Location: Fruit and Tree Nut ResearchTitle: The effect of chemical insecticides on the scavenging performance of Steinernema carpocapsae: Direct effects and exposure to insects killed by chemical insecticides
|NALINCI, ELSA - Adnan Mederes University|
|KARAGOZ, MEHMET - Adnan Mederes University|
|ULUG, DERYA - Adnan Mederes University|
|GULSEN, SEBNEM HAZAL - Adnan Mederes University|
|CIMEN, HARUN - Adnan Mederes University|
|TOURAY, MUSTAPHA - Adnan Mederes University|
|Shapiro Ilan, David|
|HAZIR, SELCUK - Adnan Mederes University|
Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2021
Publication Date: 6/30/2021
Citation: Nalinci, E., Karagoz, M., Ulug, D., Gulsen, S., Cimen, H., Touray, M., Shapiro Ilan, D.I., Hazir, S. 2021. The effect of chemical insecticides on the scavenging performance of Steinernema carpocapsae: Direct effects and exposure to insects killed by chemical insecticides. Journal of Invertebrate Pathology. 184/107641. https://doi.org/10.1016/j.jip.2021.107641.
Interpretive Summary: Nematodes are simple round worms. Entomopathogenic nematodes, also called beneficial nematodes, kill insect pests; they are environmentally-friendly bioinsecticides. These nematodes mostly attack live insects but they can also enter dead insects and reproduce inside them; when they go into dead insects they are considered to be scavengers. Chemical insecticides also kill insect pests but they can they can also harm humans and the environment. It is important to see how natural pesticides, like beneficial nematodes, and chemical insecticides interact and if they are compatible for simultaneous use. We investigated the effects of three common chemical insecticides on the survival, virulence (killing power) and fitness of beneficial nematodes. We explored direct effects on the nematodes as well as the impact of chemical insecticide-killed insects on scavenger nematodes. When the chemical insecticides were mixed directly with the nematodes none of the chemicals killed the nematodes, but one of the three chemicals reduced the nematode's virulence. There was no negative effects on scavenger nematodes when they infected insecticide-killed insects. Overall our results indicate that the chemical insecticides test are generally compatible with beneficial nematodes (both in pathogenic and scavenger modes).
Technical Abstract: Entomopathogenic nematodes are used widely in biological insect control. Entomopathogenic nematodes can infect live insects as well as dead insects (i.e., they can act as scavengers). It is important to determine compatibility of entomopathogenic nematodes with other pest management tactics such as chemical insecticides. In this study, we studied the impact of chemical insecticides on scavenger nematodes. As a baseline, we first investigated the effects of direct exposure of Steinernema carpocapsae infectivity juveniles (IJs) to three chemical insecticides, cypermethrin, spinosad or diflubenzuron in terms of nematode survival and virulence. Subsequently, using the same chemicals, we tested the effects of insecticide-killed insects on scavenger nematode penetration efficiency, time of emergence and the number of IJs progeny. Prior to our study, the impact of pesticides- on scavenger nematode fitness had not been studied. Fall webworm, Hyphantria cunea, and greater wax moth, Galleria mellonella, larvae were used as host insects. The survival rate of IJs after direct exposure was 83% for cypermethrin and 93-97% for the other insecticides and control. There were no significant differences in the survival and virulence of the nematodes after 24 h exposure to insecticides. The number of nematodes that invaded the insecticide-killed host was significantly higher in cypermethrin and spinosad treated groups and live H. cunea than in the diflubenzoron treated group and freeze-killed control. However, no significant differences were observed in time of emergence. Significantly more progeny IJs emerged from Spinosad-killed insetsthan the freeze-killed control. In conclusion, we discovered that the fitness of scavenging IJs is not diminished by insecticides in insect cadavers. In fact, in some cases the exposure to chemical insecticides may enhance infectivity.