Health status of honeybee colonies (Apis mellifera) and disease-associated risk factors in different agroecological zones of Southwest Ethiopia.

A cross-sectional study design was conducted in different agroecological zones of southwest Ethiopia from October 2019 to October 2021. The study aimed to determine the prevalence and associated risk factors for honeybee diseases and pests, as well as the impact of these issues on honeybee colonies and their products. To identify potential risk factors for honeybee disease and pests, a multivariate random effects logistic regression analysis was used. Adult honeybee and brood samples from a total of 384 honeybee colonies were collected and tested using standard laboratory diagnostic methods. The highest prevalence (55.8%) of ants was recorded, followed by wax moths (22.5%) and hive beetles (23.3%). In the current study, the main honeybee diseases observed in the study areas were varroosis (36.5%), bee lice (5.2%), nosemosis (39.6%), amoeba (56%), and chalkbrood (4.5%). However, tracheal mites, sachbrood, and American and European foul brood, were not detected. The agroecological zone (OR = 5.2, 95% CI: 1.75-14.85), type of hive (OR = 2.9, 95% CI: 1.17-17.03), management system (OR = 4.3, 95% CI: 1.23-14.70), and the management of the colony (OR = 3.5, 95% CI: 1.31-9.14) were identified as risk factors for varroosis in these areas. The occurrence of nosemosis in colonies was also influenced by the agroecological zone (OR = 12.2, 95% CI: 3.06-48.54) and colony management (OR = 3.4, 95% CI: 1.59-7.23). The agroecological zone (OR = 10.5, 95% CI: 12.76-22.63) and hive type (OR = 3.0, 95% CI: 1.39-6.36) were the primary risk factors for the occurrence of amoeba in honeybee colonies. However, the occurrence of bee lice (OR = 34.7, 95% CI: 3.96-104.93) and chalkbrood (OR = 4.8, 95% CI: 1.44-13.16) in honeybee colonies was only influenced by the agroecological zone in the study areas. This study demonstrated that losses in honey production in the area are significantly attributed to honeybee disease and pests. Therefore, it is essential to increase public awareness of how honeybee diseases and pests affect honey production and to develop and implement appropriate control measures for these diseases and pests. Furthermore, more studies should be conducted to characterize and isolate other causes of honeybee diseases and pests in various locations.

Epidemiology, factors influencing prevalence and level of varroosis infestation (Varroa destructor) in honeybee (Apis mellifera) colonies in different agroecologies of Southwest Ethiopia.

Little information is available on the epidemiology of varroosis caused by Varroa mite, Varroa destructor infestation in Ethiopia, although it is a devastating honeybee disease that results in significant economic losses in beekeeping. Therefore, between October 2021 and October 2022, a cross-sectional study was carried out in different agroecology zones in Southwest Ethiopia to determine the prevalence and associated risk factors for varroosis, as well as the effects of this disease on honeybee colonies and honey production. A multivariate logistic regression analysis was performed to identify possible risk factors for the prevalence of V. destructor. A total of 384 adult honeybee and worker or drone brood samples were collected from honeybee colonies and examined using standard diagnostic techniques in the laboratory. The result shows that the prevalence of V. destructor was found to be 39.3% (95% CI 34.44-44.21) and 43.2% (38.27-48.18) in adult honeybees and brood, respectively. The major risk factors for the prevalence of V. destructor in the study areas included agroecology (OR = 5.2, 95% CI 1.75-14.85), type of hive (OR = 2.9, 95% CI 1.17-17.03), management system (OR = 4.3, 95% CI 1.23-14.70), and colony management (OR = 3.5, 95% CI 1.31-9.14). The lower level of colony infestation in adult bees and brood was measured as 1.97 ± 0.14 and 3.19 ± 0.25, respectively. Season, colony status, colony management, and agroecology were among the determinant factors of the level of varroa mite infestation in adult bees and brood. The results of the study demonstrated that honey production losses are largely attributable to V. destructor infestation. Therefore, it is critical to inform the community about the effects of V. destructor on honey production and develop and implement effective management strategies for this disease. In addition, further research should be done to identify and isolate additional factors that contribute to varroosis in honeybees in different regions.

