Impact of agricultural practices on the population dynamics of African weaver ant Oecophylla longinoda Latreille in cashew agroecosystems in Tanzania

Abstract

Arboreal ants play a crucial role in maintaining the stability of agroecosystems, contributing to pest regulation and serving as indicators of environmental health. Understanding the impact of agricultural practices on African weaver ant (AWA) populations is essential for optimising their beneficial effects. However, the correlation between these practices and AWA abundance in cashew orchards remains poorly understood. This study aimed to examine the effects of weed management and pruning practices on AWA populations in cashew orchards. The experiments were conducted over two years in two cashew fields at each of two locations (Chambezi and Mwanambaya), using a randomised complete block design. Three treatments were applied: unweeded plots serving as the control (T 1 ), weeded plots (T 2 ), and pruned plots (T 3 ). The abundance of AWA was monitored during both the on-season and off-season, based on the percentage of AWA trails and the number of nests observed per tree. The results showed that AWA abundance was generally minimal during the cashew off-seasons. However, it varied significantly during the on-season in both the unweeded and weeded plots, with the pruned plot being the exception. For instance, in Chambezi, the highest levels of AWA trails were recorded in the unweeded plot (62.5%), followed by the weeded plot (55.2%), while the pruned trees had the lowest level (33.5%). Similarly, in Chambezi, the mean number of leaf nests per tree was highest in the unweeded plot (17.2), followed by the weeded plot (15.3), whereas the pruned plot recorded the lowest mean (7.3). The differences in AWA abundance observed across the two evaluated parameters highlight the significant influence of agronomic practices. These findings suggest that adopting less conventional weeding techniques may enhance biodiversity in cashew agroecosystems. Such strategies are crucial for supporting beneficial insect populations and promoting agricultural sustainability.