In vitro inhibitory effect of selected fungicides on mycelial growth of ambrosia fungus associated with the black coffee twig borer, Xylosandrus compactus Eichhoff (Coleoptera: Curculionidae) in Uganda

Black coffee twig borer is a new but rapidly spreading insect pest of coffee in Uganda. Female beetles bore into primary branches/twigs and cultivate an ambrosia fungus for feeding their larvae. Thus, controlling the fungus means depriving the brood a source of food. Three fungicides, chlorothalonil (Glider), tebuconazole (Orius 25EW) and dimethomorph + mancozeb (Volar) were evaluated in vitro for their effectiveness in inhibiting mycelial growth of ambrosia fungus associated with the beetle. The pathogen was exposed to four concentrations (1.5x, 1.25x, 1.0x and 0.5x times the manufacturer recommended rate) incorporated into potato dextrose agar using inhibition and food poisoning techniques. The three fungicides inhibited fungal growth to some extent, even at the lowest concentration (0.5x) and percentage inhibition was significantly different (P≤0.05) from each other. Tebucozanole caused 100% growth inhibition irrespective of concentration and technique used while chlorothalonil and dimethomorph + mancozeb caused less than 40% inhibition for both techniques. Therefore, research should determine effectiveness of tebucozanole for suppressing fungal growth under field conditions for diminishing beetle incidence and fungal pathogenic effects in infested branches. This will pave way for integration of use of tebucozanole into overall Integrated Pest Management package (IPM) for the beetle in Uganda. (Résumé d'auteur

Forest Landscapes Influence Black Coffee Twig Borer, Xylosandrus compactus Eichoff Infestation in Adjacent Robusta Coffee Gardens: Management Implications

The black coffee twig borer, Xylosandrus compactus Eichhoff (Coleoptera: Curculionidae) is one of the major constraints facing the Robusta coffee industry in Uganda since its advent in 1993. Once in a new location, it spreads rapidly within and between coffee gardens. This is mainly driven by favorable climatic conditions, presence of alternate hosts, limited management by farmers and the fact that natural enemies present in the new eco-systems are yet to adapt to it. Its management is difficult due to its cryptic nature of spending almost its entire lifespan is spent inside the host galleries. X. compactus has >200 host plant species worldwide, whereas, >50 plant species have been proven to be hosts in Uganda including: - commercial and ornamental crops as well as shade and forest trees/shrubs. In addition, these trees provide shady conditions that promote infestation of this pest. A study was therefore conducted in central Uganda to elucidate the effects of forest landscapes on the distribution of X. compactus damage in the adjoining Robusta coffee gardens. New alternate host plants of X. compactus within the forests were also documented. This could inform further development of its management strategy Uganda. Results showed that the percentage of coffee suckers and primary branches infested by X. compactus increased significantly (p=0.0171 and p=0.0001 respectively) with increasing distance away from the forest edge towards the center of the forest. The percentage infestation however decreased significantly (p<.0001 and p=0.2367) for suckers and primary branches respectively with increasing distance from forest edge towards the center of the adjoining coffee plantation. These observations are explicable by the fact that the forest acts as a source of X. compactus infestation for the adjoining coffee plantation, commonly referred to as “pull-effect”, the nearer the coffee trees to the forest the greater the initial infestation. Nine alternative host plant species, namely: - charcoal tree Trema orientalis Linn. Blume (Ulmaceae), African celtis, Celtis mildbraedii Engl. (Ulmaceae), bastard-wild-rubber, Funtumia africana Benth. Stapf (Apocynaceae), velvet-leaved combretum, Combretum molle R. Br. Ex. G. Don. Engl & Diels (Combretaceae) and five unidentified tree species were recorded in the forest. These tree/shrub species have been added to the existing inventory of X. compuctus alternate host plants in Uganda. This study clearly demonstrates the influence of natural forest landscapes on incidence and damage of X. compactus infestations in adjoining Robusta coffee gardens. The results suggest that farmers with coffee gardens neighboring forested landscapes should take into account managing the source of X. compactus infestation from natural forests as well as that on coffee and alternate hosts in their gardens. NARO-BCTB traps should therefore be deployed along the forest boundaries in order to intercept the X. compactus from the forests before they enter the coffee gardens. However, there is need to fully elucidate the interactions between the ‘pull-effect’ and landscape and aggregation factors that influence incidence and damage of X.  compactus attacks so as to inform its management

Towards a collaborative research: A case study on linking science to farmers' perceptions and knowledge on Arabica coffee pests and diseases and its management

