New records of Exopholis hypoleuca (Coleoptera: Scarabaeidae: Melolonthinae: Leucopholini) on Corymbia citriodora and Eucalyptus (Myrtaceae) with notes on its biology and population dynamics in North Sumatra, Indonesia

Abstract

The white grub of Exopholis hypoleuca (Wiedemann, 1819) (Coleoptera: Scarabaeidae: Melolonthinae: Leucopholini) is a known pest of several crops on Pacific Islands. This insect was observed feeding on the roots and shoots of Corymbia citriodora (Hook.) K.D. Hill & L.A.S. Johnson and Eucalyptus L'Hér. (Myrtaceae) plants in Aek Nauli, North Sumatra, Indonesia, which triggered its study. Management strategies of white grub are necessary to be developed because C. citriodora and Eucalyptus are largely planted in Indonesia for production of paper, pulp and viscose materials. The objectives of this study were to identify a white grub species attacking C. citriodora and Eucalyptusin Aek Nauli and to study key attributes of its biology (in the laboratory) and population dynamics (in the field) for 19 consecutive months. We also recorded new plant hosts and expanded the known geographical distribution of this insect. White grub species was identified as E. hypoleuca. The complete life span is 363.5 days and number of eggs per female is 43. Larvae feed mostly on the roots of C. citriodora and Eucalyptus while its adults on the leaves of Eucalyptus. Larvae were collected from August 2019 to February 2021, except in March 2020. Species identification and key biological attributes of E. hypoleuca are important information to develop management strategies of this insect. The population dynamics show activity of E. hypoleuca year-round in the studied area. This indicates that management activities must be conducted regularly against E. hypoleuca.