus vulgaris L.), maize-cowpea (Vigna unguiculata (L.) Walp.), maize-crotalaria (Crotalaria ochroleuca G. Don), maize-desmodium, maize-green gram [Vigna radiata (L.) Wilczek] and maize-groundnut (Arachis hypogaea L.), and maize monocrop as a control, replicated four times in a complete randomized design. This experiment was established in 2003 and treatments were repeated every season on the same plot (for 31 seasons up to 2018 LR). At the beginning (year 2003), experimental plots were infested with 100 g of striga seeds per 250 g soil. Across the three last seasons corresponding to this study, we observed an increase in available N in maize-desmodium plots compared to maize monocrop plots. Available P measured at 4, 8 and 12 WAP in 2017 SR and at 4 WAP in 2018 LR was higher in maize-desmodium than in maize monocrop at the same sampling times (P

Lepidopterous stemborers, and parasitic striga weeds belonging to the family Orobanchaceae, attack cereal crops in sub-Saharan Africa causing severe yield losses. The smallholder farmers are resource constrained and unable to afford expensive chemicals for crop protection. The push–pull technology, a chemical ecology- based cropping system, is developed for integrated pest and weed management in cereal–livestock farming systems. Appropriate plants were selected that naturally emit signaling chemicals (semiochemicals). Plants highly attractive for stemborer egg laying were selected and employed as trap crops (pull), to draw pests away from the main crop. Plants that repelled stemborer females were selected as intercrops (push). The stemborers are attracted to the trap plant, and are repelled from the main cereal crop using a repellent intercrop (push). Root exudates of leguminous repellent intercrops also effectively control the parasitic striga weed through an allelopathic mechanism. Their root exudates contain flavonoid compounds some of which stimulate germination of Striga hermonthica seeds, such as Uncinanone B, and others that dramatically inhibit their attachment to host roots, such as Uncinanone C and a number of di-C-glycosylflavones (di-CGFs), resulting in suicidal germination. The intercrop also improves soil fertility through nitrogen fixation, natural mulching, improved biomass, and control of erosion. Both companion plants provide high value animal fodder, facilitating milk production and diversifying farmers’ income sources. The technology is appropriate to smallholder mixed cropping systems in Africa. Adopted by about 125,000 farmers to date in eastern Africa, it effectively addresses major production constraints, significantly increases maize yields, and is economical as it is based on locally available plants, not expensive external inputs.

Production of maize in western Kenya is severely constrained by the parasitic weed striga. Although productivity of maize can be improved through adoption of improved varieties, adoption of such varieties remains low in the region, as the majority of smallholder farmers still grow unimproved open-pollinated varieties (landraces). The performance of two improved hybrid varieties was evaluated against six landraces in striga-infested soils in western Kenya. The varieties were planted in plots under natural striga infestation and were supplemented with pot experiments under artificial infestation. Striga emergence was lower in landraces than in the hybrid varieties in both field and pot experiments. Similarly, height of maize plants at harvest and grain yields were higher in the landraces than in the hybrids. After three continuous cropping seasons, in all treatments, striga seedbank density increased two to seven times. Seedbank increase was higher with hybrids and two of the landraces, ‘Rachar' and ‘Endere'. These results provide an insight into the potential role landraces could play in efforts toward an integrated management approach for striga in smallholder cropping systems. They also highlight the need to develop hybrid maize lines with local adaptation to biotic constraints, specifically striga.

