Classical survival analysis assumes all subjects will experience the event of interest, but in some cases, a portion of the population may never encounter the event. These survival methods further assume independent s...Classical survival analysis assumes all subjects will experience the event of interest, but in some cases, a portion of the population may never encounter the event. These survival methods further assume independent survival times, which is not valid for honey bees, which live in nests. The study introduces a semi-parametric marginal proportional hazards mixture cure (PHMC) model with exchangeable correlation structure, using generalized estimating equations for survival data analysis. The model was tested on clustered right-censored bees survival data with a cured fraction, where two bee species were subjected to different entomopathogens to test the effect of the entomopathogens on the survival of the bee species. The Expectation-Solution algorithm is used to estimate the parameters. The study notes a weak positive association between cure statuses (ρ1=0.0007) and survival times for uncured bees (ρ2=0.0890), emphasizing their importance. The odds of being uncured for A. mellifera is higher than the odds for species M. ferruginea. The bee species, A. mellifera are more susceptible to entomopathogens icipe 7, icipe 20, and icipe 69. The Cox-Snell residuals show that the proposed semiparametric PH model generally fits the data well as compared to model that assume independent correlation structure. Thus, the semi parametric marginal proportional hazards mixture cure is parsimonious model for correlated bees survival data.展开更多
Nairobi County experiences rapid industrialization and urbanization that contributes to the deteriorating state of air quality, posing a potential health risk to its growing population. Currently, in Nairobi County, m...Nairobi County experiences rapid industrialization and urbanization that contributes to the deteriorating state of air quality, posing a potential health risk to its growing population. Currently, in Nairobi County, most air quality monitoring stations use low-cost, inaccurate monitors prone to defects. The study’s objective was to map Nairobi County’s air quality using freely available remotely sensed imagery. The Air Pollution Index (API) formula was used to characterize the air quality from cloud-free Landsat satellite images i.e., Landsat 5 TM, Landsat 7 ETM+, and Landsat 8 OLI from Google Earth Engine. The API values were computed based on vegetation indices namely NDVI, TVI, DVI, and the SWIR1 and NIR bands on the QGIS platform. Qualitative accuracy assessment was done using sample points drawn from residential, industrial, green spaces, and traffic hotspot categories, based on a passive-random sampling technique. In this study, Landsat 5 API imagery for 2010 provided a reliable representation of local conditions but indicated significant pollution in green spaces, with recorded values ranging from -143 to 334. The study found that Landsat 7 API imagery in 2002 showed expected results with the range of values being -55 to 287, while Landsat 8 indicated high pollution levels in Nairobi. The results emphasized the importance of air quality factors in API calibration and the unmatched spatial coverage of satellite observations over ground-based monitoring techniques. The study recommends the recalibration of the API formula for characteristic regions, exploring newer satellite sensors like those onboard Landsat 9 and Sentinel 2, and involving key stakeholders in a discourse to develop a suitable Kenyan air quality index.展开更多
Quantitative headspace analysis of volatiles emitted by plants or any other living organisms in chemical ecology studies generates large multidimensional data that require extensive mining and refining to extract usef...Quantitative headspace analysis of volatiles emitted by plants or any other living organisms in chemical ecology studies generates large multidimensional data that require extensive mining and refining to extract useful information. More often the number of variables and the quantified volatile compounds exceed the number of observations or samples and hence many traditional statistical analysis methods become inefficient. Here, we employed machine learning algorithm, random forest (RF) in combination with distance-based procedure, similarity percentage (SIMPER) as preprocessing steps to reduce the data dimensionality in the chemical profiles of volatiles from three African nightshade plant species before subjecting the data to non-metric multidimensional scaling (NMDS). In addition, non-parametric methods namely permutational multivariate analysis of variance (PERMANOVA) and analysis of similarities (ANOSIM) were applied to test hypothesis of differences among the African nightshade species based on the volatiles profiles and ascertain the patterns revealed by NMDS plots. Our results revealed that there were significant differences among the African nightshade species when the data’s dimension was reduced using RF variable importance and SIMPER, as also supported by NMDS plots that showed S. scabrum being separated from S. villosum and S. sarrachoides based on the reduced data variables. The novelty of our work is on the merits of using data reduction techniques to successfully reveal differences in groups which could have otherwise not been the case if the analysis were performed on the entire original data matrix characterized by small samples. The R code used in the analysis has been shared herein for interested researchers to customise it for their own data of similar nature.展开更多
