The yellow stem borer (YSB), Scirpophaga incertulas, is a borer pest of low‐land rice in tropical regions of the world, reducing production and productivity. Chemical control of YSB is challenging and often less effective due to its cryptic larval feeding behaviour inside the rice culm. Biological suppression of YSB, using egg parasitoid, Trichogramma japonicum, has been well demonstrated. Kairomones, that are interspecific, play a vital role in deciding biocontrol efficiency of egg parasitoid against lepidopteran pests. However, the mechanisms involved in terms of emission of long‐ and short‐chain volatile chemicals from YSB and its by‐products and YSB damaged rice plants in attraction to T. japonicum to locate eggs of YSB are still poorly understood. In order to trace out the volatile compounds responsible for attraction of egg parasitoid, the hexane extract of YSB female whole body and acetone extract of YSB damaged rice culm were subject to GC‐MS analyses. Out of 20 chemicals, four chemicals belonging to carboxyl, alkane and saturated fatty acid [n‐hexadecanoic acid (palmitic acid), tetradecane, octadecane, n‐octadecanoic acid (stearic acid)] from female YSB hexane extract and three sesquiterpenoids (β pinene, α pinene and caryophyllene) from YSB damaged rice plant extracts were detected in greater concentrations. In laboratory assays with the synthetic form of seven chemicals, three, n‐hexadecanoic acid, n‐octadecanoic acid and octadecane, were promising in enhancing the parasitic activity of T. japonicum on YSB eggs from 26.4% to 92.6% at 200 ppm, 27.3% to 96.5% at 500 ppm and 23.6% to 82.8% at 500 ppm, respectively, in contrast to untreated eggs (87.3% at 7th day after exposure) and hexane washed eggs (16.7% at 7th day after exposure). Evaluation of these compounds revealed the key chemical cues of biocontrol potential (n‐hexadecanoic acid, n‐octadecanoic acid and octadecane) for enhancing egg parasitism activity of T. japonicum on YSB eggs.

中文翻译：

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Kairomones 对 Trichogramma japonicum 对水稻黄螟、Scirpophaga incertulas 寄生活性的影响

黄螟（YSB），Scirpophaga incertulas，是世界热带地区低地水稻的一种蛀虫，降低产量和生产力。YSB 的化学控制具有挑战性，并且由于其在稻秆内的隐秘幼虫摄食行为，通常效果较差。已经很好地证明了使用卵寄生物 Trichogramma japonicum 对 YSB 的生物抑制。Kairomones 是种间的，在决定卵寄生物对鳞翅目害虫的生物防治效率方面起着至关重要的作用。然而，从 YSB 及其副产品中释放长链和短链挥发性化学物质以及 YSB 破坏水稻植物以吸引 T. japonicum 以定位 YSB 卵的机制仍然知之甚少。为了找出引起卵寄生物吸引力的挥发性化合物，对 YSB 雌性全身的己烷提取物和 YSB 受损稻秆的丙酮提取物进行 GC-MS 分析。在 20 种化学物质中，四种化学物质属于羧基、烷烃和饱和脂肪酸 [正十六烷酸（棕榈酸）、十四烷、十八烷、正十八烷酸（硬脂酸）] 来自雌性 YSB 己烷提取物和三种倍半萜类化合物（β蒎烯） 、α蒎烯和石竹烯）从 YSB 受损的水稻植物提取物中检测到的浓度更高。在实验室检测中，使用合成形式的七种化学物质，三种，正十六烷酸、正十八烷酸和十八烷，有望将 T. japonicum 对 YSB 卵的寄生活性从 26.4% 提高到 92.6%，浓度为 27.3 ppm与未经处理的鸡蛋相比，在 500 ppm 时分别为 % 至 96.5% 和在 500 ppm 时为 23.6% 至 82.8% (87. 3%（暴露后第 7 天）和己烷清洗鸡蛋（暴露后第 7 天为 16.7%）。对这些化合物的评估揭示了生物防治潜力（正十六烷酸、正十八烷酸和十八烷）的关键化学线索，可增强 T. japonicum 对 YSB 卵的卵寄生活性。