Effects of methanol extracts of Mikania micrantha on the growth and development of the rhinoceros beetle, Oryctes rhinoceros Coleoptera Dynastidae
Acta Entomologica Sinica 55.9 (September 20): 1062-1068
(Aim) To explore the potential of Mikania micrantha on ecological control of the rhinoceros beetle, Oryctes rhinoceros. (Methods) The effects of methanol extracts of M. micrantha on O. rhinoceros was studied using dipping method and feeding method. (Results) M. micrantha extracts showed good activity on feeding amount, hatchability, pupation, emergency and larval development of O. rhinoceros. M. micrantha extracts had antifeedant activity against the 3rd larvae of O. rhinoceros, with a positive correlation between antifeedant rate and the concentration of extracts. The egg hatchability decreased significantly and the hatching time was delayed after O. rhinoceros was treated with M. micrantha extracts, with the hatchability of 66.66% and the hatching time being prolonged 3 d compared with the control. The mortality was 40.43% when the 1st instar larvae hatched from eggs treated with 10 mg/mL extracts. The body weight gain of the larvae was also restrained by the M. micrantha extracts, being 3.83 g and 4.53 g at 90 d after the M. micrantha extracts were added to the diets at the concentrations of 10 mg/mL and 5 mg/mL, respectively, while in the blank, the body weight gain was 6.87 g. M. micrantha extracts also inhibited the pupation of O. rhinoceros. The pupation time was delayed, and the number of deformed pupae increased after the larvae were treated with the M. micrantha extracts. M. micrantha extracts also decreased the emergence of O. rhinoceros and prolonged the emergence time. The deformity of the treated adults was increased, manifested as deformed wings, smaller body size, disorder in walking, etc. (Conclusion) M. micrantha extracts show good prospects to be exploited as botanical insect growth regulators and can be applied in O. rhinoceros control.