Efficacy of Thai isolates of the entomopathogenic fungus, Beauveria bassiana, and their combination with indigenous entomopathogenic nematodes against fall armyworm (Spodoptera frugiperda)

บทคัดย่อ

Fall armyworm (FAW) (Spodoptera frugiperda) is a polyphagous insect pest and is reported as one of the most destructive insect pests. Since the time FAW infestation was reported in Thailand, it has caused economic losses. Using synthetic chemicals and insecticides to control this pest may cause undesired consequences. Hence, we tested the effectiveness of entomopathogenic fungus (EPF) Beauveria bassiana isolates TBRC 2781 and TBRC 4755 against FAW individually and in combination with an indigenous entomopathogenic nematode (EPN) Heterorhabditis indica AUT 13.2 under greenhouse conditions. The second and fifth instar larvae were tested against the two isolates B. bassiana (TBRC 2781 and TBRC 4755) at different dosages of fungal spores (1x10⁵, 1x10⁶, 1x10⁷, 1x10⁸, and 1x10⁹ spores/ml). In the laboratory test, the highest mortality of second instar larvae were 72% and 63% at 1x10⁸ spores/ml for the isolates TBRC 2781 and TBRC 4755 respectively. Similarly, the highest mortality of fifth instar larvae was 34% and 24% at 1x10⁹ spores/ml for both the isolates. In the greenhouse second instar larvae were exposed to three concentrations of the fungal suspension i.e., 1x10⁸, 1x10⁹, and 1x10¹⁰ spores/ml. The highest mortality of 35% and 32% were obtained at 1x10¹⁰ spores/ml for both the isolates. In the experiment where we combined EPFs and EPNs, the mortality was increased to 55% and 40%.