Melissopalynological analysis and floral spectra of Apis mellifera scutellata Lepeletier bees in different agroecologies of southwest Ethiopia.

The availability of bee forage limits honeybee productivity and is very important for beekeepers. Therefore, the current study aimed to identify the major botanical resources of honeybee, A. mellifera scutellata, in Southwest Ethiopia. Between October 2019 and October 2020, 69 group discussions (8-12 beekeepers), field observations, and pollen analysis were used to collect data. A total of 72 honey samples were collected from five districts at different seasons for pollen analysis. Most of the honey samples tested (93.06%) were multifloral, while 6.94% were monofloral. Melissopalynological analysis indicated that Eucalyptus camaldulensis (52.02%) was the predominant pollen type and is considered monofloral honey. Terminalia spp. (25.96%), Guizotia spp. (17.80%), and Bidens spp. (17.61%) were secondary pollen types and classified as multifloral honey. Terminalia spp., Guizotia spp., Vernonia spp., Bidens ssp., Plantago spp., and E. camaldulensis were pollen types recorded in honey samples in all agroecologies. Beekeepers ranked Schefflera abyssinica, Vernonia amygdalina, and Cordia africana as the first source of pollen and nectar for honeybees in highland, midland, and lowland, respectively. Additionally, V. amygdalina, Coffea arabica, Croton macrostachyus, and C. africana were commonly observed bee flora in all agroecologies. Honey bee management, such as bee forage shortages, the occurrence of brood and swarming, varied significantly (P < 0.05) among different agroecologies. In the present study, 53 honeybee plants were identified as pollen and nectar sources for honeybees. Various herbs (41.50%), trees (30.20%), and shrubs (28.30%) played a major role in honey production. Thus, beekeeping should be integrated with vegetation conservation for livelihood improvement and food security. Furthermore, existing bee flora should be cultivated in areas to increase the harvesting of honeybee products and improve the apiculture industry.

Association of traits promoting resistance to the adzuki bean beetle, Callosobruchus chinensis (L.) (Coleoptera: Bruchidae) in pea genotypes grown at various soil fertility levels.

Adzuki bean beetle, Callosobruchus chinensis (L.) (Coleoptera: Bruchidae), is one of the most important pests of pea (Pisum sativum L.) crops in Ethiopia. The study focused on the association of resistance potential in the no-choice test of pea genotypes managed at different fertility levels and trait contributions. Based on the significance of fertility levels, genotypes were grouped into four, six, and five clusters, viz. Under neither rhizobium and phosphorus, rhizobium alone and rhizobium and phosphorus, respectively. Regardless of fertility levels, the inter-cluster distance (D2) values of the two potential clusters were highly significant (P < 0.01). At all fertility levels, the average performance of genotypes in each cluster for individual traits to infestation varied significantly. Genotype distribution patterns tended to group together into a small number of clusters. Eighty genotypes of the pea (Pisum sativum L. subsp. sativum and Pisum sativum L. subsp. abyssinicum A. Braun) were systematically managed under three fertility levels, and the first four principal components accounted for 94%, 92.3%, and 94.2% of the total variation. The primary trait that determines the resistance potential of pea genotypes is the trait susceptibility index (SI), which exhibits highly significant and adverse associations with critical traits such as the date of adult emergency and the percentage of seed coat, while exhibiting highly significant and favorable associations with the remaining traits at all fertility levels. The remaining characteristics showed highly significant positive or negative correlations within and particularly with the characteristics that determine resistance. Therefore, the cultivar "Adi" from "Pisum sativum L. subsp. sativum" had higher susceptibility compared to other genotypes, while the small-seeded pea genotypes "Pisum sativum L. subsp. abyssinicum A. Braun"; fpcoll-1/07, fpcoll-2/07, fpcoll-21/07, and fpcoll-43/07 were moderately resistant.

