Johann Baumgärtner

IMPACT ASSESSMENT OF AN EXOTIC PARASITOID ON STEMBORER (LEPIDOPTERA) POPULATION DYNAMICS IN KENYA

A ratio-dependent host–parasite interaction model with a linear trend was developed to analyze the impact of the exotic parasitoid Cotesia flavipes (Cameron) (Hymenoptera: Braconidae) on stemborer population dynamics in the southern coastal area of Kenya. The time dependence of the host and that between the host and parasitoid were tested using autocorrelation and cross-correlation functions. The criterion for measuring the parasitoid impact was the difference between the model predictions with and without the parasitoid. The results indicated that the suppressive impact of the parasitoid on stemborer densities began in the short rains season of 1997–1998 in the northern part of the coast zone but was only seen in the southern part of the coast beginning with the long rains season of 1999. The density reduction of the total stemborer complex, which includes one alien and two native species, by C. flavipes was 1.05 ± 0.25 larvae per plant in the north coast and 0.62 ± 0.58 larvae per plant in the south coast during the long rains season of 1999. The reduction of the exotic stemborer Chilo partellus (Swinhoe) (Lepidoptera: Crambidae) by C. flavipes was 0.99 ± 0.25 larvae per plant in the north coast in the long rains season of 1999, or a 52.94 ± 13.37% decrease of the C. partellus density. In the south coast, the reduction was 0.83 ± 0.41 larvae per plant or ∼33.07 ± 16.33% decrease in the C. partellus density.

Prospective analysis of the invasive potential of the European grapevine moth Lobesia botrana (Den. & Schiff.) in California

1 The polyphagous European grapevine moth Lobesia botrana (Den. & Schiff.) is the principal native pest of grape berries in the Palearctic region. It was found in Napa County, California, in 2009, and it has subsequently been recorded in an additional nine counties, despite an ongoing eradication programme. The present study aimed to assess prospectively its potential geographical distribution and relative abundance in California and the continental U.S.A. A subsidiary goal was to provide explanation for timing control measures. 2 Data from the European literature were used to formulate and parameterize a holistic physiologically‐based demographic model for L. botrana. This model was linked to an extant mechanistic model of grapevine phenology, growth and development that provides the bottom‐up effects of fruiting phenology, age and abundance on L. botrana dynamics. Fruit age affects larval developmental rates, and has carryover effects on pupal development and adult fecundity. Also included in the model were the effects of temperature on developmental, survival and fecundity rates. 3 Observed daily weather data were used to simulate the potential distribution of the moth in California, and the continental U.S.A. The relative total number of pupae per vine per year was used as the metric of favourability at all locations. The simulation data were mapped using grass gis (http://grass.osgeo.org/). 4 The model predicts L. botrana can spread statewide with the highest populations expected in the hotter regions of southern California and the lower half of the Central Valley. In the U.S.A., areas of highest favourability include south Texas, and much of the southeast U.S.A. 5 The effects of a warmer climate on pest abundance were explored by increasing observed mean temperatures 2° and 3 °C. L. botrana abundance is expected to increase in northern California and in the agriculturally rich Central Valley but to decrease in the hot deserts of southern California where summer temperatures would approach its upper thermal limit. 6 Analysis of the timing of mating disruption pheromone for control of L. botrana suggests the greatest benefit would accrue by targeting adults emerging from winter diapause pupae and the flight of first summer adults.

Development of an Adaptive Tsetse Population Management Scheme for the Luke Community, Ethiopia

Abstract Since 1996, tsetse (Glossina spp.) control operations, using odor-baited traps, have been carried out in the Luke area of Gurage zone, southwestern Ethiopia. Glossina morsitans submorsitans Newstead was identified as the dominant species in the area, but the presence of Glossina fuscipes Newstead and Glossina pallidipes Austen also was recorded. Here, we refer to the combined number of these three species and report the work undertaken from October 2002 to October 2004 to render the control system more efficient by reducing the number of traps used and maintaining the previously reached levels of tsetse occurrence and trypanosomiasis prevalence. This was done by the design and implementation of an adaptive tsetse population management system. It consists first of an efficient community-participatory monitoring scheme that allowed us to reduce the number of traps used from 216 to 127 (107 monitoring traps and 20 control traps). Geostatistical methods, including kriging and mapping, furthermore allowed identification and monitoring of the spatiotemporal dynamics of patches with increased fly densities, referred to as hot spots. To respond to hot spots, the Luke community was advised and assisted in control trap deployment. Adaptive management was shown to be more efficient than the previously used mass trapping system. In that context, trap numbers could be reduced substantially, at the same time maintaining previously achieved levels of tsetse occurrences and disease prevalence.

