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Showing 2 results for Farshbaf Pour Abad
Volume 0, Issue 0 (ARTICLES IN PRESS 2024)
Abstract
Entomopathogenic fungi, Beauveria bassiana and Metarhizium anisopliae are important and effective biocontrol agents against arthropod pests. Compared to chemical insecticides, insect pests do not easily develop resistance against these fungi. In this study, the mortality and phenol-oxidase activity of the Helicoverpa armigera 3rd instar larvae were evaluated after exposure to the B. bassiana and M. anisopliae. The LC50 values for B. bassiana and M. anisopliae were 0.795 ×106, and 5.972 ×107 spore ml-1, respectively. LC30 and LC10 of either entomopathogenic fungi were injected into body of larves, then, 24 and 48 hours after injection, their hemolymph was extracted. After 24 h the highest and lowest phenol-oxidase activity was observed in LC30 of M. anisopliae, and LC10 of B. bassiana, respectively. After 48 h of infection, phenol-oxidase activity increased in all treatments. At the LC30 of M. anisopliae, the highest phenol-oxidase activity was recorded, and other treatments also showed a significant difference compared to the control. Five types of hemocytes including prohemocytes, plasmatocytes, granulocytes, onocytoids, and spherulocytes were identified in the hemolymph of larvae. The highest total hemocytes count (THC) was recorded in LC30 M. anisopliae at 9 h after initial infection. Our results showed that both fungi have the ability to affect phenol-oxidase enzyme activity. These microbial insecticides exhibited high potential for controlling the pest.
Volume 12, Issue 2 (9-2023)
Abstract
The cotton bollworm, Helicoverpa armigera (Hübner), is one of the most important pests of crops. Like other insects, this insect has an immune system against external threats such as various diseases, parasitoids, and chemical compounds. Phenoloxidase is a key factor in the immunity of insects and other arthropods. The present study investigated the lethal effects of four insecticides, indoxacarb, profenofos, chlorfluazuron, and hexaflumuron, and their effects on phenolic oxidase activity in cotton bollworm. Among the studied insecticides, in two bioassays (mixture of insecticide with artificial food and immersion of sugar beet leaves), Chlorfluazuron had the highest toxicity (LC50 = 1.71 and 3.11 mg ai/liter, respectively). Also, the highest phenol-oxidase activity at 24 h was for larvae treated with chlorfluazuron and hexaflumuron. Also, when treated with chlorfluazuron and hexaflumuron, the larvae fed on an artificial diet had higher phenoloxidase activity than those fed on sugar beet cultivars.