Organic soil fertility management practices for the management of fall armyworm, Spodoptera frugiperda (J.E. Smith), in maize.

The fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), is a polyphagous pest native to the Americas. It attacks several crops but in particular causes significant damage to maize, which is a staple crop in Africa. Organic soil amendments have an impact on the physical, chemical, and biological properties of soil, which enhance plant resistance to or tolerance of insect pests and also promote a diverse population of natural enemies of the pest. However, the practices followed for the management of crop residue and animal manure affect their use as organic soil amendments. A field experiment was conducted to evaluate the effect of maize residue and cattle manure incorporation into soil on FAW in the Mana and Omo Nada districts of the Jimma zone, southwest Ethiopia, during the 2018/19 cropping season. Treatment involved three factors: five different levels of maize residue retention (0%, 25%, 50%, 75%, and 100%), different cattle manure storage systems (control, open, steel roof, and grass roof), and two different districts (Mana and Omo Nada). These variables were organized in a randomized complete block design and replicated three times. The infestation and damage ratings were collected from 30 days after planting at 20-day intervals. The results indicated that maize plots with retained crop residue had a significant reduction in FAW infestation compared with plots without maize residue (control) in both study districts. Furthermore, manure-fertilized plants had a lower percentage of FAW infestation when compared with maize plots without cattle manure in both study districts. The lowest severity of FAW infestation was recorded in a plot with 100% of residue incorporated and treated with cattle manure stored under a grass roof in the Mana district. Therefore, conventional tillage with 100% maize residue incorporation and the application of cattle manure stored under a grass roof showed the best result for reducing FAW infestation in maize. However, further studies are important to determine the effect of treatments over seasons and locations on FAW infestation and maize yields.

Climate variability and aridity modulate the role of leaf shelters for arthropods: A global experiment.

Current climate change is disrupting biotic interactions and eroding biodiversity worldwide. However, species sensitive to aridity, high temperatures, and climate variability might find shelter in microclimatic refuges, such as leaf rolls built by arthropods. To explore how the importance of leaf shelters for terrestrial arthropods changes with latitude, elevation, and climate, we conducted a distributed experiment comparing arthropods in leaf rolls versus control leaves across 52 sites along an 11,790 km latitudinal gradient. We then probed the impact of short- versus long-term climatic impacts on roll use, by comparing the relative impact of conditions during the experiment versus average, baseline conditions at the site. Leaf shelters supported larger organisms and higher arthropod biomass and species diversity than non-rolled control leaves. However, the magnitude of the leaf rolls' effect differed between long- and short-term climate conditions, metrics (species richness, biomass, and body size), and trophic groups (predators vs. herbivores). The effect of leaf rolls on predator richness was influenced only by baseline climate, increasing in magnitude in regions experiencing increased long-term aridity, regardless of latitude, elevation, and weather during the experiment. This suggests that shelter use by predators may be innate, and thus, driven by natural selection. In contrast, the effect of leaf rolls on predator biomass and predator body size decreased with increasing temperature, and increased with increasing precipitation, respectively, during the experiment. The magnitude of shelter usage by herbivores increased with the abundance of predators and decreased with increasing temperature during the experiment. Taken together, these results highlight that leaf roll use may have both proximal and ultimate causes. Projected increases in climate variability and aridity are, therefore, likely to increase the importance of biotic refugia in mitigating the effects of climate change on species persistence.

Subtle structures with not-so-subtle functions: A data set of arthropod constructs and their host plants.