Survival analysis is a fundamental tool in medical science for time-to-event data. However, its application to colony organisms like bees poses challenges due to their social nature. Traditional survival models may no...Survival analysis is a fundamental tool in medical science for time-to-event data. However, its application to colony organisms like bees poses challenges due to their social nature. Traditional survival models may not accurately capture the interdependence among individuals within a colony. Frailty models, accounting for shared risks within groups, offer a promising alternative. This study evaluates the performance of semi-parametric shared frailty models (gamma, inverse normal, and positive stable-in comparison to the traditional Cox model using bees’ survival data). We examined the effect of misspecification of the frailty distribution on regression and heterogeneity parameters using simulation and concluded that the heterogeneity parameter was more sensitive to misspecification of the frailty distribution and choice of initial parameters (cluster size and true heterogeneity parameter) compared to the regression parameter. From the data, parameter estimates for covariates were close for the four models but slightly higher for the Cox model. The shared gamma frailty model provided a better fit to the data in comparison with the other models. Therefore, when focusing on regression parameters, the gamma frailty model is recommended. This research underscores the importance of tailored survival methodologies for accurately analyzing time-to-event data in social organisms.展开更多
The efficacy of aqueous and emulsifiable formulations of the fungus Metarhizium anisopliae isolate ICIPE78 was evaluated on the population density of Tetranychus urticae infesting common bean plants under screenhouse ...The efficacy of aqueous and emulsifiable formulations of the fungus Metarhizium anisopliae isolate ICIPE78 was evaluated on the population density of Tetranychus urticae infesting common bean plants under screenhouse and field conditions. Synthetic acaricide abamectin was included as a check. Bean plants were artificially infested with T. urticae and allowed to multiply. Three treatments were applied in the screenhouse and 1 treatment in field trials. Mite density was recorded 2 d before spraying and weekly postspraying. The number of pods per plant, number of seeds per pod, and the dry weight of seeds per plant were recorded only in the screenhouse trials. In both screenhouse and field trials, fungal formulations applied at the concentration of 108 conidia/mL and the aearicide reduced the population density of mites as compared to the controls. There were signif- icant differences in T. urticae population densities between the treatments at the various post-spraying sampling dates. In the screenhouse, the mite densities were near zero from 3-week postspraying in the treated leaves. At 4-week postspraying, there were no more leaves in the untreated control （T1） and in the control water ＋ Silwet-L77 （T2）. Fungal formulations were as effective as abamectin in reducing mite densities in both screenhouse and field experiments. There were significant differences in the production parameters during the 2 screenhouse trials, with fungal and abamectin treatments generally having the highest yield. Results of this study underline the potential of the M. anisopliae isolate ICIPE78 as an alternative to acaricides for T. urticae management.展开更多
Tomato (Lycopersicon esculentum) is one of the important vegetables in supplying vitamins, minerals and fiber to human diets worldwide. Its successful production in the tropics is, however, constrained by environmenta...Tomato (Lycopersicon esculentum) is one of the important vegetables in supplying vitamins, minerals and fiber to human diets worldwide. Its successful production in the tropics is, however, constrained by environmental variations especially under open field conditions. Two trials were conducted at the Horticulture Research and Teaching Field, Egerton University, Kenya to evaluate the effects of agricultural nets (agronets) herein called eco-friendly nets (EFNs) and floating row covers (FRCs) on microclimate modification, yield, and quality of tomato. A randomized complete block design with five replications was used. Tomato plants were grown under fine mesh EFN (0.4-mm pore diameter) cover, large mesh EFN (0.9-mm pore diameter) cover or FRC. The EFN and FRC were maintained either permanently closed or opened thrice a week from 9 am to 3 pm. Two open control treatments were used: unsprayed (untreated control) or sprayed with chemicals (treated control). The use of EFN or FRC modified the microclimate with higher temperatures, lower diurnal temperature ranges, and higher volumetric water content recorded compared with the controls. On the other hand, light quantity and photosynthetic active radiation were reduced by the use of EFN and FRC compared with the controls. The use of FRC and EFN resulted in more fruit and higher percent in marketable yield compared with open field production. Fruit quality at harvest was also significantly improved by the use of EFN and FRC. Fruits with higher total soluble solids (TSS), lower titratable acidity (TA), and higher sugar acid ratio were obtained in EFN and FRC treatments compared with the controls. Fruits harvested from EFN and FRC were also firmer compared with control fruits. These findings demonstrate the potential of EFN and FRC in modifying microclimate conditions and improving yields and quality of tomato under tropical field conditions.展开更多
