Evaluation of different insecticides against Liriomyza sativae (Diptera: Agromyzidae) on cucumber plants

Liriomyza sativae (Diptera: Agromyzidae) is a cosmopolitan, polyphagous pest of horticultural crops and many are resistant to insecticides. Cucumber producers in the Katahari, Biratnagar in the Eastern region of Nepal, have been facing severe challenges in recent years due to infestations by the leafminer. This pest has emerged as a major concern for local cucumber farmers, adversely affecting plant health, yield, and economic viability. The objective of this study is to investigate the efficacy of various insecticides for controlling Liriomyza and the impact of these treatments on the growth, yield, and economic aspects of cucumber cultivation. Research plots were sprayed with profenophos + cypermethrin, emamectin, chlorantraniliprole, Btk + S. spinosa, spinetoram, azadirachtin, and a water spray control. Insecticide efficacy was monitored by examining the collected leaf samples for leafminer stings, larval mines, larvae number, and rate of injury. Chlorantraniliprole and spinetoram significantly reduced the number of leafminer stings, larval mines, and the average number of larvae, resulting in lower injury rates compared to the water spray control. The insecticide treatments exhibited varying effects on plant height, number of leaves per plant, male and female flower counts, and the sex ratio. Likewise, chlorantraniliprole application led to the highest fruit number per plant, resulting in the highest yield. Other treatments also influenced these parameters but to a lesser extent. The economic analysis revealed that chlorantraniliprole had the highest total cost of cultivation but also generated the highest gross return, net return, and benefit-cost ratio. Overall, this study demonstrates that chlorantraniliprole exhibited the most promising results in terms of pest control, plant growth, yield parameters, and economic returns. These findings provide valuable insights for cucumber farmers and can aid in developing effective strategies for managing cucumber leafminers.