The scientific community has recognized the importance of integrating farmer's perceptions and knowledge (FPK) for the development of sustainable pest and disease management strategies. However, the knowledge gap between indigenous and scientific knowledge still contributes to misidentification of plant health constraints and poor adoption of management solutions. This is particularly the case in the context of smallholder farming in developing countries. In this paper, we present a case study on coffee production in Uganda, a sector depending mostly on smallholder farming facing a simultaneous and increasing number of socio-ecological pressures. The objectives of this study were (i) to examine and relate FPK on Arabica Coffee Pests and Diseases (CPaD) to altitude and the vegetation structure of the production systems; (ii) to contrast results with perceptions from experts and (iii) to compare results with field observations, in order to identify constraints for improving the information flow between scientists and farmers. Data were acquired by means of interviews and workshops. One hundred and fifty farmer households managing coffee either at sun exposure, under shade trees or inter-cropped with bananas and spread across an altitudinal gradient were selected. Field sampling of the two most important CPaD was conducted on a subset of 34 plots. The study revealed the following findings: (i) Perceptions on CPaD with respect to their distribution across altitudes and perceived impact are partially concordant among farmers, experts and field observations (ii) There are discrepancies among farmers and experts regarding management practices and the development of CPaD issues of the previous years. (iii) Field observations comparing CPaD in different altitudes and production systems indicate ambiguity of the role of shade trees. According to the locality-specific variability in CPaD pressure as well as in FPK, the importance of developing spatially variable and relevant CPaD control practices is proposed. (Résumé d'auteur

Field-based Evidence of the Black Coffee Twig Borer infesting Maesopsis eminii in Coffee Agro-systems in Kiboga District, Uganda

Despite Ugandan coffee farmers’ preference for Maesopsis eminii as a shade tree, the species is an alternate host for the black coffee twig borer, Xylosandrus compactus (Eichhoff)—a major insect pest of coffee in the country. Wilting and drying of leaves and branches of young M. eminii trees (&lt;5 m tall) observed in Kiboga District, Uganda. The branches were trimmed off the trees, separated into primary and secondary branches and then the percentage of those possessing characteristic X. compactus entry holes determined separately. Additionally, the number of entry holes on both primary and secondly branches was established to determine the extent of damage of X. compactus. X. compactus characteristic holes were observed on both primary and secondary branches of M. eminii - percentage of branches having entry holes and the number of entry holes higher on primary than secondary branches. Dissecting the branches at the entry holes revealed various life stages of X.compactus in the gallery, proving that the damage was due to the pest. Presence of this pest on trees that are inter-planted in the coffee agroforestry systems presents a dilemma in managing it. Therefore, research should be geared towards designing management strategies for the pest in the coffee agroforestry systems. In the meantime, farmers should always trim-off and burn all infested parts from coffee and other plants inter-planted in it.</jats:p

Field-based Evidence of the Black Coffee Twig Borer infesting Maesopsis eminii in Coffee Agro-systems in Kiboga District, Uganda

Despite Ugandan coffee farmers’ preference for Maesopsis eminii as a shade tree, the species is an alternate host for the black coffee twig borer, Xylosandrus compactus (Eichhoff)—a major insect pest of coffee in the country. Wilting and drying of leaves and branches of young M. eminii trees (&lt;5 m tall) observed in Kiboga District, Uganda. The branches were trimmed off the trees, separated into primary and secondary branches and then the percentage of those possessing characteristic X. compactus entry holes determined separately. Additionally, the number of entry holes on both primary and secondly branches was established to determine the extent of damage of X. compactus. X. compactus characteristic holes were observed on both primary and secondary branches of M. eminii - percentage of branches having entry holes and the number of entry holes higher on primary than secondary branches. Dissecting the branches at the entry holes revealed various life stages of X.compactus in the gallery, proving that the damage was due to the pest. Presence of this pest on trees that are inter-planted in the coffee agroforestry systems presents a dilemma in managing it. Therefore, research should be geared towards designing management strategies for the pest in the coffee agroforestry systems. In the meantime, farmers should always trim-off and burn all infested parts from coffee and other plants inter-planted in it

Knowledge Gaps between Farmers and Scientists: A Case Study on Perceptions and Knowledge on Arabica Coffee Pests and Diseases of Mount Elgon, Uganda

