Microbial Bioactives

Abstract

Background: Entomopathogenic nematodes (EPNs) are obligate lethal parasites of insects and are globally used as safe biocontrol agents against a wide range of insect pests. They occur in most agricultural soils all around the world. The insecticidal activity of two native EPNs Heterorhabditis bacteriophora (BA1) and Steinernema carpocapsae (BA2), isolated from the Egyptian soil was examined against eight different economic insect pests under laboratory conditions. These pests are the Greater wax moth larvae, Galleria mellonella; the cotton leafworm, Spodoptera littorallis; the cutworm, Agrotis ipsilon; the european corn borer, Osterinia nubilalis; the greater sugarcane borer, Sesamia critica; the apple tree borer, Zeuzera pyrina; the sugar beet fly, Pegomyia mixta and the tortoise beetle Cassida vittatta. Three nematode concentrations (100, 50, and 25 /ml water) of infective juveniles (IJs) were applied per insect. The test was conducted at 25± 2 °C and about 70± 2 % RH. Results: The median lethal concentration (LC₅₀) of H. bacteriophora BA1– was almost– higher than that of S. capocapsae BA2 against the different tested insect pest larvae. The percentage of the cumulative mortality ranged between 46 and 100% in general, according to the tested concentration and/or the nematode species. The comparison between the mortality percentages caused by BA1 and BA2 nematodes to differently treated insect larvae revealed that BA1 was almost more virulent than BA2. Results showed that the lowest LC₅₀ value was found to be 2.15 IJs, for H. bacteriophora BA1 isolate. Conclusions: The results showed that both indigenous EPNs isolates had a good impact in the management of the eight economic insect pests tested in this study had insecticidal properties and could be positively enrolled in integrated pest management programs against different insect pests.

Key Words: EPNs; Biocontrol; Cutworms; Borers; Sugar beet pests