Department of Zoology, Guru Nanak Dev University, Punjab, Amritsar, 143005, India.
Department of Microbiology, Guru Nanak Dev University, Punjab, Amritsar, 143005, India.
BMC Microbiol. 2023 Apr 3;23(1):95. doi: 10.1186/s12866-023-02841-w.
Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae) also known as tobacco caterpillar, is one of the most serious polyphagous pests that cause economic losses to a variety of commercially important agricultural crops. Over the past few years, many conventional insecticides have been used to control this pest. However, the indiscriminate use of these chemicals has led to development of insecticide resistant populations of S. litura in addition to harmful effects on environment. Due to these ill effects, the emphasis is being laid on alternative eco-friendly control measures. Microbial control is one of the important components of integrated pest management. Thus, in search for novel biocontrol agents, the current work was carried out with the aim to evaluate the insecticidal potential of soil bacteria against S. litura.
Among the tested soil bacterial isolates (EN1, EN2, AA5, EN4 and R1), maximum mortality (74%) was exhibited by Pseudomonas sp. (EN4). The larval mortality rate increased in a dose-dependent manner. Bacterial infection also significantly delayed the larval development, reduced adult emergence, and induced morphological deformities in adults of S. litura. Adverse effects were also detected on various nutritional parameters. The infected larvae showed a significant decrease in relative growth and consumption rate as well as efficiency of conversion of ingested and digested food to biomass. Histopathological studies indicated damage to the midgut epithelial layer of larvae due to the consumption of bacteria treated diet. The infected larvae also showed a significantly decreased level of various digestive enzymes. Furthermore, exposure to Pseudomonas sp. also caused DNA damage in the hemocytes of S. litura larvae.
Adverse effects of Pseudomonas sp. EN4 on various biological parameters of S. litura indicate that this soil bacterial strain may be used as an effective biocontrol agent against insect pests.
斜纹夜蛾（Spodoptera litura）（鳞翅目：夜蛾科）也被称为烟青虫，是一种严重的多食性害虫，会对各种重要的商业作物造成经济损失。在过去的几年中，许多常规杀虫剂被用于防治这种害虫。然而，这些化学物质的滥用不仅导致了斜纹夜蛾对杀虫剂的抗性种群的发展，还对环境造成了有害影响。由于这些负面影响，人们越来越重视替代环保的控制措施。微生物防治是综合虫害管理的重要组成部分之一。因此，为了寻找新的生物防治剂，目前的工作旨在评估土壤细菌对斜纹夜蛾的杀虫潜力。
在所测试的土壤细菌分离株（EN1、EN2、AA5、EN4 和 R1）中，假单胞菌（EN4）表现出最高的死亡率（74%）。幼虫死亡率呈剂量依赖性增加。细菌感染还显著延迟了幼虫的发育，减少了成虫的出现，并诱导了斜纹夜蛾成虫的形态畸形。对各种营养参数也检测到了不良影响。受感染的幼虫的相对生长率、摄食率以及摄入和消化食物转化为生物量的效率均显著降低。组织病理学研究表明，由于食用了经细菌处理的饲料，幼虫的中肠上皮层受到了损伤。受感染的幼虫还表现出各种消化酶水平的显著降低。此外，暴露于假单胞菌也导致了斜纹夜蛾幼虫血细胞中的 DNA 损伤。
假单胞菌 EN4 对斜纹夜蛾的各种生物学参数的不利影响表明，这种土壤细菌菌株可作为防治昆虫的有效生物防治剂。
