Biological control potential of local entomopathogenic nematodes against the different stage larvae of cotton leafworm Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae)

Background The cotton leafworm, Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae), is an economic pest on various crops worldwide. Farmers generally used to apply chemical pesticides to control the pest. The bio-control potential of the entomopathogenic nematodes (EPNs) as alternatives to harmful synthetic pesticides was examined in this study. The study aimed to determine the efficacy of EPNs isolates against the different stages of larvae of the cotton leafworm S. littoralis and the effect of time on mortality rate under laboratory conditions. Results EPNs isolates were tested at 4 different concentrations (0, 250, 500 and 1000 IJs/ml) in 150 ml plastic containers on last instar larvae (sixth instar) of S. litorallis. Experiments for third, fourth and fifth instar larvae of S. litorallis were carried out in petri dishes at different concentrations (0, 50, 100 and 200 IJs/ml) at 25 degrees C temperature. Mortality rates of larvae were calculated at 3 different times (48, 72, 96 h) after inoculation. The high mortality rate of last instar larvae (98.81%) of S. littoralis was caused by Steinernema feltiae (Tokat-Emir), followed by S. carpocapsae (Tokat-Bakisli05) (95.24%) and then H. bacteriophora (11 KG) with (90.47%) at the highest concentration (1000 IJ/ml). The highest mortality rate of fifth instar larvae was caused by S. feltiae (Tokat-Bakisli05) and S. carpocapsae (Tokat-Emir) with (100%) and (92.12%). In addition, the highest mortality rate of the 4th instar larvae was determined S. feltiae (Tokat-Bakisli05) and S. carpocapsae (Tokat-Emir) isolates (98.87%) and (97.74%), respectively. Additionally, the highest larval mortality rate in the third stage by S. feltiae (Tokat-Bakisli05) and S. carpocapsae (Tokat-Emir) was (100%) and (97.74%) at the highest concentration. Mortality rates of larvae were calculated at 3 different times after inoculation. The highest mortality rate counted in all isolates was determined 96 and 72 h after inoculation of EPNs. Conclusions All indigenous EPN isolates were found to be effective at different rates against S. littoralis. The results showed that these nematode species could be used against S. littoralis biological control programs.