Effectiveness study of the dual application of new Indigenous entomopathogenic nematode isolate Heterorhabditis taysearae and entomopathogenic fungi Beauveria bassiana against armyworm (Spodoptera frugiperda)

The fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), is a polyphagous insect pest species that travel great distances every summer to disperse. They mostly feed on maize and over 350 other crops. In this investigation, two entomopathogens: Beauveria bassiana and Heterorhabditis taysearae, were utilized to test the efficacy of each against S. frugiperda separately and then as a group by inoculating H. taysearae two days after fungal infection.

Evaluations were done on mortality percentage, infective juvenile (IJ) production, and conidia production. The LT₅₀ continually reduced with increases in nematode and fungus concentrations. For the LC₅₀ value, the H. taysearae isolate was 289 IJs/larva after 96 h of treatment, while for B. bassiana isolate, it was 10⁶ CFU/ml after 144 h of treatment. Dual infections with B. bassiana and H. taysearae had a beneficial effect on pest mortality, resulting in 83% mortality, and caused a significant increase in conidia production while utilizing the nematode or fungal separately caused decrease in mortality (63 and 73%, respectively).

The study’s findings indicated a quicker time to death and suggested that combining a moderately pathogenic fungal isolate with nematodes could raise the mortality rate. The mutually beneficial relationship between B. bassiana and H. taysearae controls S. frugiperda.