Abstract:
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.
