Effects of fertigation on the occurence and damages of Mahanarva fimbriolata (Stål) (Hemiptera: Cercopidae) in sugarcane

Brazil stands out as the world's largest producer of sugarcane and its productivity is closely related to the availability of water and nitrogen during its development and also to the incidence of pest insects. Among the species most harmful to the sugarcane in Brazil, Mahanarva fimbriolata stands out, which has seriously endangered the yields. In this context, the present study aimed to evaluate the effect of the nitrogen fertirrigation on the incidence and damage caused by M. fimbriolata in sugarcane. The experiment was composed of five treatments and four replications in a randomized block design (RBD). The treatments were composed of four doses of N-fertilizer and control (0, 50, 100, 150, 200 kg.ha-1) in drip irrigation system. The parameters evaluated were: number of nymphs in the roots, stalk productivity, sugar content, percentage of sugar, total recoverable sugar and the agricultural contribution margin. It was observed that the fertirrigation increases the productivity of stalks and sugar with the increase of nitrogen fertilization by irrigation. The use of 200 kg.ha-1 of N-fertilizer increased the incidence of M. fimbriolata up to the control and economic damage levels. The biggest financial yield was obtained with the dose of 150 kg.ha-1 of N-fertilizer.

巴西为全球最大的甘蔗生产国，其甘蔗生产力与生长发育期的水分、氮素供应及害虫发生情况密切相关。在巴西危害甘蔗的主要害虫物种中，蔗黄象蜡蝉（Mahanarva fimbriolata）尤为突出，该物种已严重威胁甘蔗产量。在此背景下，本研究旨在评估滴灌施氮对蔗黄象蜡蝉（Mahanarva fimbriolata）在甘蔗上的发生程度与为害损失的影响。试验采用随机区组设计（randomized block design, RBD），设置5个处理、4次重复。处理组包含4个氮肥施用剂量与1个对照组，剂量分别为0、50、100、150、200 kg·ha⁻¹，采用滴灌系统实施施肥灌溉。本试验测定的指标包括：根部若虫数量、茎秆产量、蔗糖含量、糖分百分比、总可回收糖量及农业贡献边际。研究结果表明，随灌溉施氮量增加，滴灌可提升茎秆与蔗糖产量。施用200 kg·ha⁻¹氮肥时，蔗黄象蜡蝉（M. fimbriolata）的发生量升至对照水平及经济为害阈值。而150 kg·ha⁻¹的氮肥剂量可获得最高经济效益。