Pollinators use multiple cues whilst foraging in eluding direct cues from flowers and in direct cues from other pollinators. The use of indirect social cues is common in social in sects, such as honeybees and bumblebe...Pollinators use multiple cues whilst foraging in eluding direct cues from flowers and in direct cues from other pollinators. The use of indirect social cues is common in social in sects, such as honeybees and bumblebees, where a social environment facilitates the ability to use such cues. Bumblebees use cues to forage on flowers according to previous foraging experiences. Flowers are an essential food source for pollinators but also pose a high risk of parasite infection through the shared use of flowers leading to parasite spillover. Nevertheless, bumblebees have evolved behavioral defense mechanisms to limit parasite infection by avoiding contaminated flowers. Mechanisms underlying the avoidance of contaminated flowers by bumblebees are poorly understood. Bumblebees were recorded having the choice to forage on non-contaminated flowers and flowers contaminated by a trypan osome gut parasite, Crithidia bombi. The use of different treatments with presence or absence of con specifics on both con taminated and non-contami nated flowers allowed to investigate the role of social visual cues on their pathogen avoidance behavior. Bumblebees are expected to use social visual cues to avoid contaminated flowers. Our study reveals that the presence of a con specific on flowers either con taminated or not does not help bumblebee foragers avoiding contaminated flowers. Nevertheless, bumblebees whereas gaining experie nee tend to avoid their con specific when placed on contami nated flower and copy it whe n on the non-contami nated flower. Our experime nt suggests a detrime ntal impact of floral see nt on disease avoidanee behavior.展开更多
Dose-response studies in arthropod research usually involve observing and collecting successive information at different times on the same group of insects exposed to different concentrations of stimulus. When the sam...Dose-response studies in arthropod research usually involve observing and collecting successive information at different times on the same group of insects exposed to different concentrations of stimulus. When the same measure is collected repeatedly over time, the data become correlated and Probit Analysis technique which is the standard method in analyzing bioassay experiments data cannot be used. Lethal time is estimated when the speed of kill is of interest since mortality varies over time. We evaluate a complementary approach, repeated measures logistic regression using Generalized Estimating Equations (GEE), for lethal time determination in mosquito dose response. Mortality data from anopheles larva exposed to 3 botanical extracts (B,C,E) at 4 concentration levels: 500 mg/ml, 250 mg/ml, 50 mg/ml and 12.5 mg/ml were used. The result shows the estimated LT50 values with concentration 500 mg/ml being the most virulent chemical for extract B (LT50 = 10.3 hrs), C (LT50 = 7.2 hrs) and E (LT50 = 10.3 hrs). The least virulent chemical was concentration 12.5 mg/ml for extract B (LT50 = 52.1 hrs), C (LT50 = 70.7 hrs) and E (LT50 = 55.0 hrs). We conclude that repeated measures of logistic regression via GEE can be used as a tool to estimate LT50 more effectively in repeated measures of arthropod data.展开更多
Lepidopteran stem borers are the most damaging pests of maize in Sub-Saharan Africa. Despite the growing importance of maize in the forest zone of Democratic Republic of Congo, no data is available regarding stem bore...Lepidopteran stem borers are the most damaging pests of maize in Sub-Saharan Africa. Despite the growing importance of maize in the forest zone of Democratic Republic of Congo, no data is available regarding stem borer pest species present and their relative importance. It is thus important to gather information likely to guide future research in this area. This study was undertaken to catalogue stem borer pest species identity and assess their relative infestation levels on maize. Surveys were carried out in wild and cultivated habitats in Kisangani. Five species were collected on maize, i.e., Sesamia calamistis Hampson （1910）, Eldana saccharina Walker （1865）, Busseola fusca Fuller （1901）, Chilo sp. Strand （1913）, and Mussidia nigrivenella Ragonot （1888）. In the wild habitats, Poenoma serrata Hampson, B. fusca and S. calamistis were collected on Pennisetum purpureum whereas Chilo sp. was collected on Panicum maximum. Our results suggest that P. maximum might affect the population dynamics of Chilo sp. whereas P. purpureum is expected not to influence the population dynamics of other stem borers owing to its scarcity in the interior of the forest.展开更多
