Response of Cotton jassids to four different insecticides under field condition

Cotton jassid, a key sucking insect pest, has recently become one of the most damaging threats to cotton production in Tanzania, leading to significant yield losses ranging between 30% and 60% when not effectively managed. In response to this growing concern, a field study was conducted during the 2024–2025 growing season at three locations: Misungwi and Bunda in the Western Cotton Growing Area (WCGA), and Kilosa in the Eastern Cotton Growing Area (ECGA). The objective was to evaluate the efficacy of four synthetic insecticides with active ingredient Lambda-cyhalothrin, Chlorpyrifos, Imidacloprid, and Profenofos in controlling jassid populations in cotton fields. The experiment was laid out in a Randomized Complete Block Design (RCBD) with three replications. Insecticides were applied using knapsack sprayers once jassid populations reached the economic threshold level (ETL = 1-2 jassid per plant), at spray intervals of 10 to 14 days. Each treatment was replicated three times across the study sites. Jassid populations were recorded before spraying and at 24, 48 and 72 hours post-application. Population reduction percentages were calculated using Abbott’s formula, and data were analyzed using ANOVA to assess the significance of treatment differences. Results showed that all four insecticides significantly reduced jassid populations compared to the untreated control. Imidacloprid was the most effective insecticide across all sites, followed by Profenofos. For nymphs, Imidacloprid achieved mean reduction rates of 66.95%, 67.89%, and 59.53% at Kilosa, Bunda, and Misungwi, respectively, while Profenofos achieved 57.42%, 52.32%, and 52.79%. For adult jassid, Imidacloprid showed reductions of 66.15%, 60.09%, and 67.86%, while Profenofos achieved 52.31%, 47.00%, and 58.84% at the respective sites. The study concludes that Imidacloprid, when applied at the recommended dosage, offers the most effective and consistent control of cotton jassid and is strongly recommended for inclusion in Integrated Pest Management (IPM) strategies in Tanzanian cotton farming systems

棉叶蝉（Cotton jassid）是一类重要的刺吸式害虫，近年来已成为坦桑尼亚棉花生产最具破坏性的威胁之一；若未进行有效防控，将造成30%至60%的显著产量损失。针对这一日益严峻的问题，研究团队于2024–2025生长季在三个试点开展田间试验：西部棉区（Western Cotton Growing Area, WCGA）的米松圭（Misungwi）与本达（Bunda），以及东部棉区（Eastern Cotton Growing Area, ECGA）的基洛萨（Kilosa）。本试验旨在评估四种有效成分分别为高效氯氟氰菊酯（Lambda-cyhalothrin）、毒死蜱（Chlorpyrifos）、吡虫啉（Imidacloprid）与丙溴磷（Profenofos）的合成杀虫剂对棉田叶蝉种群的防控效果。实验采用完全随机区组设计（Randomized Complete Block Design, RCBD），设置三次重复。当叶蝉种群达到经济阈值（Economic Threshold Level, ETL=每株1-2头叶蝉）时，使用背负式喷雾器喷施杀虫剂，喷施间隔为10至14天，各处理在所有试点均重复三次。分别于施药前、施药后24、48、72小时记录叶蝉种群数量。采用阿伯特公式（Abbott’s formula）计算种群减退率，并通过方差分析（ANOVA）评估处理间差异的显著性。结果显示，相较于未处理的对照组，四种杀虫剂均能显著降低叶蝉种群数量。其中吡虫啉在所有试点中防控效果最优，其次为丙溴磷。针对若虫阶段，吡虫啉在基洛萨、本达、米松圭的平均减退率分别为66.95%、67.89%与59.53%；丙溴磷对应试点的减退率则为57.42%、52.32%与52.79%。对于棉叶蝉成虫，吡虫啉在上述试点的种群减退率分别为66.15%、60.09%与67.86%；丙溴磷对应数值为52.31%、47.00%与58.84%。本研究表明，按推荐剂量施用吡虫啉，可实现对棉叶蝉最有效且稳定的防控，因此强烈推荐将其纳入坦桑尼亚棉花种植体系的害虫综合防治（Integrated Pest Management, IPM）策略中。