Influence of Production System, Shade Level and Altitudinal Gradient on the Abundance of Urticating ant on Coffee in Southwestern Ethiopia

Abstract

Urticating ant, also referred to as biting ant, Tetramorium aculeatum Mayr, is an important pest in coffee and becoming a constant problems for the farmers affecting farming activities in Southwestern Ethiopia. Urticating ants are not directly affecting coffee crop, but hindering the agronomic and ripe berry picking activities. As a result ripe coffee beans stay longer in the field and subjected to deterioration. This study assessed the influence of coffee production systems, shade level, and altitudes on the abundance of urticating ant in coffee farms among coffee-producing areas in Southwestern Ethiopia. The study was set as 3x3 factorial and replicated three times considering production system with shade level and again production system with altitude ranges as factors and farms as a replication. Twenty to forty coffee trees were randomly assessed in each farm. The results showed that varying numbers of urticating ant nests were observed on coffee trees among the three coffee production systems, shade coverage level and altitudinal gradients. Production systems in respect to shade levels had a highly significant influence (p < 0.0001) on the abundance of the urticating ant on coffee trees. Coffee trees in plantation production system with heavy shade level had significantly higher mean number of nests per coffee tree (17.25 ± 7.9) compared to the garden and semi-forest coffee in Southwestern Ethiopia. The present study also showed that coffee production system with altitudinal gradient had a highly significant (p = 0.005) effects on the abundance of nests on coffee trees. The urticating ant constructed the highest number of nests (20.10 ± 15.1) on coffee trees in plantation farms under lowland altitudes. Minimum temperature (r = 0.61*) and shade level (r = 0.56*) showed significantly positive correlations to infestation by urticating ant whereas altitude (r = - 0.57*) is negatively correlated with ant abundance. In conclusion, this study revealed population of urticating ant nests varied among coffee production systems, shade levels and altitudinal gradients. In addition, it strongly suggests the abundance of urticating ant is dependent on microclimatic conditions of coffee agro-ecosystems. However, we recommend future study on the ecological role of urticating ant, ecological service or disservice provider to coffee ecosystem, and also this study calls up further studies on the bio-ecology and integrated management methods as it has implication on coffee yield loss.