<b><span style="font-family:Verdana;">Background:</span></b><i><span style="font-family:Verdana;"> Plasmodium falciparum</span></i><span style=&qu...<b><span style="font-family:Verdana;">Background:</span></b><i><span style="font-family:Verdana;"> Plasmodium falciparum</span></i><span style="font-family:;" "=""><span style="font-family:Verdana;"> (</span><i><span style="font-family:Verdana;">Pf</span></i><span style="font-family:Verdana;">) resistance to antimalarial drugs is a major impediment to malaria control. The </span><i><span style="font-family:Verdana;">Pf</span></i><span style="font-family:Verdana;">.</span><i><span style="font-family:Verdana;">Kelch 13</span></i><span style="font-family:Verdana;"> (</span><i><span style="font-family:Verdana;">PfK13</span></i><span style="font-family:Verdana;">) gene has been largely reported to be associated with artemisinin resistance. However, recent studies have shown artemisinin resistance without </span><i><span style="font-family:Verdana;">Kech13 </span></i><span style="font-family:Verdana;">mutations suggesting the implication of others genes in artemisinin resistance. In this current study, we focused on mutations in </span><i><span style="font-family:Verdana;">Pf.</span></i><span style="font-family:Verdana;">actin-binding protein coronin, </span><i><span style="font-family:Verdana;">Pf.</span></i><span style="font-family:Verdana;">c</span><span><span style="font-family:Verdana;">ysteine</span><i> </i><span style="font-family:Verdana;">desulfurase and </span><i><span style="font-family:Verdana;">Pf</span></i><span style="font-family:Verdana;">.plasmepsin 2 gene, three putative candidates recently were reported to be</span><span style="color:red;"> </span><span style="font-family:Verdana;">involved in artemisinin, lumefantrine and piperaquine resistance respectively. </span><b><span style="font-family:Verdana;">Method: </span></b><span style="font-family:Verdana;">Archived blood samples previously collected from asymptomatic school children from December 2016 to October 2018 were used in this study. Genomic DNA was extracted using ISOL</span></span><span style="font-family:Verdana;">ATE II Genomic DNA kit. A展开更多
The report sets out to summarize the past and current situation regarding the practice of biologicalcontrol inrelationtothe use and exchange of genetic resources relevant for BCAs.It considers the twomain categories o...The report sets out to summarize the past and current situation regarding the practice of biologicalcontrol inrelationtothe use and exchange of genetic resources relevant for BCAs.It considers the twomain categories of biological control:classical and augmentative.Allowing access to BCAs for use inanother country imposes no risk of liability to the source country.Local scientific knowledge abouthabitats,fauna andflora,can be展开更多
The development of hosts that are resistant and evaluation of botanical extracts to H. armigera Hübner (Lepidoptera: Noctuidae) is crucial for sustainable management, yet very limited in Ethiopia. Therefore, this...The development of hosts that are resistant and evaluation of botanical extracts to H. armigera Hübner (Lepidoptera: Noctuidae) is crucial for sustainable management, yet very limited in Ethiopia. Therefore, this study was done to identify alternative methods to insecticide control through host consumption study and botanical extracts. The performance of third-fifth larval stages of H. armigera on three host plant varieties including chickpea, tomato and faba bean and botanical extracts against the third larval instars and oviposition deterrence was studied under laboratory condition (22°C ± 2°C, 55% ± 5% RH, 12:12 L: D photoperiod). Significant differences were found in the efficiency of conversion of ingested food (ECI%) (F = 80.06;df = 6, 2;p H. armigera reared on the three host plant varieties of the whole larval instars. The minimum relative consumption rate (RCR) (11.271 ± 0.328) and maximum approximate digestibility (AD) (177.9 ± 1.928) values of the whole larval instars were on Dagaga and Koshari, respectively. The values of relative growth rate (RGR), ECI% and ECD% of the whole larval instars were highest on chickpea varieties and lowest on tomato Koshari. Among chickpea varieties, Habru was relatively resistant to larval instars of H. armigera. Botanical extracts at 50% neem oil (NO), 5% birbira seed extract (BSE) and 5% neem seed extract (NSE) (18.4%) resulted superior in larval mortality however, statistically not different. At both 5% and 2.5% concentration level of botanical extracts the minimum larval mortality was recorded from neem leaf extract (NLE). Maximum numbers of eggs were laid on control treatments and the minimum eggs were on 5% BSE. The deterrent effect of 50% neem oil was stronger (ODI = 17.66%) than that of 5% BSE (ODI = 14%) which is statistically similar value with 5% NSE (ODI = 13%). In conclusion, the result indicated that use of Habru chickpea variety with 50% NO was very effective in controlling both the larvae and deterring the adults of H. armigera from egg lying. These展开更多
In recent years, numerous actions for sustainable exploitation of forest resources have been undertaken, but few deal with commercialization of forest insects. Several tree based insect products, like wild silk, can b...In recent years, numerous actions for sustainable exploitation of forest resources have been undertaken, but few deal with commercialization of forest insects. Several tree based insect products, like wild silk, can be linked with forest conservation activities to provide livelihood services of different economic scales to forest dependent people. African wild silkmoth, Argema mimosae Boisduval, is one of the forest insects, a moth in the family of Saturniidae producing wild silk, but there is need for definite procedures for extracting silk fibre from its cocoons. This study evaluated physical characteristics of the A. mimosae cocoons and outlined a procedure to extract viable silk fibre for use in silk industry. Cocoons of the A. mimosae were collected from natural forest of Arabuko-Sokoke, Kenya （3020＇ S, 39055＇ E）, and others obtained by semi-captive rearing of the silkmoth larvae. The cocoons of A mimosae were described to be silvery in colour, tough and thick with distinctive perforations on the surface and a prominent valve-like opening with loose filaments at one end. The study recorded 120 min as the optimum boiling time for the cocoons to yield silvery brown silk floss using sodium carbonate （Na2CO3） as the degumming agent. Cocoons boiled in distilled water could not be deflossed into floss, but remained hard and intact, as compared with those of the control, Bombyx mori. This reveals that A. mimosae cocoons can be processed for natural silk fibre production and offer communities adjacent to forests an excellent opportunity to engage in production of natural wild silk.展开更多