Push-pull is one of the sustainable intensification technologies for the control of stem-borers, striga weed and fall armyworm. Even though the effectiveness of push-pull in addressing these constraints has been evaluated under different agro-ecological conditions and on research stations, performance of the technology relative to other common maize-based cropping systems in farmers’ fields and the impact of the push-pull age is not yet understood. We hypothesized that, a) maize grain yield and aboveground biomass from push-pull system is higher than other common maize farming systems; b) duration of use of push-pull, and climatic conditions have an influence on its efficacy; and c) the presence of legumes in maize farms positively affects system performance. We compared maize grain yield, aboveground biomass and striga emergence of push-pull system with common maize farming systems: (1) maize monocrop (2) maize-bean intercrop, (3) maize-cowpea intercrop, (4) maize-green gram intercrop, and (5) maize-groundnut intercrop in 45 farms in three contrasting sites (Vihiga, Siaya and Bondo) in western Kenya. Push-pull increased maize grain yield by 2.33 and 1.77 Mg ha−1 in Vihiga in 2017 long and short rains, and 2.15 Mg ha−1 in Bondo in 2018 long rains, and aboveground biomass by between 2.84 Mg ha−1 in Vihiga in 2018 long rains and 8.94 Mg ha−1 in Bondo in 2018 long rains. Striga emergence declined in push-pull systems by up to 100 % and its performance varied with sites and seasons. Farms that had practiced push-pull for less than 2 years had a higher number of striga than farms which had practiced it for more than 2 years for the first season; the number decreased and was similar to that for farms which had practiced push-pull for above 2 years in the two subsequent seasons. Farms with legumes had similar maize grain and aboveground biomass as maize monocrop in all sites and seasons, and higher number of striga in Siaya in 2017 short rains and 2018 long rains, and Vihiga in 2018 long rains. These findings show that push-pull is similar or superior to other maize farming systems in terms of maize grain and biomass production; and that while its performance is influenced by agro-ecological conditions, its efficacy in controlling striga increases over time, and its productivity is not compromised over time on the same farm.

Push-pull, a novel approach for integrated management of insect pests, weed and soil fertility, was developed through the exploitation of chemical ecology and agro-biodiversity to address agricultural constraints facing millions of resource-poor African farmers. The technology was developed by selecting appropriate plants that naturally emit signalling chemicals (semiochemicals) and influence plant-plant and insect-plant interactions. Plants highly attractive for egg laying by lepidopteran cereal stemborer pests were selected and employed as trap crops, to draw pests away from the main cereal crops. Among these, Pennisetum purpureum produced significantly higher levels of volatile cues (stimuli), used by gravid stem borer females to locate host plants, than maize (Zea mays) or sorghum (Sorghum bicolor). Despite its attractiveness to stemborer moths, P. purpureum supported minimal survival of the pests’ immature stages. Plants that repelled stem borer moths, notably Melinis minutiflora and forage legumes in the genus Desmodium, were selected as intercrops, which also attracted natural enemies of the pests through emission of (E)-β-ocimene and (E)-4,8-dimethyl-1,3,7-nonatriene. Desmodium intercrop suppressed parasitic weed, Striga hermonthica, through an allelopathic mechanism. Their root exudates contain novel flavonoid compounds which stimulate suicidal germination of S. hermonthica seeds and dramatically inhibit its attachment to the host roots. We identified and selected new drought- and temperature-tolerant trap [Brachiaria ( B. brizantha × B. ruziziensis ) cv. mulato] and intercrop plants (Desmodium, e.g. D. intortum) suitable for drier agroecologies. The new trap and intercrop plants also have appropriate chemistry in controlling stemborers, a new invasive pest, fall armyworms and parasitic striga weeds. Opportunities for semiochemical delivery by companion plants, including plant-plant signalling and early herbivory alert, are explored for developing future smart integrated pest management (IPM) strategies.

The recent discovery by Advanced LIGO and Advanced Virgo of a gravitational wave signal from a binary neutron star inspiral has enabled tests of general relativity (GR) with this new type of source. This source, for the first time, permits tests of strong-field dynamics of compact binaries in presence of matter. In this paper, we place constraints on the dipole radiation and possible deviations from GR in the post-Newtonian coefficients that govern the inspiral regime. Bounds on modified dispersion of gravitational waves are obtained; in combination with information from the observed electromagnetic counterpart we can also constrain effects due to large extra dimensions. Finally, the polarization content of the gravitational wave signal is studied. The results of all tests performed here show good agreement with GR., Comment: 15 pages, 4 figures. Matches journal submission

Napier grass stunt (NGS) disease is a serious disease of the most important fodder crop in East Africa. The disease is caused by a phytoplasma, ‘Candidatus Phytoplasma oryzae’, a cell wall-less bacterium belonging to the 16SrXI group, in the class Mollicutes. The disease affects Napier grass causing up to 100% crop loss in infested farms. Despite the absence of a commercially available, effective control method, several techniques have been attempted by farmers to support the integrated management of NGS disease in the affected regions. This chapter reviews various methods used by farmers to control the disease in Kenya, Tanzania and Uganda. We also propose suggestions that could be used to curb the spread of the disease to regions not yet reached by the pathogen.