The construction of shelters on plants by arthropods might influence other organisms via changes in colonization, community richness, species composition, and functionality. Arthropods, including beetles, caterpillars, sawflies, spiders, and wasps often interact with host plants via the construction of shelters, building a variety of structures such as leaf ties, tents, rolls, and bags; leaf and stem galls, and hollowed out stems. Such constructs might have both an adaptive value in terms of protection (i.e., serve as shelters) but may also exert a strong influence on terrestrial community diversity in the engineered and neighboring hosts via colonization by secondary occupants. Although different traits of the host plant (e.g., physical, chemical, and architectural features) may affect the potential for ecosystem engineering by insects, such effects have been, to a certain degree, overlooked. Further analyses of how plant traits affect the occurrence of shelters may therefore enrich our understanding of the organizing principles of plant-based communities. This data set includes more than 1000 unique records of ecosystem engineering by arthropods, in the form of structures built on plants. All records have been published in the literature, and span both natural structures (91% of the records) and structures artificially created by researchers (9% of the records). The data were gathered between 1932 and 2021, across more than 50 countries and several ecosystems, ranging from polar to tropical zones. In addition to data on host plants and engineers, we aggregated data on the type of constructs and the identity of inquilines using these structures. This data set highlights the importance of these subtle structures for the organization of terrestrial arthropod communities, enabling hypotheses testing in ecological studies addressing ecosystem engineering and facilitation mediated by constructs. There are no copyright restrictions and please cite this paper when using the data in publications.

Multi-scale mosaics in top-down pest control by ants from natural coffee forests to plantations.

While top-down control plays an important role in shaping both natural and agricultural food webs, we lack insights into how top-down control effects vary across spatial scales. We used a multi-scale survey of top-down control of coffee pests and diseases by arboreal ants to examine if colony location creates a small-scale mosaic in top-down control around trees and if the strength of that control varies between sites at the landscape scale. We investigated pest and disease levels on coffee shrubs at different distances from shade trees with and without a Crematogaster spp. ant colony in 59 sites along a coffee management intensity gradient in southwestern Ethiopia. Within sites, ants significantly suppressed herbivory and coffee leaf rust at distances less than 10 m from nesting trees. Top-down control varied between sites, with stronger top-down control of free-feeding herbivory near ant colonies at sites with lower management intensity and stronger top-down control of a skeletonizer at sites with higher canopy cover. We conclude that the strength of top-down control by ants is highly heterogeneous across spatial scales, as a consequence of the biology of the predator at the small scale and herbivore density or changes in herbivore-ant interactions at the landscape scale.

Natural insecticides for the control of urticating ant, Tetramorium aculeatum Mayr (Hymenoptera: Formicidae) in a coffee plantation of Southwestern Ethiopia.

Coffee, Coffea arabica L. is a vital crop in Ethiopia's social, cultural, and national economy. Despite its dominant role in the country, the crop is challenged by various insect pests, which reduce coffee yield and quality. The urticating ant or biting ant, Tetramorium aculeatum Mayr (Hymenoptera: Formicidae), is an important pest in coffee that affects farming activities in Southwestern Ethiopia. The objective of this study was to evaluate the efficacy of some natural insecticides for the control of biting ants. Nine insecticide treatments were evaluated both under ex-situ and in-situ conditions in CRD and RCBD designs, respectively. Under the ex-situ evaluation, all the insecticide treatments caused significantly higher mortality of biting ants and caused complete mortality within 24 h. Under field conditions, the insecticides showed significant variations in the percent of evacuated nests, and the number of newly constructed nests. In both efficacy tests of ex-situ and in-situ experiments, the mortality of biting ants and percent of evacuated nests in the coffee trees treated with oxymatrine and nimbicidine were found to be comparable and effective as the deltamethrin 2.5% EC. All the insecticide treatments significantly reduced the number of newly constructed nests compared to the control plot. On the other hand, deltamethrin 2.5% EC significantly decreased newly constructed nests after 30 days of application compared to the other insecticide treatments. Generally, the natural insecticides effectively minimized the biting ant infestation, but further studies are essential on the frequency of spray to use them for sustainable management approaches of biting ant in the coffee plantation.

Fall Armyworm, Spodoptera frugiperda Infestations in East Africa: Assessment of Damage and Parasitism.

