Antestia Bug Research Articles

Investigating sensory-classified roasted arabica coffee with GC × GC-TOFMS and chemometrics to understand potato taste defect

The presence of flavor defects in coffee beans can negatively impact quality, the consumer experience, and commercial trade. Potato taste defect (PTD), a flavor defect specific to East African coffee, is often characterized by a musty, vegetable-like aroma. While previous work has correlated PTD with the presence of 2-isopropyl-3-methoxypyrazine (IPMP), additional changes in the volatile profile of these beans can further amplify the distinct odor of this defect. The aim of this work was to develop a volatile fingerprint of PTD in roasted arabica coffee using headspace solid-phase microextraction coupled to comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (HS-SPME-GC × GC-TOFMS) and chemometrics. Examination of the HS-SPME-GC × GC-TOFMS data with tile-based Fisher ratio (F-ratio) analysis discovered 359 analytes that differentiated clean coffee samples from those impacted by severe PTD (p-value < 0.01). It was determined that 327 of the identified analytes were more prevalent in the clean coffee samples while 32 analytes, including IPMP, exhibited higher signals in the impacted coffee samples. Principal components analysis (PCA) of the F-ratio results demonstrated that the coffee samples clustered based on the presence of PTD. Partial least squares (PLS) regression modeling further demonstrated that the compounds discovered by F-ratio analysis were correlated with PTD by accurately predicting the concentration of IPMP in the samples. Investigation of the compounds highly weighted in both the PCA and PLS loadings suggest that the presence of microorganisms on coffee beans after antestia bug damage could be a potential pathway for PTD. This damage results in an overall decrease of analytes that are known to have positive sensory contributions to coffee aroma. Collectively, the volatile fingerprint shown herein illustrates that PTD alters the biochemical process in coffee beans.

The insect pests of coffee and their management practices in the main coffee growing region in Kenya

Coffee farming in Kenya is a major source of income for over 800,000 farmers. Globally, the Kenyan coffee is renowned for its high quality. Most of the Kenyan coffee is produced in the Mt. Kenya region. Its production faces many challenges that include infestation by a complex of insect pests. A field survey covering eight (8) main coffee-growing counties and 485 households in the Mt. Kenya region was conducted in May 2022. The survey aimed to establish the key insect pests in the region, and their distribution and management practices applied by the farmers. The survey established eight (8) insect pests as of major importance in the region. These included the Coffee Berry Borer (Hypothenemus hampei), Thrips (Diarthrothrips coffeae), Leaf miners (Leucoptera spp), Yellow Headed Borer (Dirphya nigricornis), White Borer (Anthores leuconotus), Green scales (Coccus alpinus), Kenya Meallybugs (Planococcus kenyae) and Antestia bugs (Antestiopsis spp). Their occurrence ranged from 5 to 66%. The C. alpinus (66%) occurred in all the surveyed counties, Agro-Ecological Zones (AEZs) and coffee farms’ households. The D. nigricornis (57%) was the second most common insect pest. The C. alpinus, D. nigricornis, Leucoptera spp and H. hampei dominated the “Lower” coffee zone and were less dominant in Upper Midland 1(UM 1). Farmers used insecticides, plant extracts, and physical, mechanical, cultural, and field sanitation approaches to control the pests. Insecticides at 79% was the most widespread practice used by coffee farmers. This study and its findings are key to Agricultural extension services in providing focused technical advisory services to coffee farmers based on specific insect pests per the Agro-Ecological Zones from the Mt Kenya region. Keywords: Agro-ecological zones, insect pests, infestation, management practices.