Plants have evolved intricate defence strategies against herbivore attack which can include activation of defence in response to stress-related volatile organic compounds (VOCs) emitted by neighbouring plants. VOCs released by intact molasses grass (Melinis minutiflora), have been shown to repel stemborer, Chilo partellus (Swinhoe), from maize and enhance parasitism by Cotesia sesamiae (Cameron). In this study, we tested whether the molasses grass VOCs have a role in plant-plant communication by exposing different maize cultivars to molasses grass for a 3-week induction period and then observing insect responses to the exposed plants. In bioassays, C. partellus preferred non-exposed maize landrace plants for egg deposition to those exposed to molasses grass. Conversely, C. sesamiae parasitoid wasps preferred volatiles from molasses grass exposed maize landraces compared to volatiles from unexposed control plants. Interestingly, the molasses grass induced defence responses were not observed on hybrid maize varieties tested, suggesting that the effect was not simply due to absorption and re-emission of VOCs. Chemical and electrophysiological analyses revealed strong induction of bioactive compounds such as (R)-linalool, (E)-4,8-dimethyl-1,3,7-nonatriene and (E,E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene from maize landraces exposed to molasses grass volatiles. Our results suggest that constitutively emitted molasses grass VOCs can induce direct and indirect defence responses in neighbouring maize landraces. Plants activating defences by VOC exposure alone could realize enhanced levels of resistance and fitness compared to those that launch defence responses upon herbivore attack. Opportunities for exploiting plant-plant signalling to develop ecologically sustainable crop protection strategies against devastating insect pests such as stemborer C. partellus are discussed.

The invasion by Striga in most cereal crop fields in Africa has posed a significant threat to food security and has caused substantial socioeconomic losses. Hyperspectral remote sensing is an effective means to discriminate plant species, providing possibilities to track such weed invasions and improve precision agriculture. However, essential baseline information using remotely sensed data is missing, specifically for the Striga weed in Africa. In this study, we investigated the spectral uniqueness of Striga compared to other co-occurring maize crops and weeds. We used the in-situ FieldSpec® Handheld 2™ analytical spectral device (ASD), hyperspectral data and their respective narrow-band indices in the visible and near infrared (VNIR) region of the electromagnetic spectrum (EMS) and four machine learning discriminant algorithms (i.e. random forest: RF, linear discriminant analysis: LDA, gradient boosting: GB and support vector machines: SVM) to discriminate among different levels of Striga (Striga hermonthica) infestations in maize fields in western Kenya. We also tested the utility of Sentinel-2 waveband configurations to map and discriminate Striga infestation in heterogenous cereal crop fields. The in-situ hyperspectral reflectance data were resampled to the spectral waveband configurations of Sentinel-2 using published spectral response functions. We sampled and detected seven Striga infestation classes based on three flowering Striga classes (low, moderate and high) against two background endmembers (soil and a mixture of maize and other co-occurring weeds). A guided regularized random forest (GRRF) algorithm was used to select the most relevant hyperspectral wavebands and vegetation indices (VIs) as well as for the resampled Sentinel-2 multispectral wavebands for Striga infestation discrimination. The performance of the four discriminant algorithms was compared using classification accuracy assessment metrics. We were able to positively discriminate Striga from the two background endmembers i.e. soil and co-occurring vegetation (maize and co-occurring weeds) based on the few GRRF selected hyperspectral vegetation indices and the GRRF selected resampled Sentinel-2 multispectral bands. RF outperformed all the other discriminant methods and produced the highest overall accuracy of 91% and 85%, using the hyperspectral and resampled Sentinel-2 multispectral wavebands, respectively, across the four different discriminant models tested in this study. The class with the highest detection accuracy across all the four discriminant algorithms, was the “exclusively maize and other co-occurring weeds” (>70%). The GRRF reduced the dimensionality of the hyperspectral data and selected only 9 most relevant wavebands out of 750 wavebands, 6 VIs out of 15 and 6 out of 10 resampled Sentinel-2 multispectral wavebands for discriminating among the Striga and co-occurring classes. Resampled Sentinel-2 multispectral wavebands 3 (green) and 4 (red) were the most crucial for Striga detection. The use of the most relevant hyperspectral features (i.e. wavebands and VIs) significantly (p ≤ 0.05) increased the overall classification accuracy and Kappa scores (±5% and ±0.2, respectively) in all the machine learning discriminant models. Our results show the potential of hyperspectral, resampled Sentinel-2 multispectral datasets and machine learning discriminant algorithms as a tool to accurately discern Striga in heterogenous maize agro-ecological systems.

