The pathogenicity of Beauveria bassiana IRAN 441C on onion thrips and its compatibility with Flonicamid and Thiocyclam insecticides in laboratory conditions

Onion thrips is one of the most important pests of onion fields around the world, which reduces plant production. It is necessary to apply alternative strategies and reduce the concentration of chemical insecticides along with biological agents in order to prevent environmental pollution and insect resistance. Therefore, the objectives of this study were to evaluate the toxicity of Flonicamid and Thiocyclam, the virulence of entomopathogenic fungus Beauveria bassiana, and the efficiency of mixing fungus with insecticides on the 2nd instars of onion thrips and the biological factors of the pathogenic fungus. This study was performed as a completely randomized design with four replications under laboratory conditions. Insects in the control group were treated with distilled water. The results showed that LC50 values for Flonicamid, Thiocyclam and B. bassiana were 2.3 mgL-1, 4.3 mgL-1, and 5.4×107 spores mL-1, respectively. With increasing the concentration of insecticides and pathogenic fungus and also with increasing their application time, the mortality rate of onion thrips increased. Flonicamid had no effect on the germination and mycelium growth of the pathogenic fungus and was selected as a compatible insecticide. The results of mixing the pathogenic fungus with the studied insecticides showed that the studied pathogen at the concentration of 6×107 spore mL-1 along with Flonicamid at the concentration of 1.2 mgL-1 is the best combination to deal with onion thrips. Therefore, the above mixture can be recommended as an alternative for chemical insecticides after field studies in integrated management programs of onion thrips.