Abstract The red palm weevil (RPW) Rhynchophorus ferrugineus Olivier is the most devastating pest of date palm, with a severe impact on cultivation and production. The virulence of five species/strains of entomopathogenic nematodes (EPNs), Steinernema scapterisci (Ss), Steinernema sp. (SII), Steinernema abbasi (Ab), Steinernema glaseri (Sg), and Heterorhabditis bacteriophora (HP88) was tested against larval and adult stages of RPW under semi-field laboratory conditions. Total and differential haemocyte counts were determined, and protein analysis and histopathological study of larvae injected with SII and HP88 were performed. Susceptibility results revealed that the larval stage was much more susceptible to Sg and HP88 than the adult stage. Larval mortality rate was as high as 100% and 92%, respectively, with concentrations of 1250 infective juveniles (IJs)/pot, while adult mortality reached 48% and 60%, respectively, with concentrations of 20 000 IJs/pot at 9 d post infection with Sg and HP88. In general, SS, SII, and Ab appeared to be more virulent during the adult stage than the larval stage. They recorded mortality rates of 88%, 88%, and 72%, respectively, for the larval stage, and 100%, 100%, and 84%, respectively, for the adult stage at concentrations of 20 000 IJs/pot at 9 d post infection. A severe decline in the total and differential haemocyte counts (THCs and DHCs) at 12 h post-injection with SII and HP88 at 20 IJs/larvae was observed. Similarly, the effect on total haemolymph protein of the normal and infected larvae was reflected by the appearance and disappearance of protein bands in addition to changes in the protein band concentration. Notably, remarkable changes in the cuticle, in the form of disruption to the outer epicuticle, splitting of the epidermal layer, and disorganization of the musculature region, were observed. In addition, notable histological effects were seen in the midgut region at 12 h post injection with 20 IJs/larvae of HP88 and SII. Our results demonstrate that R. ferrugineus is unable to defend itself against EPNs. These results indicate an effective and natural biological control strategy with potential for application as an eco-friendly and inexpensive insecticide against the adult and larval stages of the RPW.

中文翻译：

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Rhynchophorus ferrugineus (Olivier) (Coleoptera: Curculionidae) 对昆虫病原线虫的免疫反应敏感性

摘要 红棕象甲(RPW) Rhynchophorus ferrugineus Olivier 是枣椰树上危害最大的害虫，对栽培和生产造成严重影响。五种昆虫病原线虫 (EPNs)、Steinernema scapterisci (Ss)、Steinernema sp. 的毒力。(SII)、Steinernema abbasi (Ab)、Steinernema glaseri (Sg) 和 Heterorhabditis bacteriophora (HP88) 在半田间实验室条件下针对 RPW 的幼虫和成虫阶段进行了测试。测定总血细胞计数和分类血细胞计数，并对注射了 SII 和 HP88 的幼虫进行蛋白质分析和组织病理学研究。易感性结果表明，幼虫阶段比成虫阶段更容易受到 Sg 和 HP88 的影响。幼虫死亡率分别高达100%和92%，Sg 和 HP88 感染后 9 天浓度为 20 000 IJs/pot，成虫死亡率分别达到 48% 和 60%，浓度为 1250 个感染性幼鱼（IJs）/锅。一般来说，SS、SII 和 Ab 在成虫阶段似乎比幼虫阶段更具毒性。他们记录的 9 d 浓度为 20 000 IJs/pot 时，幼虫期死亡率分别为 88%、88% 和 72%，成虫期死亡率分别为 100%、100% 和 84%感染后。观察到以 20 IJ/幼虫注射 SII 和 HP88 后 12 小时，血细胞总数和分类血细胞计数（THC 和 DHC）严重下降。相似地，除了蛋白条带浓度的变化外，还通过蛋白条带的出现和消失来反映对正常和感染幼虫总血淋巴蛋白的影响。值得注意的是，观察到表皮的显着变化，表现为外表皮破裂、表皮层分裂和肌肉组织区域的紊乱。此外，在注射 20 个 IJ/幼虫的 HP88 和 SII 后 12 小时，在中肠区域观察到显着的组织学效应。我们的结果表明，R. ferrugineus 无法抵御 EPN。这些结果表明一种有效和自然的生物控制策略，具有作为一种对 RPW 成虫和幼虫阶段的生态友好且价格低廉的杀虫剂应用的潜力。观察到外表皮破裂、表皮层分裂和肌肉组织区域解体。此外，在注射 20 个 IJ/幼虫的 HP88 和 SII 后 12 小时，在中肠区域观察到显着的组织学效应。我们的结果表明，R. ferrugineus 无法抵御 EPN。这些结果表明一种有效和自然的生物控制策略，具有作为一种对 RPW 成虫和幼虫阶段的生态友好且价格低廉的杀虫剂应用的潜力。观察到外表皮破裂、表皮层分裂和肌肉组织区域解体。此外，在注射 20 个 IJ/幼虫的 HP88 和 SII 后 12 小时，在中肠区域观察到显着的组织学效应。我们的结果表明，R. ferrugineus 无法抵御 EPN。这些结果表明一种有效和自然的生物控制策略，具有作为一种对 RPW 成虫和幼虫阶段的生态友好且价格低廉的杀虫剂应用的潜力。我们的结果表明，R. ferrugineus 无法抵御 EPN。这些结果表明一种有效和自然的生物控制策略，具有作为一种对 RPW 成虫和幼虫阶段的生态友好且价格低廉的杀虫剂应用的潜力。我们的结果表明，R. ferrugineus 无法抵御 EPN。这些结果表明一种有效和自然的生物控制策略，具有作为一种对 RPW 成虫和幼虫阶段的生态友好且价格低廉的杀虫剂应用的潜力。