Influence of ultrasound on juvenile hormone titers in Monochamus alternatus Hope (Coleoptera: Cerambycidae)
Abiotic stress factors can significantly affect insects. In particular, the stressful effects of exposure to ultrasound on insects are considered important. In the present study, we investigated the effects of ultrasound on the important global pest Monochamus alternatus (Coleoptera: Cerambycidae) which is the main vector of the pinewood nematode. We exposed M. alternatus adults (aged 1 day, 3 days, and 5 days) to ultrasound at different frequencies (using two ultrasonic devices, i.e. LHC20 with a mixture of frequencies at 35 kHz, 70 kHz, and 105 kHz; and GFG 8016G at two separate frequencies of 30 kHz and 60 kHz) for different periods of time (1 h, 12 h, and 24 h) before evaluating the juvenile hormone III (JHIII) titers. All of the ultrasound treatments significantly decreased the JHIII titers in M. alternatus adults. The decreases in the JHIII titers due to ultrasound exposure did not differ according to sex, but the effects on beetles of different ages differed significantly depending on the duration of exposure. The decreases in the JHIII titers were highest in male and female beetles after exposure to ultrasound for 12 h. Following exposure to ultrasound for any time period, the decreases in the JHIII titers were lower in adults aged 3 days than those aged 1 day and 5 days. The different ultrasonic frequencies led to variable decreases in the JHIII titers in M. alternatus adults, where the greatest decreases occurred in beetles exposed to ultrasound at 60 kHz. Our results indicate that ultrasound can negatively affect the normal JHIII levels and it may further disrupt sexual maturation by M. alternatus adults.
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