Status and Importance of Major Coffee Insect Pests in Major Coffee Growing Areas of Southern Ethiopia

In Ethiopia, coffee is known as the backbone of economy although the productivity was very low due to different factors. Among these, insect pests are one of the major affecting coffee productions in Ethiopia. The present study was conducted to assess the status of major coffee insect pests in major coffee growing areas of Southern Ethiopia. The survey result revealed that the infestation and damage level of insect pests varies among coffee fields, peasant associations and districts. The maximum percent of damaged coffee bean and number of antestia bug per tree was recorded at Wonago, 4.0% and 0.75 respectively. The mean number of bugs and bean damage levels were higher at higher elevations range (1931-2025 m.a.s.l) of Wonago district whereas the lower level was recorded at lower elevations range of (1449-1695 m.a.s.l) of Dilla Zuria district. The percent of infested farms of coffee blotch leaf miner (100%) was recorded in all assessed districts whereas the highest infestation of skeletonizer (90.90%) and serpentine coffee leaf miner (81.81%) at Dilla Zuria district. From the survey result the highest coffee blotch leaf miner infestation level was recorded at Aleta Wondo district (15.13%) while the lowest was at Dilla Zuria (5.32%); the highest infestation of skeletonizer (1.02%) and serpentine (0.60%) at Wonago while the lowest was (0.22%) and (0.10%) at Shebedino district, respectively. Lack of consulting professionals and practicing coffee agronomic recommendations were the knowledge gaps identified among the farmers and hence, adequate training for farmers and extension workers as well as districts’ experts is needed. As future line, further studies should be conducted on the seasonal dynamics and developing integrated insect pest management strategies for major insect pests of coffee.

Functional land cover scale for three insect pests with contrasting dispersal strategies in a fragmented coffee-based landscape in Central Kenya

In the Eastern Africa highlands, the gradual transformation of natural ecosystems to smallholding coffee-based agrosystems has resulted in more fragmented landscapes. Major pests of coffee find appropriate living conditions leading to high infestation rates and the need for smallholder farmers to implement pest control measures. This study aims to understand the influence of landscapes on the ecology of three major coffee pests: the coffee berry borer (CBB), Hypothenemus hampei, and the Antestia bugs Antestiopsis thunbergii (ABT) and A. facetoides (ABF). The study was conducted on a typical smallholder coffee-based landscape in central Kenya. The pest abundance was assessed monthly for two years in a network of 30 coffee plots spread across the coffee agro-ecological subzones (AEsZ), namely upper midland UM1 and UM2, and the transition zones between UM1 and UM2 and between UM2 and UM3, herein referred to as TZ1 and TZ2, respectively. Landscape metrics, viz. patch density, Euclidean nearest neighbour distance, proximity index, contagion index, interspersion and juxtaposition index were derived from a spatially explicit land cover map, based on 10 m Sentinel 2 data for nine buffer zones of radius ranging from 50 m to 1000 m around each sampled plot. Redundancy analysis (RDA) was used to establish the relationships between the observed pest abundances and landscape metrics, elevation, and AEsZ. Landscape indicators achieved the highest correlation with the pest abundances within a 300 m radius (Adjusted R2 > 0.5). Whereas beyond 300 m landscape scale, the predictor variables resulted in weak relationships (Adjusted R2 < 0.5) between the pests abundance and landscape metrics. We noted a strong influence of elevation and adjacency to cropland on Antestia bug populations. Specifically, ABF populations were negatively correlated with low elevation, whereas ABT’s were positively correlated with high elevation zone. On the other hand, CBB was strongly influenced by contiguous coffee patches, especially in UM1 and UM2. Therefore, we recommend reducing connectivity between coffee patches for the management of CBB, whereas further studies should be conducted to identify secondary hosts of Antestia bugs that should not be adjacent or within coffee stands.

The Efficacy of Entomopathogenic Fungi for Antestia Bugs (&amp;lt;i&amp;gt;Antetiopsis intircata&amp;lt;/i&amp;gt;: Pentatomidea, Hemimptera) Control

