Multigenerational Insecticide Hormesis Enhances Fitness Traits in a Key Egg Parasitoid, <i>Trichogramma chilonis</i> Ishii

• Published in: Agronomy
• Main Authors: Aishwarya Ray, Basana-Gowda Gadratagi, Dhanendra Kumar Rana, Farman Ullah, Totan Adak, Guru-Pirasanna-Pandi Govindharaj, Naveenkumar B Patil, Annamalai Mahendiran, Nicolas Desneux, Prakash Chandra Rath
• Format: Article
• Language: English
• Published: MDPI AG 2022-06-01
• Subjects: biological control; demographic parameters; hormesis; imidacloprid; sublethal effects
• Online Access: https://www.mdpi.com/2073-4395/12/6/1392

Hormesis for the intractable pests can be dreadful, but for natural enemies of pests, it is a puissant strategy in optimizing their mass rearing. We report multigenerational stimulatory effects of widely used insecticide, imidacloprid, on the demographic traits of an important egg parasitoid <i>Trichogramma chilonis</i> Ishii. The study investigated the consequences of sublethal (LC₅), low lethal (LC₃₀), and median lethal (LC₅₀) concentrations, as well as a control, for five continuous generations (F₁ to F₅). The initial bioassay experiments revealed imidacloprid exhibiting the highest toxicity for the parasitoid with a LC₅₀ of 2 µg·L⁻¹, whereas LC₅ and LC₃₀ were 0.07 µg·L⁻¹ and 0.6 µg·L⁻¹, respectively. Among biological traits, compared to the F₁ individuals, a substantial increase in the fecundity of <i>T. chilonis</i> was observed in the F₅ individuals by 54.92% and 46.81% when exposed to LC₅ and LC₃₀, respectively (<i>p</i> < 0.00001). Further, there was a significant enhancement in the adult longevity as well as oviposition days of the F₅ individuals at both these concentrations. Considering the population traits, along with gross reproductive rate (<i>GRR</i>), net reproductive rate (<i>R</i>₀) was also enhanced by both LC₅ and LC₃₀ in F₅ individuals than F₁; whereas the intrinsic rate of increase (<i>r</i>) and finite rate of increase (<i>λ</i>) were enhanced only at LC₃₀ upon comparing with control. On the other hand, LC₅₀ exposure to <i>T. chilonis</i> did not result in notable differences in biological or population traits when compared across generations (F₁ and F₅). Low and sublethal concentrations of imidacloprid did not have a major influence on demographic traits of <i>T</i>. <i>chilonis</i> at initial generations of exposure but can induce hormetic effects in the subsequent generations. Overall, imidacloprid-induced hormesis stimulating the development of <i>T</i>. <i>chilonis</i> might be helpful under circumstances of mild exposure of imidacloprid in fields and could be leveraged for its mass rearing.