Grasses in the genus Urochloa, commonly known as brachiaria, are grown as forage crops in sub-Saharan Africa, with some genotypes being used in management of insect pests. However, spider mite, Oligonychus trichardti Meyer (Acari: Tetranychidae), has recently been reported as its major pest in the region. We evaluated 18 brachiaria genotypes to identify sources of resistance to O. trichardti, and to determine their adaptability to different environments in western Kenya. Response to artificial infestation with O. trichardti was evaluated under controlled conditions in a screenhouse while adaptability to different environments and field resistance to mites was evaluated in three locations for two cropping seasons in 2016 and 2017 under farmers’ conditions. The parameters evaluated as indicators of resistance to pest damage included leaf damage, chlorophyll content reduction, plant height, leaf area, number of tillers and shoot biomass. Rainfall played a role in reducing mite infestation and increasing biomass yield of the genotypes. Significant correlations between parameters were only observed between leaf damage and yield (r = -0.50), and leaf damage and chlorophyll loss (r = 0.85). The cultivar superiority index (Pi) ranked Xaraes, Piata, ILRI 12991 and ILRI 13810 as reliable genotypes that combined moderate resistance to the mite (Pi ≤ 48.0) and high biomass yield (Pi ≤ 8.0). Since this is the first documentation of interactions between O. trichardti and different brachiaria genotypes, we propose these genotypes as potential candidates for improved forage yields in areas prone to O. trichardti infestation in Africa.

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.

Graphical abstract Drought tolerant Desmodium species, when mature, produce root exudates that inhibit Striga parasitism and which comprise a range of di-C-glycosylflavones., Highlights • Root exudates from drought tolerant Desmodium spp. were analysed by HPLC and LCMS. • Compounds were identified as di-C-glycosylflavones using standards. • After 4 months, exudates from drought tolerant species were similar to each other. • Exudates possessed Striga inhibitory properties in pot experiments in all cases. • Desmodium spp. identified are active against Striga in semi-arid field conditions., Plants from the genus Desmodium, in particular D. uncinatum, are used on sub-Saharan small-holder farms as intercrops to inhibit parasitism of cereal crops by Striga hermonthica and Striga asiatica via an allelopathic mechanism. The search for Desmodium species which are adapted to more arid conditions, and which show resilience to increased drought stress, previously identified D. intortum, D. incanum and D. ramosissimum as potential drought tolerant intercrops. Their potential as intercrops was assessed for resource poor areas of rain-fed cereal production where drought conditions can persist through normal meteorological activity, or where drought may have increasing impact through climate change. The chemical composition of the root exudates were characterised and the whole exudate biological activity was shown to be active in pot experiments for inhibition of Striga parasitism on maize. Furthermore, rain fed plot experiments showed the drought tolerant Desmodium intercrops to be effective for Striga inhibition. This work demonstrates the allelopathic nature of the new drought tolerant intercrops through activity of root exudates and the major compounds seen in the exudates are characterised as being C-glycosylflavonoid. In young plants, the exudates show large qualitative differences but as the plants mature, there is a high degree of convergence of the C-glycosylflavonoid exudate chemical profile amongst active Desmodium intercrops that confers biological activity. This defines the material for examining the mechanism for Striga inhibition.

