Comparative field efficacy of synthetic insecticides and plant extracts against Tuta absoluta (Lepidoptera: Gelechiidae) in Lubumbashi, DR Congo.

The invasive tomato leafminer, Tuta absoluta (Meyrick), is a very destructive pest that poses a major threat to tomato (Solanum lycopersicum L.) production in the Democratic Republic of Congo (DRC), causing extensive yield losses through larval feeding on leaves, stems, and fruits. Chemical insecticides remain the primary control method, but resistance development, biodiversity loss and environmental concerns necessitate alternative strategies. This study aimed at evaluating the efficacy of synthetic and botanical insecticides against T. absoluta during two consecutive cropping seasons 2023-2024 in Lubumbashi, DRC, under both dry and rainy season conditions. Two tomato seedling varieties (Tanya F1 and Tovi Star F1) were treated with four synthetic insecticides (Dudu acelamectin 5% EC, cypermethrin 200 EC, lambda-cyhalothrin 50 EC and Occasion Star 200SC) and two botanical treatments (Tephrosia vogelii extract and Nimbecidine) at the recommended doses in a randomized complete block design. Pest incidence, larval density, leaf damage, and yield were assessed over multiple intervals. Results showed that synthetic insecticides, particularly Dudu acelamectin 5% EC, lambda-cyhalothrin 50 EC, and Occasion Star 200SC, significantly reduced T. absoluta larval infestations compared to cypermethrin 200 EC, which failed to control the pest due to suspected potential resistance. Botanical insecticides were also proved effective, with T. vogelii extract reducing leaf damage by 48% and Nimbecidine by 38%. The Tovi Star F1 variety exhibited inherent resistance, with lower pest incidence and higher yields than Tanya F1. Yield losses were strongly correlated with pest incidence and larval density, emphasizing the need for timely interventions. These findings highlight the potential of integrating synthetic and botanical insecticides with resistant tomato varieties for sustainable T. absoluta management in Lubumbashi. Future research should explore long-term resistance monitoring, cost-benefit analyses for smallholder farmers, and synergetic combinations of biopesticides to enhance efficacy while minimizing environmental impacts.