Host-plant and insect-pest compensations, and microclimate as drivers for intensity of Toxoptera aurantii (Hemiptera: Aphididae) in Arabica coffee-banana farming system of mount Elgon region, Uganda

Abstract

Host-plants and insect-pests’ compensational relationships are known to enable plants and insects to survive and adopt to changing environmental conditions. In the mount Elgon region of Uganda, exists a mosaical pattern of different coffee farming systems with increasing altitudes, and their combinations create differing microclimates, which influence host-plant and pest behaviors. The objective of this study was to determine the host-plant and Toxoptera aurantii compensations in Arabica coffee cropping systems of mount Elgon region in Uganda. A two-year study on the coffee leaf biomass, T. aurantii numbers on the leaf surface, and damage intensity of T. aurantii, was conducted using 72 Arabica coffee farms with mixed coffee polycultures (farming systems). Two independent factors were considered; altitude as a major factor and the farming system as the second factor. There was evidence of significant host-plant and insect-pest compensations; host-plant/microclimates, and insect-pest /microclimates. Linear regression analysis revealed a - relationship (number of leaves /branch / T. aurantii numbers). A + relationship (number of leaves / branch infested by T. aurantii / T. aurantii abundance). Also T. aurantii abundance had a + relationship / RH or/ambient temperature). The Arabica coffee leaves/ branch had a – relationship (ambient temperature or/ RH). While the T. aurantii infested leaves /branch only had a + relationship with RH. Regarding the soil variables it was only soil temperature which had a + relationship with the number of leaves /branch. The T. aurantii infested leaves /branch had a + relationship (soil temperature or/soil moisture).