Antestia bug (<i>Antestiopsis intricata</i>) is the major coffee insect pest affecting coffee productions in Ethiopia. Therefore, the study was carried out to evaluate entomopathogenic fungi based management options for antestia bug control. The efficacy test of entomopathogenic fungi was done under laboratory condition in Jimma Agricultural Research Center, Entomology and Pathology laboratories. The entomopathogenic fungi isolates were brought from Haramaya University and Ambo Agricultural Research Center. Seven isolates of <i>Beauvaria bassiana</i> (DLCO-12, APPRC-0247, DLCO-90, DLCO-56, DLCO-76, PPRC-44BC, and PPRC-27J) and four isolates of <i>Metarhizium ansopliae</i> (PPRC-51, DLCO23A, DLCO-91 and PPRC-02BC) species were tested for germination. Completely Randomized Design with three replications and probit analysis were used for data analysis by using SAS, GenStat and Microsoft excel. Eight isolates: APPRC 0247, DLCO 90, DLCO 56, DLCO 76, PPRC-44BC, PPRC-27J, PPRC-51 and PPRC-02BC which recorded higher germination were used for pathogenicity test against antestia bugs. All the tested isolates killed antestia bugs but their levels of efficacy differ across exposure time. Among tested isolates, PPRC-44BC and PPRC-27J registered complete mortality against antestia bugs and lower median lethal time, LT₅₀ (9.98 and 10.98 days, respectively). As a result these were taken as promising isolates and used for further isolates rate test. PPRC-44BC and PPRC-27J isolates applied at 1x10⁸ conidia ml^-1 killed all the tested antestia bugs in shorter exposure time. Even though PPRC-44BC and PPRC-27J isolates showed promising results under laboratory conditions, it needs further investigations on its formulation and under field conditions. Isolations of biocontrols from natural coffee growing areas and the effect of biocontrols against natural enemies should be studied.

Application Frequency of &amp;lt;i&amp;gt;Beauvaria bassiana&amp;lt;/i&amp;gt; Isolates Against Antestia Bugs (&amp;lt;i&amp;gt;Antetiopsis intircata&amp;lt;/i&amp;gt;: Pentatomidea, Hemimptera) Management

The production and productivity of coffee is affected by many insect pests and Ethiopian farmers get below 0.636 tons per hectare. Among insect pests Antestia bug is the major coffee insect pest affecting coffee productions. Therefore, the study was carried out to determine the frequency of promised Entomopathogenic fungi isolates against antestia bug. The experiment was done in Jimma Agricultural Research Center, Entomology and Pathology laboratories. Used entomopathogenic fungi isolates were brought from Ambo Agricultural Research Center. Two isolates of Beauvaria bassiana, PPRC-44BC and PPRC-27J isolates applied at 1x10⁸ conidia ml^-1 and three times were used for the experiment. Completely randomized design with three replications and probit analysis were used for data analysis by using SAS software version 9.3. PPRC-44BC and PPRC-27J isolates killed all the tested Antestia bugs in exposure time. The isolates applied three times reduced median lethal time by 42.13 and 38.89%, respectively as compared to with their respective one time application. The correlation result also showed that there was strong negative correlation between application frequency of isolates and median lethal times (LT₅₀ and LT₉₀ were r=-0.811 and r=-0.714, respectively). The study indicated that the more frequently applied isolates the shorter the median lethal time. This showed promising result in the microbials based insect pest management methods and need further investigations under field conditions and the effect of these isolates against natural enemies of the pest.

Population distribution and density of Antestiopsis thunbergii (Hemiptera: Pentatomidae) in the coffee growing regions of Rwanda in relation to climatic variables

Antestia bug, Antestiopsis thunbergii (Gmelin, 1970) (Hemiptera: Pentatomidae) is one of the most damaging pests of coffee (Coffea arabica, L.) worldwide, except in central and south America. A two – year study was conducted to assess the distribution and the density of Antestia bug in the coffee growing regions of Rwanda, and to determine the effects of climatic variables on density of Antestia bug. 205 farms were surveyed in 2016 and 191 farms in 2017. The density and damage of Antestia bug were quantified and climatic variables including temperature, rainfall, wind speed and relative humidity were recorded. Antestia bug was distributed in all coffee growing regions of Rwanda, during both study periods. Over both years, the highest density was recorded in the northern region of the country while the lowest was recorded in the eastern region. The economic damage due to Antestia bug ranged from 0 to 92% and from 0 to 81% in 2016 and 2017, respectively. Stepwise multiple linear regression analysis indicated that temperature and rainfall significantly influenced pest density. However, wind speed was not significantly associated with the density of Antestia bug. Principal component analysis (PCA) indicated three distinct groupings. Coffee regions that received higher, regular rains had a higher population of Antestia bug than where rains were erratic. Similarly, the areas where temperature was consistently high had high densities of Antestia bug. Wind speed was highly and negatively related to principal component one. This study indicated the need to intensify control measures against Antestia bug. Furthermore, the impact of climate change on density and damage of Antestia bug and other coffee pests needs further research.

