Target Activity of Isaria tenuipes (Hypocreales: Clavicipitaceae) Fungal Strains against Dengue Vector Aedes aegypti (Linn.) and Its Non-Target Activity Against Aquatic Predators
2020
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
The present investigation aimed to determine the fungal toxicity of Isaria tenuipes (My-It) against the dengue mosquito vector Aedes aegypti L. and its non-target impact against the aquatic predator Toxorhynchitessplendens. 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 (&alpha:-and &beta:-) 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 Tx.splendens. Thus, the present toxicological research on Isaria tenuipes showed that it is target-specific and a potential agent for managing medically threatening arthropods.
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