Production of cereals, the main staple and cash crops for millions of farmers in sub-Saharan Africa (SSA) is severely constrained by parasitic striga weed Striga hermonthica, stemborers and poor soil fertility. A companion cropping system known as ‘push–pull’ overcomes these constraints while providing additional soil fertility and forage grass benefits to smallholder farmers. To ensure the technology's long-term sustainability in view of the current and further potential aridification as a consequence of climate change, drought-tolerant crops, Brachiaria cv mulato (border crop) and greenleaf desmodium (intercrop), have been identified and incorporated into a ‘climate-adapted push–pull’. The aims of the current study were to evaluate effectiveness of the new system (i) in integrated control of striga and stemborer pests and (ii) in improving maize grain yields, and to evaluate farmers’ perceptions of the technology to assess potential for further adoption. 395 farmers who had adopted the technology in drier areas of Kenya, Uganda and Tanzania were randomly selected for the study. Each farmer had a set of two plots, a climate-adapted push–pull and a maize monocrop. Seasonal data were collected in each plot on the number of emerged striga plants, percentage of maize plants damaged by stemborers, plant height and grain yields. Similarly, farmers’ perceptions of the benefits of the technology were assessed using a semi-structured questionnaire. There were highly significant reductions in striga and stemborer damage to maize plants in the climate-adapted push–pull compared to the maize monocrop plots: striga levels were 18 times lower and stemborer levels were 6 times lower. Similarly, maize plant height and grain yields were significantly higher. Mean yields were 2.5 times higher in companion planting plots. Farmers rated the climate-adapted push–pull significantly superior in reducing striga infestation and stemborer damage rates, and in improving soil fertility and maize grain yields. These results demonstrate that the technology is effective in controlling both weeds and pests with concomitant yield increases under farmers’ conditions. It thus provides an opportunity to improve food security, stimulate economic growth, and alleviate poverty in the region while making agriculture more resilient to climate change.

Plant defence responses to insect oviposition, including tritrophic interactions with natural enemies of herbivores, have rarely been targeted in crop breeding programmes. Emission of herbivore induced plant volatiles (HIPVs) that attract natural enemies early on at the egg-laying stage of herbivore attack could provide timely biological control of pests and deter subsequent oviposition. This is needed in an agroecological context where the third trophic level often does not keep pace with the growth rate of pests. Our very recent data, using maize as an example, show that herbivore egg induced volatile emission is very rare in commercial hybrids but common in farmer selected landraces. Strategies for crop genetic improvement to enhance such responses to insect attack are considered.

1. Africa faces serious challenges in feeding its rapidly growing human\ud population owing to the poor productivity of maize and sorghum, the most important\ud staple crops formillions of smallholder farmers in the continent,with yields being among\ud the lowest in the world.\ud 2. A complex of lepidopterous stemborers attack cereals in Africa. However, their\ud effective control is difficult, largely as a result of the cryptic and nocturnal habits of\ud moths, and protection provided by host stem for immature pest stages.Moreover, current\ud control measures are uneconomical and impractical for resource-poor farmers.\ud 3. An ecological approach, based on companion planting, known as ‘push–pull’,\ud provides effective management of these pests, and involves combined use of inter- and\ud trap cropping systems where stemborers are attracted and trapped on trap plants with\ud added economic value (‘pull’), and are driven away from the cereal crop by antagonistic\ud intercrops (‘push’).\ud 4. Novel defence strategies inducible by stemborer oviposition have recently been\ud discovered, leading to the attraction of egg and larval parasitoids, in locally adapted\ud maize lines but not in elite hybrids. We also established that landscape complexity did\ud not improve the ecosystem service of biological control, but rather provided a disservice\ud by acting as a ‘source’ of stemborer pests colonising the crop.\ud 5. Here we review and provide new data on the direct and indirect effects of the\ud push–pull approach on stemborers and their natural enemies, including the mechanisms\ud involved, and highlight opportunities for exploiting intrinsic plant defences and natural\ud ecosystem services in pest management in smallholder farming systems in Africa.