Options for Managing Antestiopsis thunbergii (Hemiptera: Pentatomidae) and the Relationship of Bug Density to the Occurrence of Potato Taste Defect in Coffee

Potato taste defect is a potato-like smell found in green and roasted coffee beans. Potato taste defect reduces the flavor experience of finished coffee and causes it to be rejected by consumers. The presence of potato taste defect has been associated with insect damage, especially damage from the Antestia bug, Antestiopsis thunbergii (Gremlin) (Hemiptera: Pentatomidae). A 2-yr study was conducted to evaluate the effectiveness of integrated pest management using pruning alone or in combination with several commercially available insecticides to control a field population of Antestia bug and to assess the relationship between these treatments and the occurrence of potato taste defect in coffee using laboratory and field tests. Field trials were conducted in 3 major coffee growing regions of Rwanda: Rubona, Gakenke, and Kirehe. In laboratory bioassays, significant differences were found between insecticides on the percentage mortality of adult bugs. The percent mortality was higher for pyrethroid, Fastac (Alpha-cypermethrin), and pyrethrins (Pyrethrum 5EW, Pyrethrum EWC + Sesame and Agroblaster) than for the neonicotinoid, imidacloprid. Mortality from imidacloprid increased over time, providing a lower mortality than Pyrethrum 5EW and Agroblaster 12 h post-treatment. In the field, the highest mean mortality was achieved with Pyrethrum 5EW, Fastac, and Pyrethrum EWC applied to pruned coffee trees. Additionally, pruning alone registered a statistically higher mean insect mortality than unpruned coffee trees without insecticides application. Multiple logistic regression analysis indicated that potato taste defect was positively associated with the bug density and the extent of damage caused by Antestia bug. The study suggests that pruning combined with insecticide application, especially Fastac, provides better control of Antestia bug and significantly reduces potato taste defect compared to either pruning or insecticide application alone.

Occurrence of potato taste defect in coffee and its relations with management practices in Rwanda

Coffee production is a critical export for Rwanda and a direct income source for many rural farmers. An undesirable raw potato-like smell found in parchment, green and roasted coffee beans and in brewed cups of coffee referred to as “potato taste defect” (PTD) affects coffee across the Africa Great Lakes Region. Two main insect pests of coffee, antestia bug (Antestiopsis thunbergii) and coffee berry borer (Hypothenemus hampei) occur in the same region and may be directly or indirectly responsible for the spread of PTD. The objectives of this study were to determine the distribution of PTD in Rwanda and to evaluate how crop management practices influence the occurrence of this defect in coffee. A stratified random sample of 338 coffee farms was selected and the density of antestia bug and damage to coffee berries attributed to antestia bug or coffee berry borer (CBB) were quantified. Management practices such as pruning, intercropping and insecticides application were recorded. A random sample of three kg of ripe cherries was collected from each farm, hand pulped, fermented for 24 h, washed, dried and tested. Processing did not include sorting by floatation or removal of insect - infested cherries. Potato taste defect was detected in about 5% of the samples. The PTD was distributed throughout the coffee producing regions of Rwanda with the highest incidence in the Central Plateau, Granitic Ridges and Eastern Plateau. Occurrence of PTD was significantly correlated with antestia bug density and damage but not to CBB infestation. Pruning significantly reduced the occurrence of PTD but intercropping did not affect the occurrence of this defect in coffee. This study suggests that PTD could be significantly reduced through proper control of antestia bug, but its elimination would also require understanding its mechanisms of infection.