The fall armyworm (FAW), Spodoptera frugiperda, threatens maize production in Africa. A survey was conducted to determine the distribution of FAW and its natural enemies and damage severity in Ethiopia, Kenya and Tanzania in 2017 and 2018. A total of 287 smallholder maize farms (holding smaller than 2 hectares of land) were randomly selected and surveyed. FAW is widely distributed in the three countries and the percent of infested maize fields ranged from 33% to 100% in Ethiopia, 93% to 100% in Tanzania and 100% in Kenya in 2017, whereas they ranged from 80% to 100% and 82.2% to 100% in Ethiopia and Kenya, respectively, in 2018. The percent of FAW infestation of plants in the surveyed fields ranged from 5% to 100%. In 2017, the leaf damage score of the average of the fields ranged from 1.8 to 7 (9 = highest level of damage), while 2018, it ranged from 1.9 to 6.8. In 2017, five different species of parasitoids were recovered from FAW eggs and larvae. Cotesia icipe (Hymenoptera: Braconidae) was the main parasitoid recorded in Ethiopia, with a percent parasitism rate of 37.6%. Chelonus curvimaculatus Cameron (Hymenoptera: Braconidae) was the only egg-larval parasitoid recorded in Kenya and had a 4.8% parasitism rate. In 2018, six species of egg and larval parasitoids were recovered with C. icipe being the dominant larval parasitoid, with percentage parasitism ranging from 16% to 42% in the three surveyed countries. In Kenya, Telenomus remus (Hymenoptera: Scelionidae) was the dominant egg parasitoid, causing up to 69.3% egg parasitism as compared to only 4% by C. curvimaculatus. Although FAW has rapidly spread throughout these three countries, we were encouraged to see a reasonable level of biological control in place. Augmentative biological control can be implemented to suppress FAW in East Africa.

The Efficacy of Selected Synthetic Insecticides and Botanicals against Fall Armyworm, Spodoptera frugiperda, in Maize.

Fall armyworm (FAW) was reported for the first time in Africa in 2016. FAW is widely distributed in Ethiopia, causing significant damage to maize. Nine synthetic insecticides belonging to different chemical groups and 11 pesticidal plants (botanicals) were tested for their efficacy against FAW under laboratory, greenhouse, and field conditions. In the laboratory, Radiant, Tracer, Karate, and Ampligo caused over 90% larval mortality 72 h after application. Malathion had moderate activity, causing 51.7% mortality 72 h after application, while Carbaryl was less effective, causing 28% mortality 72 h after application. In the greenhouse experiment, all synthetic insecticides reduced foliar damage to maize compared to the untreated control. Chemical sprays did not affect plant height, stem thickness, or leaf number. The highest fresh weight (471 g) was obtained from plants treated with Radiant. Among the botanicals tested, Azadirachta indica, Schinnus molle, and Phytolacca dodecandra resulted in the highest percentage larval mortality (>95%) 72 h after application. In the field, non-treated control plants showed extensive leaf injury compared to the synthetic insecticide- and botanical-treated plants. The synthetic insecticides and botanicals that showed high efficacy against FAW larvae can be used as components for integrated pest management (IPM) plans for FAW under smallholder farmer conditions in Ethiopia and elsewhere in Africa.

Enhancing Neoplasm Expression in Field Pea (Pisum sativum) via Intercropping and Its Significance to Pea Weevil (Bruchus pisorum) Management.

