Christian Borgemeister

Some Like It Hot: The Influence and Implications of Climate Change on Coffee Berry Borer (Hypothenemus hampei) and Coffee Production in East Africa

The negative effects of climate change are already evident for many of the 25 million coffee farmers across the tropics and the 90 billion dollar (US) coffee industry. The coffee berry borer (Hypothenemus hampei), the most important pest of coffee worldwide, has already benefited from the temperature rise in East Africa: increased damage to coffee crops and expansion in its distribution range have been reported. In order to anticipate threats and prioritize management actions for H. hampei we present here, maps on future distributions of H. hampei in coffee producing areas of East Africa. Using the CLIMEX model we relate present-day insect distributions to current climate and then project the fitted climatic envelopes under future scenarios A2A and B2B (for HADCM3 model). In both scenarios, the situation with H. hampei is forecasted to worsen in the current Coffea arabica producing areas of Ethiopia, the Ugandan part of the Lake Victoria and Mt. Elgon regions, Mt. Kenya and the Kenyan side of Mt. Elgon, and most of Rwanda and Burundi. The calculated hypothetical number of generations per year of H. hampei is predicted to increase in all C. arabica-producing areas from five to ten. These outcomes will have serious implications for C. arabica production and livelihoods in East Africa. We suggest that the best way to adapt to a rise of temperatures in coffee plantations could be via the introduction of shade trees in sun grown plantations. The aims of this study are to fill knowledge gaps existing in the coffee industry, and to draft an outline for the development of an adaptation strategy package for climate change on coffee production. An abstract in Spanish is provided as Abstract S1.

Shifts in malaria vector species composition and transmission dynamics along the Kenyan coast over the past 20 years

BackgroundOver the past 20 years, numerous studies have investigated the ecology and behaviour of malaria vectors and Plasmodium falciparum malaria transmission on the coast of Kenya. Substantial progress has been made to control vector populations and reduce high malaria prevalence and severe disease. The goal of this paper was to examine trends over the past 20 years in Anopheles species composition, density, blood-feeding behaviour, and P. falciparum sporozoite transmission along the coast of Kenya.MethodsUsing data collected from 1990 to 2010, vector density, species composition, blood-feeding patterns, and malaria transmission intensity was examined along the Kenyan coast. Mosquitoes were identified to species, based on morphological characteristics and DNA extracted from Anopheles gambiae for amplification. Using negative binomial generalized estimating equations, mosquito abundance over the period were modelled while adjusting for season. A multiple logistic regression model was used to analyse the sporozoite rates.ResultsResults show that in some areas along the Kenyan coast, Anopheles arabiensis and Anopheles merus have replaced An. gambiae sensu stricto (s.s.) and Anopheles funestus as the major mosquito species. Further, there has been a shift from human to animal feeding for both An. gambiae sensu lato (s.l.) (99% to 16%) and An. funestus (100% to 3%), and P. falciparum sporozoite rates have significantly declined over the last 20 years, with the lowest sporozoite rates being observed in 2007 (0.19%) and 2008 (0.34%). There has been, on average, a significant reduction in the abundance of An. gambiae s.l. over the years (IRR = 0.94, 95% CI 0.90–0.98), with the density standing at low levels of an average 0.006 mosquitoes/house in the year 2010.ConclusionReductions in the densities of the major malaria vectors and a shift from human to animal feeding have contributed to the decreased burden of malaria along the Kenyan coast. Vector species composition remains heterogeneous but in many areas An. arabiensis has replaced An. gambiae as the major malaria vector. This has important implications for malaria epidemiology and control given that this vector predominately rests and feeds on humans outdoors. Strategies for vector control need to continue focusing on tools for protecting residents inside houses but additionally employ outdoor control tools because these are essential for further reducing the levels of malaria transmission.

Thermal Tolerance of the Coffee Berry Borer Hypothenemus hampei: Predictions of Climate Change Impact on a Tropical Insect Pest

Coffee is predicted to be severely affected by climate change. We determined the thermal tolerance of the coffee berry borer , Hypothenemus hampei, the most devastating pest of coffee worldwide, and make inferences on the possible effects of climate change using climatic data from Colombia, Kenya, Tanzania, and Ethiopia. For this, the effect of eight temperature regimes (15, 20, 23, 25, 27, 30, 33 and 35°C) on the bionomics of H. hampei was studied. Successful egg to adult development occurred between 20–30°C. Using linear regression and a modified Logan model, the lower and upper thresholds for development were estimated at 14.9 and 32°C, respectively. In Kenya and Colombia, the number of pest generations per year was considerably and positively correlated with the warming tolerance. Analysing 32 years of climatic data from Jimma (Ethiopia) revealed that before 1984 it was too cold for H. hampei to complete even one generation per year, but thereafter, because of rising temperatures in the area, 1–2 generations per year/coffee season could be completed. Calculated data on warming tolerance and thermal safety margins of H. hampei for the three East African locations showed considerably high variability compared to the Colombian site. The model indicates that for every 1°C rise in thermal optimum (Topt.), the maximum intrinsic rate of increase (r max) will increase by an average of 8.5%. The effects of climate change on the further range of H. hampei distribution and possible adaption strategies are discussed. Abstracts in Spanish and French are provided as supplementary material Abstract S1 and Abstract S2.

