The lettuce aphid, Nasonovia ribisnigri (Mosley), is recognized as one of the most destructive insect pests of lettuce in major production regions worldwide. This species causes direct damage through continuous phloem feeding, resulting in reduced plant vigor, foliar deformation, and significant deterioration of marketable quality. Chemical control remains a cornerstone of lettuce aphid management programs; however, the intensive and repeated use of insecticides with similar modes of action has raised concerns regarding resistance evolution, reduced field efficacy, and the long-term sustainability of aphid management strategies. Consequently, the identification and evaluation of insecticides with novel modes of action have become increasingly important for insecticide resistance management (IRM) programs and may also contribute to integrated pest management (IPM) strategies. . Therefore, the present study was conducted to evaluate the efficacy of dimpropyridaz (Efficon® 120 SL) compared with spirotetramat (Movento® 10% SC) and flonicamid (Teppeki® 50% WG) against N. ribisnigri in commercial lettuce fields of Golestan Province, Iran.

Materials and Methods

Field experiments were conducted during the 2025 growing season in three commercial lettuce fields located in the eastern, central, and western regions of Golestan Province, Iran. Each field was managed according to standard commercial production practices, and treatments were applied at the rosette stage when aphid populations were actively colonizing inner leaves. The experiment was arranged as a randomized complete block design (RCBD) with three replications per location. Six treatments were evaluated: dimpropyridaz (Efficon® 120 SL) at 0.50 and 0.75 mL L⁻¹, spirotetramat (Movento® 10% SC) at 0.50 and 0.75 mL L⁻¹, flonicamid (Teppeki® 50% WG) at 0.50 g L⁻¹, and an untreated control.

Aphid populations were assessed on five randomly selected plants per plot by counting the number of N. ribisnigri individuals per plant. Counts were performed before treatment application (pre-treatment baseline) and at 3, 7, and 14 days after treatment (DAT). Data were analyzed using a repeated-measures linear mixed-effects model (LMM) fitted with the function in the nlme package in R software (v4.4.1). Treatment, sampling date, and their interaction were considered fixed effects, while plot identity was included as a random factor to account for repeated measurements within experimental units. Estimated marginal means (EMMs) were calculated, and pairwise comparisons were performed using Sidak-adjusted contrasts to control the family-wise error rate. Biological efficacy was additionally calculated using the Henderson–Tilton formula.

Results

The linear mixed-effects model indicated significant effects of treatment (P < 0.05), sampling date (P < 0.05), and the treatment × sampling date interaction (P < 0.05) on N. ribisnigri density. All insecticide treatments significantly reduced aphid populations compared with the untreated control throughout the evaluation period. Aphid densities declined markedly within three days after application in all insecticide-treated plots and remained substantially suppressed until the final assessment at 14 days after treatment (DAT). Pairwise comparisons among insecticide treatments revealed no statistically significant differences, indicating comparable aphicide performance among all evaluated products and rates. Nevertheless, dimpropyridaz at 0.75 mL L⁻¹ consistently exhibited the lowest mean adjusted aphid density across all sampling dates. Henderson–Tilton efficacy calculations further showed that this treatment achieved the highest corrected efficacy (97.33 ± 1.88%) among the evaluated insecticides. The untreated control maintained significantly higher aphid densities than all insecticide-treated plots throughout the study period.

Discussion

The results demonstrate that dimpropyridaz provided effective and sustained suppression of N. ribisnigri under commercial field conditions, showing comparable performance with the established aphicides spirotetramat and flonicamid. Although no statistically significant differences in efficacy were detected among insecticide treatments, dimpropyridaz at 0.75 mL L⁻¹ showed the highest numerical efficacy across all evaluation intervals, suggesting that studies with greater statistical power may be useful to further confirm this trend. To the best of our knowledge, this study represents the first field-based evaluation of dimpropyridaz against lettuce aphid in Iran. Considering its distinct mode of action within IRAC Group 36 and the lack of reported cross-resistance with conventional aphicide classes, dimpropyridaz may provide a valuable new option for diversifying chemical control programs and supporting sustainable IRM strategies in commercial lettuce production systems.