文摘Classical survival analysis assumes all subjects will experience the event of interest, but in some cases, a portion of the population may never encounter the event. These survival methods further assume independent survival times, which is not valid for honey bees, which live in nests. The study introduces a semi-parametric marginal proportional hazards mixture cure (PHMC) model with exchangeable correlation structure, using generalized estimating equations for survival data analysis. The model was tested on clustered right-censored bees survival data with a cured fraction, where two bee species were subjected to different entomopathogens to test the effect of the entomopathogens on the survival of the bee species. The Expectation-Solution algorithm is used to estimate the parameters. The study notes a weak positive association between cure statuses (ρ1=0.0007) and survival times for uncured bees (ρ2=0.0890), emphasizing their importance. The odds of being uncured for A. mellifera is higher than the odds for species M. ferruginea. The bee species, A. mellifera are more susceptible to entomopathogens icipe 7, icipe 20, and icipe 69. The Cox-Snell residuals show that the proposed semiparametric PH model generally fits the data well as compared to model that assume independent correlation structure. Thus, the semi parametric marginal proportional hazards mixture cure is parsimonious model for correlated bees survival data.
文摘Nairobi County experiences rapid industrialization and urbanization that contributes to the deteriorating state of air quality, posing a potential health risk to its growing population. Currently, in Nairobi County, most air quality monitoring stations use low-cost, inaccurate monitors prone to defects. The study’s objective was to map Nairobi County’s air quality using freely available remotely sensed imagery. The Air Pollution Index (API) formula was used to characterize the air quality from cloud-free Landsat satellite images i.e., Landsat 5 TM, Landsat 7 ETM+, and Landsat 8 OLI from Google Earth Engine. The API values were computed based on vegetation indices namely NDVI, TVI, DVI, and the SWIR1 and NIR bands on the QGIS platform. Qualitative accuracy assessment was done using sample points drawn from residential, industrial, green spaces, and traffic hotspot categories, based on a passive-random sampling technique. In this study, Landsat 5 API imagery for 2010 provided a reliable representation of local conditions but indicated significant pollution in green spaces, with recorded values ranging from -143 to 334. The study found that Landsat 7 API imagery in 2002 showed expected results with the range of values being -55 to 287, while Landsat 8 indicated high pollution levels in Nairobi. The results emphasized the importance of air quality factors in API calibration and the unmatched spatial coverage of satellite observations over ground-based monitoring techniques. The study recommends the recalibration of the API formula for characteristic regions, exploring newer satellite sensors like those onboard Landsat 9 and Sentinel 2, and involving key stakeholders in a discourse to develop a suitable Kenyan air quality index.
文摘Quantitative headspace analysis of volatiles emitted by plants or any other living organisms in chemical ecology studies generates large multidimensional data that require extensive mining and refining to extract useful information. More often the number of variables and the quantified volatile compounds exceed the number of observations or samples and hence many traditional statistical analysis methods become inefficient. Here, we employed machine learning algorithm, random forest (RF) in combination with distance-based procedure, similarity percentage (SIMPER) as preprocessing steps to reduce the data dimensionality in the chemical profiles of volatiles from three African nightshade plant species before subjecting the data to non-metric multidimensional scaling (NMDS). In addition, non-parametric methods namely permutational multivariate analysis of variance (PERMANOVA) and analysis of similarities (ANOSIM) were applied to test hypothesis of differences among the African nightshade species based on the volatiles profiles and ascertain the patterns revealed by NMDS plots. Our results revealed that there were significant differences among the African nightshade species when the data’s dimension was reduced using RF variable importance and SIMPER, as also supported by NMDS plots that showed S. scabrum being separated from S. villosum and S. sarrachoides based on the reduced data variables. The novelty of our work is on the merits of using data reduction techniques to successfully reveal differences in groups which could have otherwise not been the case if the analysis were performed on the entire original data matrix characterized by small samples. The R code used in the analysis has been shared herein for interested researchers to customise it for their own data of similar nature.