Monitoring and Modeling of Field Infestation and Damage by the Maize Ear Borer Mussidia nigrivenella (Lepidoptera: Pyralidae) in Benin, West Africa

Abstract In many countries in West Africa, the pyralid ear borer Mussidia nigrivenella Ragonot occasionally causes severe damage to pre- and postharvest maize. Between 1992 and 1995, the distribution of and damage caused by M. nigrivenella were studied in Benin using survey data and an on-station field experiment. The borer was distributed across the whole country, and at maturity an average 25% of the ears sampled in maize fields were infested. Damage levels varied with agro-ecological zones and were highest in the Guinea Savannas. However, borer-related yield losses were comparatively low. Three applications of cypermethrin over the growing season did not provide sufficient control in the on-station field experiment. A model was developed to estimate maize losses caused by M. nigrivenella, using the percentage of infested ears, which explained 93% of the variance. Extrapolation of field data indicated a 25% yield loss once a 100% infestation of maize ears was reached. For surveys in maize fields the model is a valid tool for a rapid assessment of crop losses caused by M. nigrivenella.

Effects of neonicotinoid insecticides on the bionomics of twospotted spider mite (Acari: Tetranychidae)

Abstract Previous reports indicate that applications of imidacloprid, a neonicotinoid insecticide, can lead to population buildups of twospotted spider mite, Tetranychus urticae Koch, in the field. Moreover, laboratory studies showed enhanced fecundity of T. urticae after an imidacloprid treatment. In this study, experiments were conducted in the greenhouse to investigate the potential effects of imidacloprid and several other neonicotinoid insecticides on fecundity, egg viability, preimaginal survivorship, and sex ratio of T. urticae (German strain WI) on French beans, Phaseolus vulgaris L. Four insecticides, i.e., imidacloprid (Confidor 200SL), thiacloprid (Calypso 480 SC), acetamiprid (Mospilan 70 WP), and thiamethoxam (Actara 25 WG), were tested at field-relevant (100, 120, 125, and 95 ppm) and sublethal doses (10, 12, 12.5, and 9.5 ppm), respectively. Both spray and drench applications were tested. At field-relevant doses, fecundity of T. urticae decreased and was lower in the treatments compared with the untreated control, whereas preimaginal survivorship and proportion of female offspring (i.e., sex ratio) were lower compared with the control. At sublethal doses, no significant differences were found among the treatments. Data on egg viability, preimaginal survivorship, and sex ratio at sublethal doses followed the same trends as at field-relevant doses. In an additional experiment, the metabolism of imidacloprid into monohydroxy-imidacloprid, olefine, guanidine, and 6-chloronicotinic acid was compared with the oviposition pattern of T. urticae. These findings are discussed with regard to previous laboratory and field observations of imidacloprid-induced fertility increases in T. urticae.

Factors Affecting Infestations of the Stalk Borer Busseola fusca (Lepitoptera: Noctuidae) on Maize in the Forest Zone of Cameroon with Special Reference to Scelionid Egg Parasitoids

Abstract The effect of vegetation, intercropping, and Telenomus spp. egg parasitism during the vegetative stage of maize on Busseola fusca (Fuller) (Lepitoptera: Noctuidae) infestations and maize yields at harvest were studied during two consecutive cropping seasons, in the humid forest zone of Cameroon. Six locations grouped into three blocks, representing gradients in human population densities of 15–88 inhabitants/km2 were chosen. The fields were located at 20–90 min walking distance from the next road. Differences between blocks in the measured variables were mostly not significant indicating that the population density gradient was not strong enough to affect length of fallow period and thereby vegetation, the population dynamics of pests and natural enemies, and maize yields in forest fields. Numbers of egg batches per plant but also egg parasitism by and sex ratio of Telenomus spp. were significantly higher during the second than the first season (66.9 versus 19.9% and 0.67 versus 0.21, respectively). As a result, the number of borers per plant was only 0.22 versus 0.73 during the first season. Similarly, total mortality of immature B. fusca was 60.5% during the first and 93.2% during the second season. The seasonal differences in unexplained mortality was probably because rainfall caused drowning of migrating first instars. High mean parasitoid mortality at the beginning of the first season was probably caused by high superparasitism promoted by low host density conditions. Across seasons, abundance of grasses in the surroundings of a field was negatively related to egg batch density. Likewise, numbers of B. fusca decreased with increasing density of the nonhost cassava in the field, indicating increasing mortality of migrating larvae. Egg numbers per plant was negatively and egg parasitism or parasitoid sex ratio was positively related to yield.

