Main Research Findings

This study evaluated the side effects of five insecticides with different modes of action (fipronil, imidacloprid, natural pyrethrins + piperonyl butoxide, pymetrozine, and triflumuron) on the protected stages of the endoparasitoid *Hyposoter didymator* at the maximum field recommended rate in Spain. *Hyposoter didymator* is a koinobiont endoparasitoid that emerges from the parasitization of economically important noctuid pests, and is considered one of the most important native biocontrol agents of noctuids in Spain. The study exposed parasitized larvae to insecticides by topical treatment or ingestion of treated artificial diet, and also treated parasitoid cocoons topically. The researchers determined host mortality and the parasitoid's subsequent development, including cocoon spinning, adult emergence, hosts attacked, and progeny production.

Reasons for Side Effects

The side effects of insecticides can vary depending on the mode of action of the insecticide, the life stage of the parasitoid, and the method of insecticide exposure.

General Side Effects

Host Mortality

The study found that insecticide treatment resulted in increased host mortality. Fipronil was consistently highly toxic regardless of exposure route. Imidacloprid killed all host insects when ingested, but was less toxic to both host and parasitoids when applied topically. 1

Parasitoid Survival

Fipronil had the strongest negative impact on parasitoid survival. It negatively affected cocoon spinning, adult emergence, hosts attacked, and progeny production. 1

Side Effect Mitigation

Parasitoid Protection

Parasitoid cocoons provided effective protection against all insecticides except fipronil. This is likely due to the cocoon's ability to prevent insecticide penetration. 1

Comparison Between Studies

Similarities

The studies demonstrated that all insecticides had some impact on the protected stages of *Hyposoter didymator*.

Differences

Different insecticides had different effects on host mortality, parasitoid survival, and susceptibility to insecticides. For example, fipronil was the most toxic insecticide, with the strongest negative impact on parasitoid survival. On the other hand, pymetrozine was harmless to *Hyposoter didymator*.

Implications for Real-World Applications

This research highlights the need to consider insecticide use and parasitoid protection in biocontrol programs. It is essential to be cautious when using highly toxic insecticides, such as fipronil, as they can have a significant negative impact on parasitoids. Choosing insecticides that are non-toxic to parasitoids, such as pymetrozine, can improve biocontrol effectiveness.

Limitations of Current Research

The study focused on *Hyposoter didymator* and *Spodoptera littoralis*. Other parasitoid and host species may have different sensitivities to insecticides. The study evaluated insecticide use at the maximum recommended field rate. In practice, lower concentrations of insecticides may be used, potentially leading to different impacts on parasitoids.

Future Research Directions

Future research should evaluate the impact of insecticides on other parasitoid and host species. It's also crucial to investigate how insecticide concentration affects parasitoid impact. Additionally, developing methods to protect parasitoids can improve the effectiveness of biocontrol programs.

Conclusion

This study evaluated the side effects of five different insecticides on the protected stages of *Hyposoter didymator*. Fipronil was the most toxic insecticide, negatively impacting parasitoid survival. Pymetrozine was non-toxic to *Hyposoter didymator*. This research highlights the importance of carefully considering insecticide use in biocontrol programs.