Target Activity of <i>Isaria tenuipes</i> (Hypocreales: Clavicipitaceae) Fungal Strains against Dengue Vector <i>Aedes aegypti</i> (Linn.) and Its Non-Target Activity Against Aquatic Predators

• Main Authors: Sengodan Karthi, Prabhakaran Vasantha-Srinivasan, Raja Ganesan, Venkatachalam Ramasamy, Sengottayan Senthil-Nathan, Hanem F. Khater, Narayanaswamy Radhakrishnan, Kesavan Amala, Tae-Jin Kim, Mohamed A. El-Sheikh, Patcharin Krutmuang
• Format: Article
• Language: English
• Published: MDPI AG 2020-09-01
• Series: Journal of Fungi
• Subjects: mycotoxins; entomopathogen; arthropods; CYP450; gut-histology; non-toxicity
• Online Access: https://www.mdpi.com/2309-608X/6/4/196

The present investigation aimed to determine the fungal toxicity of <i>Isaria tenuipes</i> (My-It) against the dengue mosquito vector <i>Aedes aegypti</i> L. and its non-target impact against the aquatic predator <i>Toxorhynchites</i><i>splendens</i>. Lethal concentrations (LC₅₀ and LC₉₀) of My-It were observed in 2.27 and 2.93 log ppm dosages, respectively. The sub-lethal dosage (My-It-1 × 10⁴ conidia/mL) displayed a significant oviposition deterrence index and also blocked the fecundity rate of dengue mosquitos in a dose-dependent manner. The level of major detoxifying enzymes, such as carboxylesterase (α-and β-) and SOD, significantly declined in both third and fourth instar larvae at the maximum dosage of My-It 1 × 10⁵ conidia/mL. However, the level of glutathione S-transferase (GST) and cytochrome P-450 (CYP450) declined steadily when the sub-lethal dosage was increased and attained maximum reduction in the enzyme level at the dosage of My-It (1 × 10⁵ conidia/mL). Correspondingly, the gut-histology and photomicrography results made evident that My-It (1 × 10⁵ conidia/mL) heavily damaged the internal gut cells and external physiology of the dengue larvae compared to the control. Moreover, the non-target toxicity against the beneficial predator revealed that My-It at the maximum dosage (1 × 10²⁰ conidia/mL) was found to be less toxic with <45% larval toxicity against <i>Tx.</i><i>splendens</i>. Thus, the present toxicological research on <i>Isaria tenuipes</i> showed that it is target-specific and a potential agent for managing medically threatening arthropods.