Plasmodium falciparum Infection Increases Anopheles gambiae Attraction to Nectar Sources and Sugar Uptake

Plasmodium parasites are known to manipulate the behavior of their vectors so as to enhance transmission. From an evolutionary standpoint, behavior manipulation by the parasite should expose the vector to limited risk of early mortality while ensuring sufficient energy supply for both it and the vector. However, it is unknown whether this vector manipulation also affects vector-plant interaction and sugar uptake. Here, we show that the attraction of Anopheles gambiae s.s. to plant odors increased by 30% and 24% after infection with the oocyst and sporozoite stages of Plasmodium falciparum, respectively, while probing activity increased by 77% and 80%, respectively, when the vectors were infected with the two stages of the parasite. Our data also reveal an increased sugar uptake at the oocyst stage that decreased at the sporozoite stage of infection compared to uninfected An. gambiae, with depletion of lipid reserves at the sporozoite stage. These results point to a possible physiological adjustment by An. gambiae to P. falciparum infection or behavior manipulation of An. gambiae by P. falciparum to enhance transmission. We conclude that the nectar-seeking behavior of P. falciparum-infected An. gambiae appears to be modified in a manner governed by the vectors fight for survival and the parasites need to advance its transmission.

Laboratory investigations on the potential of entomopathogenic fungi for biocontrol of Helicoverpa armigera (Lepidoptera: Noctuidae) larvae and pupae

Abstract The susceptibility of third instar Helicoverpa armigera to seven strains of three entomopathogenic fungal species, i.e. Metarhizium anisopliae, Beauveria bassiana and Paecilomyces fumosoroseus, was tested under laboratory conditions using the larval immersion method. High efficacies ranging from 68 to 100% corrected mortality were recorded with more profound effects in treatments with B. bassiana and P. fumosoroseus strains. The median lethal concentration (LC50) for L3 was 6.0×105 in M. anisopliae 79, 1.5×105 in B. bassiana 124 and 4.2×104 in P. fumosoroseus 14. These three strains were further used to characterize the age-dependent mortality of different larval stages (L2–L5) and the effect against pupae of H. armigera. Larval stages did not differ in their mortality but differed i in median lethal time, with shorter values recorded in the second instar. Tested fungi also caused a high reduction between 74.4 and 100% in the emergence of pupae using the soil inoculation method and the pupal immersion technique. All three fungal species, especially P. fumosoroseus, have a high potential for biocontrol of H. armigera larvae and also as a soil treatment targeting the pupae.

Climate Change or Urbanization? Impacts on a Traditional Coffee Production System in East Africa over the Last 80 Years

Global environmental changes (GEC) such as climate change (CC) and climate variability have serious impacts in the tropics, particularly in Africa. These are compounded by changes in land use/land cover, which in turn are driven mainly by economic and population growth, and urbanization. These factors create a feedback loop, which affects ecosystems and particularly ecosystem services, for example plant-insect interactions, and by consequence agricultural productivity. We studied effects of GEC at a local level, using a traditional coffee production area in greater Nairobi, Kenya. We chose coffee, the most valuable agricultural commodity worldwide, as it generates income for 100 million people, mainly in the developing world. Using the coffee berry borer, the most serious biotic threat to global coffee production, we show how environmental changes and different production systems (shaded and sun-grown coffee) can affect the crop. We combined detailed entomological assessments with historic climate records (from 1929–2011), and spatial and demographic data, to assess GECs impact on coffee at a local scale. Additionally, we tested the utility of an adaptation strategy that is simple and easy to implement. Our results show that while interactions between CC and migration/urbanization, with its resultant landscape modifications, create a feedback loop whereby agroecosystems such as coffee are adversely affected, bio-diverse shaded coffee proved far more resilient and productive than coffee grown in monoculture, and was significantly less harmed by its insect pest. Thus, a relatively simple strategy such as shading coffee can tremendously improve resilience of agro-ecosystems, providing small-scale farmers in Africa with an easily implemented tool to safeguard their livelihoods in a changing climate.

Taxonomy, Ecology, and Management of Native and Exotic Fruit Fly Species in Africa

Horticulture is one of the most important agricultural subsectors in Africa, providing income, creating employment opportunities, and enhancing food and nutritional security. However, tephritid fruit flies are responsible for both direct and indirect losses, with alien invasive species often having the most severe ecological and economic impact. In the past 20 years, systematic analysis of tephritids has provided comparative information on taxonomy, synonymy, and character-state differentiation. New molecular techniques are now available for identifying species, reconstructing phylogenies, and studying population genetic structures. Research on biology, host range and shifts, thermotolerance, and demography has provided useful information for developing predictive and ecological niche models to guide management methods. In recent years, the responses of various species to attractants have been documented. Several suppression methods, including the release of coevolved parasitoid species targeting invasives, have been promoted within the context of integrated pest management, leading to improvement in the quality and quantity of fruits and vegetables produced. However, there is still the need for wide-scale availability of these technologies to smallholder growers across Africa.