Towards an improved understanding of the dynamics of vineyard-infesting Scaphoideus titanus leafhopper populations for better timing of management activities

BACKGROUND This paper deals with supervised management of Scaphoideus titanus (Homoptera Cicadellidae) and describes a phenology model designed for improving the understanding of the within-vineyard dynamics and the timing of insect growth regulator (IGR) applications. RESULTS The model consists of five components dealing with (a) the beginning of the post-dormancy development of overwintering eggs, (b) the egg hatching patterns, (c) the duration of first-instar nymphs, (d) the development and survival of subsequent instars and (e) the stochastic development of cohorts and their passage into the adult stage. Laboratory data permitted the parameterisation of temperature-dependent development and survival functions. Field data consisting mainly of beating tray catches allowed model parameterisation and validation. The model satisfactorily predicts the dynamics of age structures, the beginning as well as the pattern of egg hatching, the occurrence of the third instar and the emergence of adults. CONCLUSION The phenology model is useful for timing IGR applications and for setting up monitoring activities in supervised S. titanus control. The model is an entry point into an adaptive management system, in that real-time weather and monitoring data are continuously integrated into the model for improving its explanatory and predictive capabilities.

The relationships between phenolic content, pollen diversity, physicochemical information and radical scavenging activity in honey.

Honey is rich in different secondary plant metabolites acting as natural antioxidants and contributing to human health. Radical scavenging activity (RSA) is related to antioxidant activity, while the correlation between the phenolic content and RSA is often weak. Consequently, exclusive information on phenolics is often insufficient to qualify the RSA and the health promoting effects of honey. The paper deals with a case study of honey samples originating from the alpine areas of Italy’s Lombardia and Veneto regions and realized by standard physicochemical and statistical analytical methods. In pure honey, the total phenolic content and the RSA were measured in spectrophotometric tests with the 2,2-diphenyl-1-picrylhydrazyl (DPPH·) free radical and Folin-Ciocalteu assays, respectively. Melissopalynological data was used to qualify pollen diversity through rank-frequency curves separating the samples into two groups. On the basis of physicochemical data, the samples were analyzed through multivariate classification and ranking procedures resulting in the identification of an outlier. Elimination of the outlier produced a high correlation between the total phenolic content and RSA in the two pollen diversity groups. The case study suggests that, after disregarding outliers, the RSA activity can be satisfactorily qualified on the basis of phenolics with pollen diversity as a covariate.

Adaptive Ecosocial System Sustainability Enhancement in Sub-Saharan Africa

A conceptual framework is developed and used for improving the livelihood of Sub-Saharan communities faced with multiple stresses resulting from adverse environments, vector-transmitted diseases, and limited food. Ecosocial systems are the units for management. The accumulation of ecological, economic, and social capital is the objective of management, the reduction of maintenance costs is the key strategy, and technologies must satisfy ecological, economic, and social criteria. Interacting social system components are communities, facilitators, scientists, and political as well as administrative organizations. An adaptive approach to management allows flexibility in human and financial resource allocation and results in changes in knowledge and efficacy of management operations. The implementation strategy at two sites in Ethiopia relies on a two-stage procedure. In Stage 1, human and cattle health management set the conditions for development. In Stage 2, the ecosocial system is kept on a trajectory to enhanced ecological, economic, and social capital. In each stage, the assignment of responsibilities leads to four implementation phases. In Stage 1, successful precision targeting of tsetse and drug-based Trypanosoma spp. control increased the economic and social capital at the Luke site in southwestern Ethiopia but threatened the ecological capital because of overstocking and land degradation. In Stage 2, a women’s group living in the outskirts of Addis Ababa (Ethiopia) transformed barren land into a horticultural enterprise to enhance ecosystem service provision, including production of horticultural goods, and increase soil fertility expressed by nutrients and water availability. This article reviews concepts on human livelihood improvement in Sub-Saharan Africa and identifies principles that became important during project execution.

Simulation model for maize crop growth based on acquisition and allocation processes for carbohydrate and nitrogen

Abstract A population model for maize growth and development driven by temperature, solar radiation, soil water and soil nitrogen is presented. A time-varying distributed delay model is used to describe the dynamics of the attributes number, biomass and nitrogen belonging to leaf, root, stem, grain, rachys and husk populations. Photosynthate production as well as water and nitrogen acquisition was simulated with a demand-driven ratio-dependent functional response model. Carbohydrate, water and nitrogen supply-demand ratios were calculated to control the growth of different populations of plant. The metabolic pool model was used to allocate carbohydrates to plant subunits. The model was validated with published observations and field data from a 95- and a 120-day variety grown at the Research Station of the International Institute of Tropical Agriculture in Calavi, in the southern part of the Republic of Benin (West Africa). It was concluded to satisfactorily represent crop phenology and growth patterns. Moreover, the model permitted the assessment of drought stress, soil nitrogen, and planting density effects on maize growth and development.