Prediction of insect pest distribution as influenced by elevation: Combining field observations and temperature-dependent development models for the coffee stink bug, Antestiopsis thunbergii (Gmelin).

The antestia bug, Antestiopsis thunbergii (Gmelin 1790) is a major pest of Arabica coffee in Africa. The bug prefers coffee at the highest elevations, contrary to other major pests. The objectives of this study were to describe the relationship between A. thunbergii populations and elevation, to elucidate this relationship using our knowledge of the pest thermal biology and to predict the pest distribution under climate warming. Antestiopsis thunbergii population density was assessed in 24 coffee farms located along a transect delimited across an elevation gradient in the range 1000–1700 m asl, on Mt. Kilimanjaro, Tanzania. Density was assessed for three different climatic seasons, the cool dry season in June 2014 and 2015, the short rainy season in October 2014 and the warm dry season in January 2015. The pest distribution was predicted over the same transect using three risk indices: the establishment risk index (ERI), the generation index (GI) and the activity index (AI). These indices were computed using simulated life table parameters obtained from temperature-dependent development models and temperature data from 1) field records using data loggers deployed over the transect and 2) predictions for year 2055 extracted from AFRICLIM database. The observed population density was the highest during the cool dry season and increased significantly with increasing elevation. For current temperature, the ERI increased with an increase in elevation and was therefore distributed similarly to observed populations, contrary to the other indices. This result suggests that immature stage susceptibility to extreme temperatures was a key factor of population distribution as impacted by elevation. In the future, distribution of the risk indices globally indicated a decrease of the risk at low elevation and an increase of the risk at the highest elevations. Based on these results, we concluded with recommendations to mitigate the risk of A. thunbergii infestation.

Ripe coffee berry volatiles repel second instar nymphs of Antestia bugs (Heteroptera: Pentatomidae: Antestiopsis thunbergii)

Understanding the roles of volatile organic compounds (VOCs) in insect–plant interactions is a key component towards the development of safe pest management strategies and sustainable agriculture. Kairomones in unripe berries of Coffea arabica mediate host recognition of second instar nymphs of Antestia bugs, Antestiopsis thunbergii Gmelin, and are good candidates for the pest management. In the current study, we investigated the VOCs that contribute to deterring the pest from ripe berries. Behavioral assays showed that headspace volatiles collected from ripe berries were significantly avoided by second instar nymphs. A mixture of the ripe berry volatiles and unripe berries (known preferred diet) was also significantly avoided when tested against blank or unripe berries, thereby confirming that VOCs from ripe berries had altered the host recognition process and had an odor masking effect. Coupled gas chromatography/mass spectrometric (GC/MS) analysis of the headspace volatiles revealed a blend of chemicals of which ten elicited electrophysiological activity in antennae of second instar nymphs. Five of these compounds including; 3-hydroxy-2-butanone, 2-heptanone, 2-isopropyl-3-methoxypyrazine [IPMP], 2-isobutyl-3-methoxypyrazine [IBMP] and (E)-β-caryophyllene were identified as unique to the volatiles of ripe berries and they elicited avoidance behavior in second instar nymphs when tested singly and in a blend. In addition, their blend also inhibited responses of nymphs to a synthetic attractant blend (kairomone). Our results suggest that the blend of the five compounds can be exploited as repellents in the management of A. thunbergii by pushing the pest away from coffee plantations or interfering with the pest–host recognition process through masking of suitable host odors.

