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.The Centre de CoopeÂration Internationale en Recherche Agronomique pour le DeÂveloppement (CIRAD), Montpellier, France, https://www.cirad.fr/, in support of PhD student stipend (AGAA); CHIESA project (Climate Change Impacts on Ecosystem Services and Food Security in Eastern Africa) funded by the Ministry of Foreign Affairs of Finland, http://chiesa.icipe. org/, in support of laboratory and field experimentation; The German Academic Exchange Service (DAAD) In-Region Postgraduate Scholarship, in support of student stipends and school fees. International Centre of Insect Physiology and Ecology is core-funded by UK's Department for International Development (DFID), Swedish International Development Cooperation Agency, the Swiss Agency for Development and Cooperation (SDC) and the Kenyan Government.http://www.plosone.orgam2018Zoology and Entomolog

Temperature-dependent development and survival of immature stages of the coffee berry borer Hypothenemus hampei (Coleoptera: Curculionidae)

Although the coffee berry borer, Hypothenemus hampei (Ferrari) (Coleoptera: Curculionidae: Scolytinae) is the most destructive insect pest of coffee worldwide, there is much to learn about its thermal biology. This study aimed to develop temperature-based models for H. hampei development and to provide the thermal requirements of immature stages in the laboratory. Using a new observation method, larval development and survival were monitored daily on fresh Arabica coffee seeds, under seven constant temperatures in the range 15–35°C, with 80 ± 5% RH and 12:12 L:D photoperiod. Linear and non-linear functions were fitted to the development data plotted against temperature, using Insect Life Cycle Modelling software (ILCYM). Temperature significantly affected the development time of all immature stages. Egg incubation period ranged 4.6–16.8 days, under temperature between 30 and 15°C. No development occurred at 35°C and the larval stage did not develop to pupa at 15°C. The minimum temperature threshold (Tmin) estimated from linear regression was 10.5, 13.0, 15.0 and 13.0°C, for egg, larva, pupa and the total development from egg to adult, respectively. The maximum temperature threshold (Tmax) estimated from the Sharpe and DeMichele function was 32°C for egg to adult development. The thermal constant (k) was estimated at 78.1, 188.7, 36.5 and 312.5 degree days, for egg, larva, pupa and for egg to adult, respectively. Our results will help understand and predict the pest population dynamics and distribution in coffee plantations as impacted by temperature, and as such, will contribute to a more efficient management of the pest.The Centre de Coopération Internationale en Recherche Agronomique pour le Développement (CIRAD), Montpellier, France; UK’s Department for International Development (DFID); Swedish International Development Cooperation Agency (Sida); the Swiss Agency for Development and Cooperation (SDC); and the Kenyan Government. The first author AGA Azrag was supported by a German Academic Exchange Service (DAAD) In-Region Postgraduate Scholarship as well as the National research foundation of South Africa to AA Yusuf & CWW Pirk.https://www.cambridge.org/core/journals/bulletin-of-entomological-research2020-02-23hj2019Zoology and Entomolog