Evaluation of mortality factors and risk analysis for the design of an integrated pest management system

A probabilistic approach of survival analysis based on the theory of competing risks was applied to the potato tuber moth Phthorimaea operculella (Zeller) affecting tubers in Tunisian rustic stores. Exponential curve of death, i.e. constant force of mortality functions were used in a case study on a cohort time basis. The additive property of crude cause-specific forces of mortality is used to combine mortality factors, which permits to judge different control strategies. In an integrated pest management perspective, the effect of basic mortalities, i.e innate and dispersal related mortalities is recombined with native natural enemies. Thereafter, we calculate the force of additional comptatible control factors needed to reduce the proportion of infested tubers below an economically relevant level. Control strategies based on native natural enemies are shown to have variable effects which put farmers at economic risks. The general importance of integrating compatible control factors is recognized in the evaluation of virus applications. Based on risk analyses, Tunisian potato growers were recommended, in the case of standard initial infestations of five eggs per tuber, to use virus preparations at a higher dosage than the 0.0015 larval equivalent/kg as used in this study. Moreover, the study confirms the general importance of entering potatoes with low infestation levels into rustic shelters. This considerably decreases the risk of exceeding the economic threshold and make virus based control efficient even at low dosages. If the initial infestation considerably exceeds five eggs per tuber, the integration of a compatible control factor becomes more difficult. Nevertheless, even in absence of additional control factors the infestation of tubers does not exceed 50%.

Spatial clustering and associations of two savannah tsetse species, Glossina morsitans submorsitans and Glossina pallidipes (Diptera: Glossinidae), for guiding interventions in an adaptive cattle health management framework.

The paper deals with tsetse (family Glossinidae) control and aims at improving the methodology for precision targeting interventions in an adaptive pest management system. The spatio-temporal distribution of Glossina morsitans submorsitans Newstead, and Glossina pallidipes Austen, at Ethiopias Keto pilot site, is analyzed with the spatial analysis by distance indices (SADIE) methodology that focus on clustering and spatial associations between species and between sexes. Both species displayed an aggregated distribution characterised by two main patches in the south and an extended gap in the north. Spatial patterns were positively correlated and stable in most cases, with the exception of the early dry season and the short rainy season when there were differences between the species and sexes. For precision targeting interventions, the presented methods here are more effective than the previously used geostatistical analyses for identifying and delimiting hot spots on maps, measuring shapes and sizes of patches, and discarding areas with low tsetse density. Because of the improved knowledge on hot spot occurrences, the methods allow a better delimitation of the territory for control operations and a more precise computation of the number of the relatively expensive traps used for monitoring and control purposes.

The use of phenology models in plant conservation programmes: the establishment of the earliest cutting date for the wild daffodil Narcissus radiiflorus

A phenology model was developed for the wild daffodil Narcissus radiiflorus growing in alpine meadows. The model is based on temperature-dependent growth rates and on the rate summation method, and represents the development from 1 January to full bloom, i.e. phase I, and from full bloom to 50% fruit maturity, i.e. phase II. Published data obtained in the laboratory and observations made at different altitudes near the villages of Seewis i. P. and Fanas in the canton of the Grisons, Switzerland, were used for estimating model parameters. To conserve N. radiiflorus the first cut should be delayed until completion of phase II. The time in days between full bloom and 50% fruit maturity at different altitudes was simulated by using 16 years of temperature data. These data were recorded at a nearby weather station and adapted to different altitudes by assuming a 0.5°C decrease in temperature for a 100 m increase in altitude. Significant differences between the length of phase II at different altitudes were found. However, in the main areas where Narcissus occurs, a subset of equal mean duration of phase II could be identified. This is explained by the compensation of the altitude-dependent temperature decrease caused by the general increase in temperature during phase II, i.e. in June and July. For this subset the logistic function was fitted to the frequency distribution of the number of days required to complete phase II. When accepting a 10% risk of mowing too early, the first cut should be delayed by 34 days after full bloom. The 34-day rule is considered a more adequate and efficient method to plan meadow management than the method actually used based on predefined calendar days.