Neoplasm formation, a non-meristematic tissue growth on young field pea (Pisum sativum L.) pods is triggered in the absence of UV light and/or in response to oviposition by pea weevil (Bruchus pisorum L.). This trait is expressed in some genotypes [neoplastic (Np) genotypes] of P. sativum and has the capacity to obstruct pea weevil larval entry into developing seeds. In the present study, 26% of the tested accessions depicted the trait when grown under greenhouse conditions. However, UV light inhibits full expression of this trait and subsequently it is inconspicuous at the field level. In order to investigate UV light impact on the expression of neoplasm, particular Np genotypes were subjected to UV lamp light exposure in the greenhouse and sunlight at the field level. Under these different growing conditions, the highest mean percentage of Np pods was in the control chamber in the greenhouse (36%) whereas in single and double UV lamp chambers, the percentage dropped to 10 and 15%, respectively. Furthermore, when the same Np genotypes were grown in the field, the percentage of Np pods dropped significantly (7%). In order to enhance Np expression at the field level, intercropping of Np genotypes with sorghum was investigated. As result, the percentage of Np pods was threefold in intercropped Np genotypes as compared to those without intercropping. Therefore, intercropping Np genotypes with other crops such as sorghum and maize can facilitate neoplasm formation, which in turn can minimize the success rate of pea weevil larvae entry into developing seeds. Greenhouse artificial infestation experiments showed that pea weevil damage in Np genotypes is lower in comparison to wild type genotypes. Therefore, promoting Np formation under field conditions via intercropping can serve as part of an integrated pea weevil management strategy especially for small scale farming systems.

Oviposition Preference of Pea Weevil, Bruchus pisorum L. Among Host and Non-host Plants and its Implication for Pest Management.

The pea weevil, Bruchus pisorum L. is a major insect pest of field pea, Pisum sativum L. worldwide and current control practices mainly depend on the use of chemical insecticides that can cause adverse effects on environment and human health. Insecticides are also unaffordable by many small-scale farmers in developing countries, which highlights the need for investigating plant resistance traits and to develop alternative pest management strategies. The aim of this study was to determine oviposition preference of pea weevil among P. sativum genotypes with different level of resistance (Adet, 32410-1 and 235899-1) and the non-host leguminous plants wild pea (Pisum fulvum Sibth. et Sm.) and grass pea (Lathyrus sativus L.), in no-choice and dual-choice tests. Pod thickness and micromorphological traits of the pods were also examined. In the no-choice tests significantly more eggs were laid on the susceptible genotype Adet than on the other genotypes. Very few eggs were laid on P. fulvum and L. sativus. In the dual-choice experiments Adet was preferred by the females for oviposition. Furthermore, combinations of Adet with either 235899-1 or non-host plants significantly reduced the total number of eggs laid by the weevil in the dual-choice tests. Female pea weevils were also found to discriminate between host and non-host plants during oviposition. The neoplasm (Np) formation on 235899-1 pods was negatively correlated with oviposition by pea weevil. Pod wall thickness and trichomes might have influenced oviposition preference of the weevils. These results on oviposition behavior of the weevils can be used in developing alternative pest management strategies such as trap cropping using highly attractive genotype and intercropping with the non-host plants.

Semiochemicals used in host location by the coffee berry borer, Hypothenemus hampei.

The coffee berry borer, Hypothenemus hampei is a serious pest in many coffee growing countries. Electrophysiological and behavioral responses of H. hampei to volatiles of different phenological stages of coffee, Coffea arabica, fruits were studied in order to identify volatile semiochemicals used in host location. Volatiles were collected from different phenological stages of C. arabica fruit by air entrainment. Electrophysiological recordings were made from insect antennae. Behavioral assays were carried out using a Perspex four-arm olfactometer. Insects spent significantly more time in the region of the olfactometer where ripe and dry fruit volatiles were present compared to control regions. Coupled gas chromatography--electroantennography revealed the presence of six electrophysiologically active compounds in C. arabica volatiles. These were identified by using GC and GC-MS as methylcyclohexane, ethylbenzene, nonane, 1-octen-3-ol, (R)-limonene, and (R)-3-ethyl-4-methylpentanol. In the olfactometer bioassay, H. hampei showed a significant response to 3-ethyl-4-methylpentanol, methylcyclohexane, nonane, ethylbenzene, and a synthetic blend of these four compounds. Attraction to the synthetic blend was comparable to that for the natural sample. The significance of the study is discussed in terms of semiochemical based pest management methods of the coffee berry borer.