In this paper, we present a case study on coffee production in Uganda, a sector depending mostly on smallholder farming facing a simultaneous and increasing number of socio-ecological pressures. The objectives of this study were (i) to examine and relate FPK on Arabica Coffee Pests and Diseases (CPaD) to altitude and the vegetation structure of the production systems; (ii) to contrast results with perceptions from experts and (iii) to validate results with field observations, in order to identify constraints for improving information flow from scientists to farmers and back. The presented study was conducted in the framework of the BMZ-funded project entitled “Trade-offs and synergies in climate change adaptation and mitigation in coffee and cocoa systems”. The GOAL of the project is the adaptation of vulnerable coffee/cocoa-based farming systems to climate change that combine improving farmer income and system resilience with contributing to climate change adaptation and mitigation. The PURPOSE is the adoption of new production technologies in cocoa/coffee-based smallholder farming systems that (i) are adapted to climate change, (ii) contribute to climate change mitigation, (iii) sustain the natural resource base, and (iv) respond to livelihoods needs and constraints.</P

High Robusta coffee plant density is associated with better yield potential at mixed responses for growth robustness, pests and diseases: which way for a farmer?

Plant density in Robusta coffee is an unresolved issue in low volume producing countries especially when compared with leading producers. In this study, we aimed to compare the response of Robusta coffee to pest incidence, disease severity, growth and yield potential in two contrasting spacing regimes. Two spacing regimes of 3mx3m and 3mx1m were evaluated for selected parameters in a randomized complete block design with three replications. There was a highly significant difference in pest incidence between the spacing regimes (p&lt;0.01) for all the pests except scales (p=0.126). The black coffee trig borer incidence was higher under close spacing of 3mx1m than for 3mx3m with a mean difference of 13.2%. There was no significant association between spacing regime and leaf rust disease incidence while the association was significant for red blister disease (χ2=33.56, df=1, p&lt;0.001). Significant difference in growth response between spacing regimes (p&lt;0.05) were also obtained for change in canopy height (dCAH), number of primaries, number of stems and leaf size. For instance, dCAH was higher under 3mx1m spacing than for 3mx3m spacing. A significant difference in yield potential existed between the spacing regimes (p&lt;0.05) for average yield per tree and average yield per hectare (aYH). Close spacing produced a higher aYH (5.82 t cc/ha) than wide spacing (4.80 t cc/ha). Whereas yield potential is high at high tree densities, associated prevalence of biotic constraints calls for supportive stress management package for farmers.</jats:p

A review of the status and progress in management research of the black coffee twig borer, Xylosandrus compactus (Eichhoff) in Uganda

Coffee is the backbone of Uganda's economy, contributing about 18% of foreign exchange earnings valued at US$446 annually. Additionally, nearly 15 million people, draw their livelihood from from coffee-related activities along the value chain. Currently, production of the crop is threatened by a relatively new pest, the black coffee twig borer, Xylosandrus compactus, (Eichhoff) (Coleoptera: Scolytidae). (Here-after referred to as BCTB). A country-wide survey conducted during 2012/13 showed that the pest is rapidly spreading from its secondary epicenter in Kayunga and Mukono districts (Central Uganda) to most of the Robusta coffee growing regions of the country. The survey results further revealed 8.6$40 million annually at the current market prices and production volumes. In related studies, higher BCTB incidences and damage was recorded on shaded than on un-shaded coffee trees. In addition, suveys for its alternate hosts revealed that more than 30 plant species which are commonly intercropped in coffee are alternative hosts of BCTB. These include shade trees like Albizia spp. that have been actively promoted for their excellent shade structure and nitrogen-fixing capacity. Being a relatively new coffee pest in Uganda, there is generally limited information on BCTB and its management. Research efforts to-date have focused on surveillance of its spread and impact with a view of preventing further spread to new areas and minimizing its impact in already infested ones, identifying bio-ecological drivers of its population dynamics, and developing integrated pest management (IPM) packages for its management. A preliminary IPM package has been assembled for use by coffee farmers. This combines community-based phyto-sanitary actions and chemical sprays using imidocloprid (IMAXI or KOHINOR or CONFIDOR) mixed with tebucozanole (ORIUS), eliminating known alternate hosts (including Albizia spp.), proper management of shade trees and coffee canopies, and proper soil fertility and soil moisture management. Future research strategies for better management of BCTB are briefly discussed here. (Résumé d'auteur

Negative-binomial model results examining individual and interaction effects of altitude range and production system on CBD intensity.

Negative-binomial model results examining individual and interaction effects of altitude range and production system on CBD intensity.</p

List of Coffee pests and diseases (CPaD) used in interview survey.

List of Coffee pests and diseases (CPaD) used in interview survey.</p