Temperature-dependent models of development and survival of an insect pest of African tropical highlands, the coffee antestia bug Antestiopsis thunbergii (Hemiptera: Pentatomidae)

The antestia bug Antestiopsis thunbergii (Hemiptera: Pentatomidae) is a major pest of Arabica coffee in African tropical highlands. It feeds on coffee plant vegetative parts and berries leading to a direct reduction in coffee yield and quality. This study aimed to determine A. thunbergii thermal requirements, and to obtain new information on the pest demography as influenced by temperature. Temperature-dependent models were developed using the Insect Life Cycle Modelling software (ILCYM) through a complete life table study at seven constant temperatures in the range 18–32°C. Non-linear functions were fitted to A. thunbergii development, mortality, fecundity and senescence. Model parameters and demographic variables obtained from the models were given for each temperature and development stage. Life table parameters were estimated for nine constant temperatures, from 18°C to 26°C, using stochastic simulations. The minimum temperature threshold (Tmin) and the thermal constant (k) for the development from egg to adult were estimated from a linear function at 12.1°C and 666.67° days, respectively. The maximum temperature threshold (Tmax) was estimated at 33.9°C from a Logan model. The optimum temperature for immature stages’ survival was estimated to be between 22.4 and 24.7°C. The maximum fecundity was 147.7 eggs female−1 at 21.2°C. Simulated A. thunbergii life table parameters were affected by temperature, and the maximum value of intrinsic rate of increase (rm) was 0.029 at 22°C and 23°C. In general, the life cycle data, models and demographic parameters we obtained were in line with previous reports for antestia bugs or other stink bug species. The relationships between the pest thermal requirements and ecological preferences in highland coffee were discussed. Our results will contribute to risk prediction under climate change for this important coffee pest.

Evaluation of Entomopathogenic Fungi against Coffee Antestia Bug, (Antestiopsis Intricate) Under Laboratory Condition at Jimma

Evaluation of Entomopathogenic Fungi against Coffee Antestia Bug, (Antestiopsis Intricate) Under Laboratory Condition at Jimma

Innovative Strategies for Control of Coffee Insect Pests in Tanzania: A Review

Coffee insect pests are one of the major factors which affect coffee production and quality. globally, coffee insect pests are estimated to cause losses of about 13%. However in Africa, yield losses can be much higher, particularly where Arabica and Robusta coffee are grown for a long time. In Tanzania the major insect pests are white coffee stem borer (Monochamus leuconatus), coffee berry borer (Hypothenemus hampei), Antestia bugs (Antestiopsis spp), leaf miner (Leucoptera spp), green scale (Coccus spp) and mealy bugs (Planococcus kenyae). Minor important pests including yellow headed borer (Dirphya nigricornis), thrips (Diarthrothrips coffeae) and berry moth (Prophants smaragdina) are reported to vary in crop losses caused. For decades industrial chemicals have been used to control the prevailing coffee insect-pests. But uses of industrial chemicals have been reported to have negative implications to the environment, animals and human health. In the recent years worldwide, efforts have been focused to researching on the sustainable control measures for coffee insect pests. For a period of over ten years Tanzania Coffee Research Institute (TaCRI) has been developing ecologically and environmentally sustainable coffee insect-pests control measures which include; use of bio pesticides, traps, parasites, attractants and biological agents. These technologies are progressively adopted by coffee farmers in the country. The potential of these innovative insect pests control measures and their impacts on management of coffee insect pests are discussed in this review paper.

Relating shading levels and distance from natural vegetation with hemipteran pests and predators occurrence on coffee

AbstractThe study was carried out to determine the effect of shading levels and/or distance from the natural alpine vegetation (NAV) on the occurrence of two insect functional groups: hemipteran herbivores and generalist predators in farmers' coffee fields in the Mt. Elgon region of Uganda. Three distance categories from the NAV, that is (i) 0–250 m; (ii) 250–1000 m and (iii) 1000–1500 m, were used to demarcate farms in the first stage of selection, and within each distance category, three levels of shading, that is (i) no shade, (ii) moderate shade and (iii) full shade, were used for final selection of coffee farms for the study. A total of 90 individually owned coffee fields were studied; 30 for each distance category, of which 10 represented each shading level. In two separate rounds, inventories of scale insects (Coccus spp.), antestia bugs (Antestiopsis spp.), root mealybugs (Planococcus spp.) and aphids (Toxoptera aurantii) on coffee plants were made for the hemipteran herbivores, whereas ants (Formicidae) and spiders (Araneae) were recorded for the predatory taxa. The results showed that the interaction between distance from the NAV and shading level consistently influenced the occurrence of the insects in both functional groups. For scale insects, root mealybugs and ants, it was closest to the NAV that shading‐level effects were most discernible and generally limiting. To the contrary, the occurrence of aphids and spiders increased with the increase in the level of shading for plants furthest from the NAV. These results indicate that if inclusion of shade trees is to be a strategy in ecological pest management, the level of shading should be determined basing on the insect taxa as well as other pertinent factors in the landscape.