文摘Survival analysis is a fundamental tool in medical science for time-to-event data. However, its application to colony organisms like bees poses challenges due to their social nature. Traditional survival models may not accurately capture the interdependence among individuals within a colony. Frailty models, accounting for shared risks within groups, offer a promising alternative. This study evaluates the performance of semi-parametric shared frailty models (gamma, inverse normal, and positive stable-in comparison to the traditional Cox model using bees’ survival data). We examined the effect of misspecification of the frailty distribution on regression and heterogeneity parameters using simulation and concluded that the heterogeneity parameter was more sensitive to misspecification of the frailty distribution and choice of initial parameters (cluster size and true heterogeneity parameter) compared to the regression parameter. From the data, parameter estimates for covariates were close for the four models but slightly higher for the Cox model. The shared gamma frailty model provided a better fit to the data in comparison with the other models. Therefore, when focusing on regression parameters, the gamma frailty model is recommended. This research underscores the importance of tailored survival methodologies for accurately analyzing time-to-event data in social organisms.
文摘The efficacy of aqueous and emulsifiable formulations of the fungus Metarhizium anisopliae isolate ICIPE78 was evaluated on the population density of Tetranychus urticae infesting common bean plants under screenhouse and field conditions. Synthetic acaricide abamectin was included as a check. Bean plants were artificially infested with T. urticae and allowed to multiply. Three treatments were applied in the screenhouse and 1 treatment in field trials. Mite density was recorded 2 d before spraying and weekly postspraying. The number of pods per plant, number of seeds per pod, and the dry weight of seeds per plant were recorded only in the screenhouse trials. In both screenhouse and field trials, fungal formulations applied at the concentration of 108 conidia/mL and the aearicide reduced the population density of mites as compared to the controls. There were signif- icant differences in T. urticae population densities between the treatments at the various post-spraying sampling dates. In the screenhouse, the mite densities were near zero from 3-week postspraying in the treated leaves. At 4-week postspraying, there were no more leaves in the untreated control （T1） and in the control water ＋ Silwet-L77 （T2）. Fungal formulations were as effective as abamectin in reducing mite densities in both screenhouse and field experiments. There were significant differences in the production parameters during the 2 screenhouse trials, with fungal and abamectin treatments generally having the highest yield. Results of this study underline the potential of the M. anisopliae isolate ICIPE78 as an alternative to acaricides for T. urticae management.
文摘Tomato (Lycopersicon esculentum) is one of the important vegetables in supplying vitamins, minerals and fiber to human diets worldwide. Its successful production in the tropics is, however, constrained by environmental variations especially under open field conditions. Two trials were conducted at the Horticulture Research and Teaching Field, Egerton University, Kenya to evaluate the effects of agricultural nets (agronets) herein called eco-friendly nets (EFNs) and floating row covers (FRCs) on microclimate modification, yield, and quality of tomato. A randomized complete block design with five replications was used. Tomato plants were grown under fine mesh EFN (0.4-mm pore diameter) cover, large mesh EFN (0.9-mm pore diameter) cover or FRC. The EFN and FRC were maintained either permanently closed or opened thrice a week from 9 am to 3 pm. Two open control treatments were used: unsprayed (untreated control) or sprayed with chemicals (treated control). The use of EFN or FRC modified the microclimate with higher temperatures, lower diurnal temperature ranges, and higher volumetric water content recorded compared with the controls. On the other hand, light quantity and photosynthetic active radiation were reduced by the use of EFN and FRC compared with the controls. The use of FRC and EFN resulted in more fruit and higher percent in marketable yield compared with open field production. Fruit quality at harvest was also significantly improved by the use of EFN and FRC. Fruits with higher total soluble solids (TSS), lower titratable acidity (TA), and higher sugar acid ratio were obtained in EFN and FRC treatments compared with the controls. Fruits harvested from EFN and FRC were also firmer compared with control fruits. These findings demonstrate the potential of EFN and FRC in modifying microclimate conditions and improving yields and quality of tomato under tropical field conditions.
