Combined cultural and chemical tactics reduce tomato yield loss from leafminer (Phthorimaea absoluta Meyrick (Lepidoptera: Gelechiidae)) infestations in Southern Ethiopia

Tomato isglobally important vegetable crop, but its productivity is significantly threatened by the leafminer (Phthorimaea absoluta), a highly destructive pest that damages leaf and fruit. Although chemical control remains the main management tactic for leafminer, its indiscriminate use poses risks to non-target organisms. Integrated management strategy, combining cultural and chemical tactics, offers an alternative control measure with multiple advantages. Field experiments were conducted in 2020 and 2021 at Arba Minch (AM) and Mihirab Abaya (MA) in southern Ethiopia to evaluate the effectiveness of integrating cultural practices (earthing-up) with various ratios of different insecticide sprays in reducing leafminer damage, minimizing yield losses, and enhancing tomato agronomic performance. Twenty-two treatments were factorial arranged within a randomized complete block design with three replications. Results showed that three-time earthing-up combined with 50 % Spinosad and 100 % Nimbicidine significantly reduced larval populations (83.76 % and 86.99 %) and leaf-mining (75.84 % and 68.70 %) while lowering leaf damage (9.59 % and 10.07 %) and increasing marketable yield (46.96 and 48.52 t ha⁻¹) compared to untreated controls at AM and MA, respectively. This treatment also minimized yield loss by 80.75 % and 76.07 % and increased yield advantage by 419.47 % and 317.92 % at AM and MA, in that order. However, financial analysis revealed that two-time earthing-up combined with 50 % Spinosad and 50 % Nimbicidine provided the highest benefit-cost ratio (49.38 and 50.03) at AM and MA, respectively. The study concludes that integrating two-time earthing-up with 50 % Spinosad and 50 % Nimbicidine is an effective, economically viable approach for leafminer management, optimizing tomato yield while maximizing financial returns. This approach is recommended for effective leafminer management in tomato production systems.