Potential Impact of Climate Change on Dynamics of Coffee Berry Borer (Hypothenemus hampi Ferrari) in Ethiopia

The aim of this paper is to review the potential effect of climate change on dynamics of coffee berry borer and to generate information for researches concerned on it. Coffee (Coffea arabica L.), which is originated in Ethiopia, is the backbone of the country's economy. It accounts for 70% of the for- eign exchange earning, 10% of the government revenue and employs 25% of the domestic labor force. There are four coffee production systems in Ethiopia such as modern plantation, gardens, semi-forest and forest coffee. Among the major factors limiting increased Coffee production glo- bally are losses due to pests and estimated to be 13% worldwide. Over 47 species of insect pests are recorded on Coffee in Ethiopia. Among which Antestia bug, Antestiopsis intricate, A. facetoids and Coffee blotch miner, Leucopteracaffeinia are the major ones inflicting considerable damage as well as insect pests such as Coffee berry borer, Hypothenemus hampei, Coffee thrips, Diarthroth- ripscoffeae, green scale, Coccusalpinus and Coffee cushion scale, Stictococcusformicarius, are po- tentially important insect pests in Ethiopia. In addition to pest constraints, Africa are expected to be placed under considerable additional stress by climate change. This is of particular importance for crops such as coffee, which serves as the economic foundation for many countries in the trop- ics. The Greater Horn of Africa is among the most vulnerable regions to the impacts of climate va- riability and change. Smallholder coffee farmers are more vulnerable to it, because of various con- straints negatively affecting their livelihoods. Climate-induced stress may render plants more vulnerable to opportunistic herbivores. Before 1984, temperatures in the Ethiopian highland's coffee growing regions were cool enough to keep the coffee berry borer in check. However, rising temperatures have enabled several generations of beetles per coffee season. While surveys in 1967 did not show any evidence of coffee berry borers, those conducted in 2003 found that the beetle was widespread in Southwestern Ethiopia. The rise in temperatures and infestation of cof- fee berry borers may already be affecting Ethiopian coffee crops. From 2002 to 2009, coffee yields plunged by nearly 35 percent. Rising temperatures are threatening the nation's coffee crops by * Corresponding author.

GCMS investigation of volatile compounds in green coffee affected by potato taste defect and the Antestia bug.

Potato taste defect (PTD) is a flavor defect in East African coffee associated with Antestiopsis orbitalis feeding and 3-isopropyl-2-methoxypyrazine (IPMP) in the coffee. To elucidate the manifestation of PTD, surface and interior volatile compounds of PTD and non-PTD green coffees were sampled by headspace solid phase microextraction and analyzed by gas chromatography mass spectrometry. Principal component analysis of the chromatographic data revealed a profile of surface volatiles distinguishing PTD from non-PTD coffees dominated by tridecane, dodecane, and tetradecane. While not detected in surface volatiles, IPMP was found in interior volatiles of PTD coffee. Desiccated antestia bugs were analyzed by GCMS, revealing that the three most prevalent volatiles were tridecane, dodecane, and tetradecane, as was found in the surface profile PTD coffee. Coffee having visible insect damage exhibited both a PTD surface volatile profile and IPMP in interior volatiles, supporting the hypothesis linking antestia bug feeding activity with PTD profile compounds on the surface and IPMP in the interior of the beans.

Bacterial symbionts of a devastating coffee plant pest, the stinkbug Antestiopsis thunbergii (Hemiptera: Pentatomidae).