文摘Pollinators use multiple cues whilst foraging in eluding direct cues from flowers and in direct cues from other pollinators. The use of indirect social cues is common in social in sects, such as honeybees and bumblebees, where a social environment facilitates the ability to use such cues. Bumblebees use cues to forage on flowers according to previous foraging experiences. Flowers are an essential food source for pollinators but also pose a high risk of parasite infection through the shared use of flowers leading to parasite spillover. Nevertheless, bumblebees have evolved behavioral defense mechanisms to limit parasite infection by avoiding contaminated flowers. Mechanisms underlying the avoidance of contaminated flowers by bumblebees are poorly understood. Bumblebees were recorded having the choice to forage on non-contaminated flowers and flowers contaminated by a trypan osome gut parasite, Crithidia bombi. The use of different treatments with presence or absence of con specifics on both con taminated and non-contami nated flowers allowed to investigate the role of social visual cues on their pathogen avoidance behavior. Bumblebees are expected to use social visual cues to avoid contaminated flowers. Our study reveals that the presence of a con specific on flowers either con taminated or not does not help bumblebee foragers avoiding contaminated flowers. Nevertheless, bumblebees whereas gaining experie nee tend to avoid their con specific when placed on contami nated flower and copy it whe n on the non-contami nated flower. Our experime nt suggests a detrime ntal impact of floral see nt on disease avoidanee behavior.
文摘Dose-response studies in arthropod research usually involve observing and collecting successive information at different times on the same group of insects exposed to different concentrations of stimulus. When the same measure is collected repeatedly over time, the data become correlated and Probit Analysis technique which is the standard method in analyzing bioassay experiments data cannot be used. Lethal time is estimated when the speed of kill is of interest since mortality varies over time. We evaluate a complementary approach, repeated measures logistic regression using Generalized Estimating Equations (GEE), for lethal time determination in mosquito dose response. Mortality data from anopheles larva exposed to 3 botanical extracts (B,C,E) at 4 concentration levels: 500 mg/ml, 250 mg/ml, 50 mg/ml and 12.5 mg/ml were used. The result shows the estimated LT50 values with concentration 500 mg/ml being the most virulent chemical for extract B (LT50 = 10.3 hrs), C (LT50 = 7.2 hrs) and E (LT50 = 10.3 hrs). The least virulent chemical was concentration 12.5 mg/ml for extract B (LT50 = 52.1 hrs), C (LT50 = 70.7 hrs) and E (LT50 = 55.0 hrs). We conclude that repeated measures of logistic regression via GEE can be used as a tool to estimate LT50 more effectively in repeated measures of arthropod data.
文摘Lepidopteran stem borers are the most damaging pests of maize in Sub-Saharan Africa. Despite the growing importance of maize in the forest zone of Democratic Republic of Congo, no data is available regarding stem borer pest species present and their relative importance. It is thus important to gather information likely to guide future research in this area. This study was undertaken to catalogue stem borer pest species identity and assess their relative infestation levels on maize. Surveys were carried out in wild and cultivated habitats in Kisangani. Five species were collected on maize, i.e., Sesamia calamistis Hampson （1910）, Eldana saccharina Walker （1865）, Busseola fusca Fuller （1901）, Chilo sp. Strand （1913）, and Mussidia nigrivenella Ragonot （1888）. In the wild habitats, Poenoma serrata Hampson, B. fusca and S. calamistis were collected on Pennisetum purpureum whereas Chilo sp. was collected on Panicum maximum. Our results suggest that P. maximum might affect the population dynamics of Chilo sp. whereas P. purpureum is expected not to influence the population dynamics of other stem borers owing to its scarcity in the interior of the forest.
