Tullika Thokchom, Ningthoujam Kennedy
School of Crop Protection, College of Post Graduate Studies in Agricultural Sciences, CAU (I), Umiam, Meghalaya, 793103, India.
J Chem Ecol. 2024 Dec;50(12):1046-1055. doi: 10.1007/s10886-024-01534-6. Epub 2024 Aug 21.
Egg parasitoids, particularly Trichogrammatidae, play a crucial role in global biocontrol efforts. Their behavior is influenced by chemicals emitted by their hosts, such as kairomones. Among them, Trichogramma pretiosum (Riley) (Hym.; Trichogrammatidae) shows promise as a biocontrol agent on destructive Fall Armyworm (FAW), Spodoptera frugiperda (J.E. Smith) (Lep.; Noctuidae). Given the invasiveness and widespread impact of FAW, early-stage prevention in the field is imperative. This study aimed to assess the potential of host insects viz.,Corcyra cephalonica (Stainton) (Lep.; Pyralidae) and S. frugiperda kairomones in optimizing the performance of T. pretiosum while parasitizing S. frugiperda. The top two hexane extracts from each host insect were also sent to JNU, AIRF in New Delhi for detailed GC-MS analysis. A four-armed olfactometer was developed to track the movements of T. pretiosum and validated with olfactory cues. Laboratory bioassays revealed that extracts from C. cephalonica and S. frugiperda eggs and moths effectively enhanced the performance of T. pretiosum. Optimal concentrations were determined through Petri dish bioassays, with C1 (10%) concentration of C. cephalonica eggs extract showing the highest Parasitoid Activity Index (PAI), percent parasitization, and adult emergence. Meanwhile, C2 (1%) concentration of S. frugiperda female extract exhibited the highest parasitization percentage and adult emergence. Further assessments in a polyhouse setting demonstrated that treated egg cards positioned 1 m from the release point achieved the highest mean percentage parasitization. Chemical composition analysis via GC-MS revealed that distinctive hydrocarbon and alcohol profiles in the extracts, suggesting their potential for manipulating parasitoid activity in biocontrol efforts. In the S. frugiperda female extract, 12 hydrocarbons and 3 alcohol groups were identified, with tetracontane as the predominant hydrocarbon compound followed by octane, heneicosane, and others. Meanwhile, the C. cephalonica egg extract displayed 9 hydrocarbons and 1 alcohol group, with dodecane leading in area percentage among the hydrocarbons followed by decane, nonane and others. The outputs of current study highlighted that T. pretiosum's utilization of kairomones from C. cephalonica and S. frugiperda, enhancing its search behavior for host eggs. The identification and synthesis of these kairomonal compounds have the potential to revolutionize pest management, emphasizing the role of kairomones in empowering natural predators and parasitoids for sustainable agriculture.
卵寄生蜂，尤其是赤眼蜂科，在全球生物防治工作中发挥着关键作用。它们的行为受到宿主释放的化学物质影响，如利它素。其中，拟澳洲赤眼蜂（Trichogramma pretiosum (Riley) （膜翅目；赤眼蜂科））有望成为防治破坏性草地贪夜蛾（Spodoptera frugiperda (J.E. Smith) （鳞翅目；夜蛾科））的生物防治剂。鉴于草地贪夜蛾的入侵性和广泛影响，田间早期预防势在必行。本研究旨在评估宿主昆虫，即米蛾（Corcyra cephalonica (Stainton) （鳞翅目；螟蛾科））和草地贪夜蛾的利它素在优化拟澳洲赤眼蜂寄生草地贪夜蛾时的性能方面的潜力。每种宿主昆虫的前两种己烷提取物也被送往新德里的贾瓦哈拉尔·尼赫鲁大学先进仪器研究设施进行详细的气相色谱 - 质谱分析。开发了一种四臂嗅觉仪来追踪拟澳洲赤眼蜂的运动，并通过嗅觉线索进行了验证。实验室生物测定表明，米蛾和草地贪夜蛾卵及成虫的提取物有效地提高了拟澳洲赤眼蜂的性能。通过培养皿生物测定确定了最佳浓度，米蛾卵提取物的C1（10%）浓度显示出最高的寄生蜂活性指数（PAI）、寄生率和成虫羽化率。同时，草地贪夜蛾雌虫提取物的C2（1%）浓度表现出最高的寄生率和成虫羽化率。在温室环境中的进一步评估表明，放置在距释放点1米处的处理过的卵卡实现了最高的平均寄生率。通过气相色谱 - 质谱进行的化学成分分析表明，提取物中具有独特的烃类和醇类谱，表明它们在生物防治中操纵寄生蜂活性的潜力。在草地贪夜蛾雌虫提取物中，鉴定出12种烃类和3个醇类基团，其中四十烷是主要的烃类化合物，其次是辛烷、二十一烷等。同时，米蛾卵提取物显示出9种烃类和1个醇类基团，在烃类中十二烷的面积百分比领先，其次是癸烷、壬烷等。当前研究的结果突出表明，拟澳洲赤眼蜂利用米蛾和草地贪夜蛾的利它素，增强了其对宿主卵搜索行为。这些利它素化合物的鉴定和合成有可能彻底改变害虫管理，强调了利它素在增强自然捕食者和寄生蜂以实现可持续农业方面的作用。