Stinkbugs of the genus Antestiopsis, so-called antestia bugs or variegated coffee bugs, are notorious pests of coffee plants in Africa. We investigated the symbiotic bacteria associated with Antestiopsis thunbergii, a major coffee plant pest in Rwanda. PCR, cloning, sequencing, and phylogenetic analysis of bacterial genes identified four distinct bacterial lineages associated with A. thunbergii: a gammaproteobacterial gut symbiont and symbionts representing the genera Sodalis, Spiroplasma, and Rickettsia. In situ hybridization showed that the gut symbiont densely occupied the lumen of midgut crypts, whereas the Sodalis symbiont, the Spiroplasma symbiont, and the Rickettsia symbiont sparsely and sporadically infected various cells and tissues. Diagnostic PCR survey of 154 A. thunbergii individuals collected at 8 localities in Rwanda revealed high infection frequencies (100% for the gut symbiont, 51.3% for the Sodalis symbiont, 52.6% for the Spiroplasma symbiont, and 24.0% for the Rickettsia symbiont). These results suggest that the gut symbiont is the primary symbiotic associate of obligate nature for A. thunbergii, whereas the Sodalis symbiont, the Spiroplasma symbiont, and the Rickettsia symbiont are the secondary symbiotic associates of facultative nature. We observed high coinfection frequencies, i.e., 7.8% of individuals with quadruple infection with all the symbionts, 32.5% with triple infections with the gut symbiont and two of the secondary symbionts, and 39.6% with double infections with the gut symbiont and any of the three secondary symbionts, which were statistically not different from the expected coinfection frequencies and probably reflected random associations. The knowledge of symbiotic microbiota in A. thunbergii will provide useful background information for controlling this devastating coffee plant pest.

Incidence and severity of coffee leaf rust and other coffee pests and diseases in Rwanda

Coffee Leaf Rust (CLR) caused by Hemileia vastatrix Berk. and Br. has a worldwide distribution and causes enormous yield losses. A survey was conducted in Rwanda to evaluate incidence and severity of CLR and other coffee pests and diseases and to determine how the crop management contributes to CLR severity. A stratified random sample of 307 coffee farms was visited and the prevalence, incidence and severity were recorded. Results showed that all provinces were affected by CLR with the highest severity in Eastern province where the incidence was up to 100%. High altitudes were associated with low disease severity with a negative correlation of - 0.71. Coffee berry disease (CBD) was a minor disease but with a potential to become an epidemic in the future. Coffee leaf miner, Antestia bugs and Coffee stem borer were recorded but were managed below economic injury levels. All commercial cultivars were susceptible to CLR and most management practices such as mulching, pruning and fertilizer application were associated with lower levels of CLR severity except intercropping which resulted in higher disease intensity. Implications of this survey in relation to CLR management in Rwanda are discussed in this study. Key words: Coffee, diseases, incidence, severity, management, Rwanda.

Efficacy of plant essential oils against two major insect pests of coffee (Coffee berry borer, Hypothenemus hampei, and antestia bug, Antestiopsis intricata) and maize weevil, Sitophilus zeamais

Coffee berry borer, antestia bug and maize weevil are serious pest of coffee and maize, respectively. Bioassays of plant essential oils were conducted with coffee berry borer, antestia bug and the maize weevil. Essential oils of Thymus vulgaris, Aloysia sp., Ruta chalepensis, Chenopodium ambrosioides and Cymbopogon nardus resulted in 80%–90% mortality of coffee berry borer, whereas essential oils of C. ambrosioides, T. vulgaris and R. chalepensis achieved 87.5%–92.5% mortality of antestia bug. Essential oils of C. ambrosioides caused significantly the highest percentage mortality of the maize weevils (95%) with “Lethal Dose” (LD50) values of 2.202 ml 100 ml−1 within 24 h after treatment, whereas essential oils of Mentha spicata, T. vulgaris and R. chalepensis resulted in 82.5%, 77.5% and 73.5% mortality, respectively. The potential of plant essential oils for the management of coffee berry borer, antestia bug and maize weevil for the small-scale farmers is discussed.