Abstract
Juvenile hormone analog (JHA) insecticides are biological and structural mimics of JH, a key insect developmental hormone. Toxic and anti-developmental effects of the JHA insecticides methoprene, fenoxycarb, and pyriproxyfen were investigated on the larval and pupal stages of Spodoptera littoralis and Spodoptera frugiperda. Bioassays showed that fenoxycarb has the highest toxicity and fastest speed of kill in 2nd instar S. littoralis. All three JHAs affected the development of 6th instar (i.e., final instar) and pupal S. frugiperda. JH esterase (JHE) is a critical enzyme that helps to regulate JH levels during insect development. JHE activity in the last instar S. littoralis and S. frugiperda was 11 and 23 nmol min-1 ml-1 hemolymph, respectively. Methoprene and pyriproxyfen showed poor inhibition of JHE activity from these insects, whereas fenoxycarb showed stronger inhibition. The inhibitory activity of fenoxycarb, however, was more than 1000-fold lower than that of OTFP, a highly potent inhibitor of JHEs. Surprisingly, topical application of methoprene, fenoxycarb or pyriproxyfen on 6th instars of S. littoralis and S. frugiperda prevented the dramatic reduction in JHE activity that was found in control insects. Our findings suggest that JHAs may function as JH agonists that play a disruptive role or a hormonal replacement role in S. littoralis and S. frugiperda.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 30-36 |
| Number of pages | 7 |
| Journal | Pesticide Biochemistry and Physiology |
| Volume | 128 |
| DOIs | |
| State | Published - Mar 1 2016 |
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Keywords
- Inhibition
- JH esterase
- Juvenile hormone (JH) analog insecticide
- S. frugiperda
- Spodoptera littoralis
ASJC Scopus subject areas
- Agronomy and Crop Science
- Health, Toxicology and Mutagenesis
Cite this
Effects of juvenile hormone (JH) analog insecticides on larval development and JH esterase activity in two spodopterans. / El-Sheikh, El Sayed A; Kamita, Shizuo G.; Hammock, Bruce D.
In: Pesticide Biochemistry and Physiology, Vol. 128, 01.03.2016, p. 30-36.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Effects of juvenile hormone (JH) analog insecticides on larval development and JH esterase activity in two spodopterans
AU - El-Sheikh, El Sayed A
AU - Kamita, Shizuo G.
AU - Hammock, Bruce D.
PY - 2016/3/1
Y1 - 2016/3/1
N2 - Juvenile hormone analog (JHA) insecticides are biological and structural mimics of JH, a key insect developmental hormone. Toxic and anti-developmental effects of the JHA insecticides methoprene, fenoxycarb, and pyriproxyfen were investigated on the larval and pupal stages of Spodoptera littoralis and Spodoptera frugiperda. Bioassays showed that fenoxycarb has the highest toxicity and fastest speed of kill in 2nd instar S. littoralis. All three JHAs affected the development of 6th instar (i.e., final instar) and pupal S. frugiperda. JH esterase (JHE) is a critical enzyme that helps to regulate JH levels during insect development. JHE activity in the last instar S. littoralis and S. frugiperda was 11 and 23 nmol min-1 ml-1 hemolymph, respectively. Methoprene and pyriproxyfen showed poor inhibition of JHE activity from these insects, whereas fenoxycarb showed stronger inhibition. The inhibitory activity of fenoxycarb, however, was more than 1000-fold lower than that of OTFP, a highly potent inhibitor of JHEs. Surprisingly, topical application of methoprene, fenoxycarb or pyriproxyfen on 6th instars of S. littoralis and S. frugiperda prevented the dramatic reduction in JHE activity that was found in control insects. Our findings suggest that JHAs may function as JH agonists that play a disruptive role or a hormonal replacement role in S. littoralis and S. frugiperda.
AB - Juvenile hormone analog (JHA) insecticides are biological and structural mimics of JH, a key insect developmental hormone. Toxic and anti-developmental effects of the JHA insecticides methoprene, fenoxycarb, and pyriproxyfen were investigated on the larval and pupal stages of Spodoptera littoralis and Spodoptera frugiperda. Bioassays showed that fenoxycarb has the highest toxicity and fastest speed of kill in 2nd instar S. littoralis. All three JHAs affected the development of 6th instar (i.e., final instar) and pupal S. frugiperda. JH esterase (JHE) is a critical enzyme that helps to regulate JH levels during insect development. JHE activity in the last instar S. littoralis and S. frugiperda was 11 and 23 nmol min-1 ml-1 hemolymph, respectively. Methoprene and pyriproxyfen showed poor inhibition of JHE activity from these insects, whereas fenoxycarb showed stronger inhibition. The inhibitory activity of fenoxycarb, however, was more than 1000-fold lower than that of OTFP, a highly potent inhibitor of JHEs. Surprisingly, topical application of methoprene, fenoxycarb or pyriproxyfen on 6th instars of S. littoralis and S. frugiperda prevented the dramatic reduction in JHE activity that was found in control insects. Our findings suggest that JHAs may function as JH agonists that play a disruptive role or a hormonal replacement role in S. littoralis and S. frugiperda.
KW - Inhibition
KW - JH esterase
KW - Juvenile hormone (JH) analog insecticide
KW - S. frugiperda
KW - Spodoptera littoralis
UR - http://www.scopus.com/inward/record.url?scp=84960370692&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84960370692&partnerID=8YFLogxK
U2 - 10.1016/j.pestbp.2015.10.008
DO - 10.1016/j.pestbp.2015.10.008
M3 - Article
VL - 128
SP - 30
EP - 36
JO - Pesticide Biochemistry and Physiology
JF - Pesticide Biochemistry and Physiology
SN - 0048-3575
ER -