Napier or Elephant grass (Pennisetum purpureum), the most important livestock fodder crop in East Africa, is under threat from Napier grass stunt (NGS) disease. This disease is caused by a phytoplasma, which is transmitted by the leafhopper, Maiestas banda (Hemiptera: Cicadellidae). After inoculation, the disease rapidly infects the whole plant causing extensive damage to Napier grass plants. There is therefore a need to develop an integrated management approach for the disease. A survey was conducted in three East African countries (Kenya, Uganda and Tanzania) during which 198 farmers were interviewed using semi-structured questionnaires. The questionnaire addressed the prevalence of NGS, source of planting material and Napier grass cultivars grown. Farmers were also questioned on how they perceived the severity of the disease, management options and on the knowledge of the existence of wild grass hosts of the disease and its vector. Disease prevalence in survey areas was expressed as a percentage of the total 198 fields assessed. Chi-square (χ2), F tests and one-way analysis of variance (ANOVA) were conducted to asses any differences between districts, gender and education levels with regards to the knowledge and perceptions of NGS in the three countries. The prevalence of NGS ranged from 33% in Uganda to 95.7% in Kenya with an average of 55.1%. Among the farmers interviewed, 49.5% were able to recognize NGS symptoms. Most farmers did not have effective management approaches for the disease but cited a variety of measures including roguing and introduction of alternative fodder grasses that could potentially form part of an integrated management approach for the disease. Sedge grass (Cyperus sp.) and Star grass (Cynodon dactylon) were listed by the respondents as the likely hosts of stunt diseases caused by phytoplasma. It has been long suspected that weeds could play a role in the spread of phytoplasma by acting both as reservoirs from which healthy plants could be re-infected and also as hosts for the vectors. Since there is no well-established control method for NGS, the majority of farmers uproot infected plants and replant with new ones to lower the infection pressure by providing fewer infected plants for vectors to feed on. This pinpoints the need for farmers' awareness and the need to develop resistant Napier grass cultivars as a management option.

Food security attainment in Africa has been hindered by poor yields of cereals that serve both as staple and cash crops for the majority of smallholder farmers. Among the various constraints responsible for lower yields are the parasitic weed Striga, and Stemborer pests whose control has remained a challenge. The International Centre of Insect Physiology and Ecology (icipe) with partners developed a novel conservation agricultural technology termed ‘push-pull’, based on companion cropping that effectively controls both constraints simultaneously. However, the effects of climate change threatened its expansion into drier areas where Striga is rapidly spreading. Further adaptation of the conventional (original) push-pull technology was thus achieved through identification and incorporation of drought tolerant companion crops, and the procedure termed ‘climate-smart’ push-pull technology. With maximum adoption of the adapted technology, food security in the drier agro-ecologies would be enhanced through increased cereal yields. Adoption, however, depends on how well technology dissemination is implemented. The objective of this study was to quantify the potential adoption and impact of climate-smart push-pull technology ex ante in order to plan for its wide scale dissemination. Using a sample of 898 respondents (360 in Kenya, 240 in Tanzania, 298 in Ethiopia), multinomial logit and marginal rate of return (MRR) methods were used to analyze the findings of the ex ante baseline survey. These showed a high potential for adoption of climate-smart push-pull as 87.8 % of the overall sample were willing to adopt; 92.1 % in Tanzania, 88.6 % in Ethiopia and 84.3 % in Kenya. Gender, perceptions of Striga severity, technology awareness and input market access were the most likely factors that would positively influence the decision to adopt (marginal effects 0.060, 0.010, 0.042, and 0.738 respectively). The MRR was 109.2 % for sorghum and 143.4 % for maize, implying an expected positive impact to the community should they adopt the technology.

A better understanding of the chemical cues employed by parasitoids to locate their herbivore hosts will contribute towards effective exploitation of parasitoids as biological control agents against damaging crop pests. The current study was conducted to establish key bioactive compounds mediating behavioural response in the parasitic wasp Cotesia sesamiae (Cameron, 1906) (Hymenoptera: Braconidae) by employing electrophysiological techniques and behavioural studies. Electroantennogram (EAG) recording with synthetic equivalents of herbivore-induced plant volatiles (HIPVs) using C. sesamiae confirmed that 13 compounds elicited electrophysiological activity. In an olfactometer bioassay, only (E)-4,8-dimethyl-1,3,7-nonatriene, (E)-β-farnesene, and (E,E)-4,8,-trimethyl-1,3,7-tridecatetraene elicited behavioural responses from the parasitoid when tested individually at a natural dose, while (R)-linalool and (E)-caryophyllene were attractive at the highest test dose. Other EAG-active HIPVs were not attractive either at lower or higher concentrations, suggesting their role as blend components rather than functioning as attractants by themselves. In contrast, nine-component synthetic HIPV blends formulated in the same ratio and concentration as in a natural sample was as attractive as the original headspace sample. By providing further insights into maize–stemborer–parasitoid tritrophic interactions, results from this study will help in selecting crop cultivars emitting appropriate HIPVs to attract natural enemies and perhaps repel damaging crop pests.