Tarbiat Modares University Journal of Agricultural Science and Technology 1680-7073 27 4 2025 07 01 Phenol-Oxidase Activity and Haemocytes Changes in Helicoverpa armigera Hübner Infected by Entomopathogenic Fungi, Beauveria bassiana and Metarhizium anisopliae 895 908 17057 10.22034/JAST.27.4.895 EN Akram Hatami Department of Plant Protection, Faculty of Agriculture, University of Tabriz, Tabriz, Islamic Republic of Iran. Reza Farshbaf Pour Abad Department of Plant Protection, Faculty of Agriculture, University of Tabriz, Tabriz, Islamic Republic of Iran. Moosa Saber Department of Plant Protection, Faculty of Agriculture, University of Tabriz, Tabriz, Islamic Republic of Iran. 0000-0001-5629-7171 Rouhollah Motafakkerazad Department of Plant Sciences, Faculty of Natural Sciences, University of Tabriz, Tabriz, Islamic Republic of Iran. Journal Article 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 lethal effects of exposure to B. bassiana and M. anisopliae, effects on phenol-oxidase activity, total haemocyte count, and changes in granulocytes and plasmatocytes were evaluated in 3^rd instar larvae of Helicoverpa armigera. The LC₅₀ values for B. bassiana and M. anisopliae were 0.795×10⁶, and 5.972×10⁷ spore mL^-1, respectively. LC₃₀and LC₁₀ of either entomopathogenic fungi were injected into the body of larvae, and 24 and 48 hours after injection, their hemolymph was extracted. After 24 hours, the highest and lowest phenol-oxidase activity was observed in LC₃₀ of M. anisopliae, and LC₁₀of B. bassiana, respectively. After 48 hours 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, oenocytoids, and spherulocytes were identified in the hemolymph of larvae. The highest Total Hemocyte Count (THC) was recorded in LC₃₀ M. anisopliae at 9 hours after initial infection. The highest number of granulocytes and plasmatocytes were recorded 9 hours after treatment in LC₃₀ of M. anisopliae and LC₃₀of B. bassiana. Our results showed that both fungi had the ability to affect phenol-oxidase enzyme activity and haemocytes. These microbial insecticides exhibited high potential for controlling the pest.<br><br> https://jast.modares.ac.ir/article_17057_ea091ca6d4f474a765f3777597b384f8.pdf