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Published on: December 11, 2012
Temperature Effects on Heterorhabditis megidis and Steinernema carpocapsae Infectivity to Galleria mellonella
Abstract:
The effect of temperature on the infection of larvae of the greater wax moth, Galleria mellonella, by Heterorhabditis megidis H90 and Steinernema carpocapsae strain All, was determined. For both species, infection, reproduction, and development were fastest at 20 to 24 degrees C. Infection by both H. megidis and S. carpocapsae occurred between 8 and 16 degrees C; however, neither species reproduced at 8 degrees C. Among the nematodes used in experiments at 8 degrees C, no H. megidis and very few S. carpocapsae developed beyond the infective juvenile stage. Compared with H. megidis, S. carpocapsae invaded and killed G. mellonella larvae faster at 8 to 16 degrees C. By comparing invasion rates, differences in infectivity between the two nematode species were detected that could not be detected in conventional petri dish bioassays where mortality was measured after a specified period. Invasion of G. mellonella larvae by H. megidis was faster at 24 than at 16 degrees C.
Insights
Temperature significantly impacts entomopathogenic nematode efficacy. Both Heterorhabditis megidis and Steinernema carpocapsae showed optimal infection and reproduction between 20-24°C, with S. carpocapsae exhibiting faster invasion at lower temperatures.
Area of Science:
- Nematology
- Entomology
- Pest Management
Background:
- Entomopathogenic nematodes (EPNs) are crucial biological control agents.
- Temperature is a key environmental factor influencing EPN efficacy.
- Understanding temperature-dependent interactions is vital for optimizing EPN applications.
Purpose of the Study:
- To determine the effect of temperature on the infectivity and reproductive success of Heterorhabditis megidis and Steinernema carpocapsae.
- To compare the temperature-dependent performance of these two EPN species against Galleria mellonella.
- To evaluate if invasion rate assays reveal infectivity differences not apparent in standard bioassays.
Main Methods:
- Larvae of Galleria mellonella were exposed to Heterorhabditis megidis H90 and Steinernema carpocapsae strain All at various temperatures (8°C, 16°C, 20-24°C).
- Infection, nematode reproduction, and development were assessed.
- Larval invasion rates by EPNs were compared at different temperatures.
Main Results:
- Optimal infection, reproduction, and development for both EPN species occurred at 20-24°C.
- Infection was observed between 8-16°C, but reproduction was absent at 8°C.
- Steinernema carpocapsae invaded and killed Galleria mellonella larvae faster than Heterorhabditis megidis at 8-16°C.
- Invasion rate assays revealed infectivity differences not detected by traditional mortality assays.
Conclusions:
- Temperature critically influences the efficacy of Heterorhabditis megidis and Steinernema carpocapsae against Galleria mellonella.
- Steinernema carpocapsae demonstrates superior performance at lower temperatures (8-16°C) compared to Heterorhabditis megidis.
- Invasion rate assays provide a more sensitive measure of EPN infectivity than standard mortality bioassays.