文摘<b><span style="font-family:Verdana;">Background:</span></b><i><span style="font-family:Verdana;"> Plasmodium falciparum</span></i><span style="font-family:;" "=""><span style="font-family:Verdana;"> (</span><i><span style="font-family:Verdana;">Pf</span></i><span style="font-family:Verdana;">) resistance to antimalarial drugs is a major impediment to malaria control. The </span><i><span style="font-family:Verdana;">Pf</span></i><span style="font-family:Verdana;">.</span><i><span style="font-family:Verdana;">Kelch 13</span></i><span style="font-family:Verdana;"> (</span><i><span style="font-family:Verdana;">PfK13</span></i><span style="font-family:Verdana;">) gene has been largely reported to be associated with artemisinin resistance. However, recent studies have shown artemisinin resistance without </span><i><span style="font-family:Verdana;">Kech13 </span></i><span style="font-family:Verdana;">mutations suggesting the implication of others genes in artemisinin resistance. In this current study, we focused on mutations in </span><i><span style="font-family:Verdana;">Pf.</span></i><span style="font-family:Verdana;">actin-binding protein coronin, </span><i><span style="font-family:Verdana;">Pf.</span></i><span style="font-family:Verdana;">c</span><span><span style="font-family:Verdana;">ysteine</span><i> </i><span style="font-family:Verdana;">desulfurase and </span><i><span style="font-family:Verdana;">Pf</span></i><span style="font-family:Verdana;">.plasmepsin 2 gene, three putative candidates recently were reported to be</span><span style="color:red;"> </span><span style="font-family:Verdana;">involved in artemisinin, lumefantrine and piperaquine resistance respectively. </span><b><span style="font-family:Verdana;">Method: </span></b><span style="font-family:Verdana;">Archived blood samples previously collected from asymptomatic school children from December 2016 to October 2018 were used in this study. Genomic DNA was extracted using ISOL</span></span><span style="font-family:Verdana;">ATE II Genomic DNA kit. A
文摘The report sets out to summarize the past and current situation regarding the practice of biologicalcontrol inrelationtothe use and exchange of genetic resources relevant for BCAs.It considers the twomain categories of biological control:classical and augmentative.Allowing access to BCAs for use inanother country imposes no risk of liability to the source country.Local scientific knowledge abouthabitats,fauna andflora,can be
文摘The development of hosts that are resistant and evaluation of botanical extracts to H. armigera Hübner (Lepidoptera: Noctuidae) is crucial for sustainable management, yet very limited in Ethiopia. Therefore, this study was done to identify alternative methods to insecticide control through host consumption study and botanical extracts. The performance of third-fifth larval stages of H. armigera on three host plant varieties including chickpea, tomato and faba bean and botanical extracts against the third larval instars and oviposition deterrence was studied under laboratory condition (22°C ± 2°C, 55% ± 5% RH, 12:12 L: D photoperiod). Significant differences were found in the efficiency of conversion of ingested food (ECI%) (F = 80.06;df = 6, 2;p H. armigera reared on the three host plant varieties of the whole larval instars. The minimum relative consumption rate (RCR) (11.271 ± 0.328) and maximum approximate digestibility (AD) (177.9 ± 1.928) values of the whole larval instars were on Dagaga and Koshari, respectively. The values of relative growth rate (RGR), ECI% and ECD% of the whole larval instars were highest on chickpea varieties and lowest on tomato Koshari. Among chickpea varieties, Habru was relatively resistant to larval instars of H. armigera. Botanical extracts at 50% neem oil (NO), 5% birbira seed extract (BSE) and 5% neem seed extract (NSE) (18.4%) resulted superior in larval mortality however, statistically not different. At both 5% and 2.5% concentration level of botanical extracts the minimum larval mortality was recorded from neem leaf extract (NLE). Maximum numbers of eggs were laid on control treatments and the minimum eggs were on 5% BSE. The deterrent effect of 50% neem oil was stronger (ODI = 17.66%) than that of 5% BSE (ODI = 14%) which is statistically similar value with 5% NSE (ODI = 13%). In conclusion, the result indicated that use of Habru chickpea variety with 50% NO was very effective in controlling both the larvae and deterring the adults of H. armigera from egg lying. These
文摘In recent years, numerous actions for sustainable exploitation of forest resources have been undertaken, but few deal with commercialization of forest insects. Several tree based insect products, like wild silk, can be linked with forest conservation activities to provide livelihood services of different economic scales to forest dependent people. African wild silkmoth, Argema mimosae Boisduval, is one of the forest insects, a moth in the family of Saturniidae producing wild silk, but there is need for definite procedures for extracting silk fibre from its cocoons. This study evaluated physical characteristics of the A. mimosae cocoons and outlined a procedure to extract viable silk fibre for use in silk industry. Cocoons of the A. mimosae were collected from natural forest of Arabuko-Sokoke, Kenya （3020＇ S, 39055＇ E）, and others obtained by semi-captive rearing of the silkmoth larvae. The cocoons of A mimosae were described to be silvery in colour, tough and thick with distinctive perforations on the surface and a prominent valve-like opening with loose filaments at one end. The study recorded 120 min as the optimum boiling time for the cocoons to yield silvery brown silk floss using sodium carbonate （Na2CO3） as the degumming agent. Cocoons boiled in distilled water could not be deflossed into floss, but remained hard and intact, as compared with those of the control, Bombyx mori. This reveals that A. mimosae cocoons can be processed for natural silk fibre production and offer communities adjacent to forests an excellent opportunity to engage in production of natural wild silk.
