Demographic toxicology of insect growth regulators on the nontarget ectolarval parasitoid Habrobracon hebetor

• Published in: Scientific reports Vol. 14; no. 1; pp. 26189 - 9
• Main Authors: Mansour, Amany N., Ghoneim, Karem S., Hamadah, Khaled S., Elsoud, Ahmed A. Abo
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 31-10-2024; Nature Portfolio
• Subjects: 631/158/2456; 631/449; 631/601/1466; Animals; Female; Host-Parasite Interactions - drug effects; Humanities and Social Sciences; Hydrazines - pharmacology; Hydrazines - toxicity; Hymenoptera - drug effects; Hymenoptera - growth & development; Hymenoptera - physiology; Insecticides - toxicity; Juvenile Hormones - pharmacology; Male; Moths - drug effects; Moths - growth & development; Moths - parasitology; multidisciplinary; Phenylurea Compounds - pharmacology; Pyridines - pharmacology; Pyridines - toxicity; Science; Science (multidisciplinary); Sex Ratio; Wasps - drug effects; Wasps - growth & development; Wasps - physiology
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-024-75634-4

Habrobracon hebetor
Say (Hymenoptera: Braconidae) is one of the most important parasitoids of many pyralid moths, including the olive leaf moth,
Palpita unionalis
Hubner (Lepidoptera: Pyralidae). The widespread use of insecticides threatens natural enemies. Assessing the side effects of insecticides on nontarget organisms supports the rational use of insecticides during field application. The present study evaluates the lethal and sublethal effects of three insect growth regulators (IGRs), novaluron, methoxyfenozide, and pyriproxyfen, on
P. unionalis
and the demographic toxicology of these IGRs on its parasitoid
H. hebetor
. The LC
50
values of these IGRs on
P. unionalis
were 0.97, 0.176, and 0.00009 ppm, respectively, indicating that pyriproxyfen was the most toxic. When
H. hebetor
adults were exposed to these LC
50
levels under laboratory conditions to determine possible side effects. The IGRs did not affect the paralysis and parasitism rates of the parasitoid nor the sex ratio of its offspring. IGR treatments slightly reduced hatching rates and immature survival by 15–25%, indicating moderate effects on the early developmental stages of
H. hebetor
. The longevity and fecundity of treated females were each reduced to < 50% of their respective values in untreated females. Additionally, some demographic parameters of the parasitoid were significantly affected by the IGRs. Nevertheless, despite these observed effects, the positive net reproductive rate (R
0
 > 0) and intrinsic rate of increase (r
m
> 1) of
H. hebetor
indicated an exponential population increase that reflects the compatibility of the IGRs with the parasitoid. Our results demonstrated that the tested IGRs could be categorized as relatively harmless compounds to the parasitoid. Following these laboratory assessments, field studies will be required to confirm the effects of the tested IGRs on
H. hebetor
as well as other nontarget organisms.