Coffee accounts for over 20% of Tanzania’s income from foreign exchange and has been identified as an essential
crop for the future of food security in Africa. Coffee production in the Kilimanjaro region, one of Tanzania’s most
important coffee-producing areas, is facing threats due to declining coffee prices, climate change, and outbreaks
of fungal disease. Fungal-resistant hybrid coffee varieties have the potential to increase productivity and yields,
although the ecological impact of their widespread introduction has not yet been determined. This study estimates
the differences in aphid abundance and probability of aphid presence on hybrid and non-hybrid coffee plants in
the Chagga homegardens. For this study, 1,119 coffee plants were sampled in 45 farms across 3 villages in the
Kilimanjaro region. Hybrid coffee plants were 74.7% less likely to have the fungal disease coffee leaf rust (CLR)
than non-hybrid plants (p<0.001). However, hybrid status was not found to be a significant factor in predicting aphid
presence (p=0.88) or abundance (p=0.71). Factors that were significant in predicting aphid abundance included farm
size (p<0.001), insecticide use (p<0.001), village (p=0.001), and ant count (p<0.001). The results of this study suggest
that hybrid coffee has no significant bottom-up effect on the dynamics of the Chagga homegarden ecosystem.