Survey of pathogens and parasitoids of Popillia japonica (Coleoptera: Scarabaeidae) in northwest Arkansas

Gradual Decline of Japanese Beetle (Coleoptera: Scarabaeidae) Populations in Michigan Follows Establishment of Ovavesicula popilliae (Microsporidia)

The purpose of this research was to document the incidence of Japanese beetle, Popillia japonica Newman (Coleoptera: Scarabaeidae), infection by the microsporidian pathogen, Ovavesicula popilliae Andreadis & Hanula (Microsporida: Pleistophoridae) while monitoring Japanese beetle populations at nine golf courses in Michigan from 1999 to 2018. We also compared the current distribution of the pathogen in Michigan to the known distribution in 1999. Beetles were sampled a total of seven different years, in three time periods: 1999-2000, 2005-2007, and 2015-2018. At these nine golf courses, O. popilliae infection rates of adults increased from 0.39% in 2000 to 29.5% in 2018, while Japanese beetle adult populations declined 73.2%, and Japanese beetle larval density declined 78.6% (from 1999 to 2018). In previous research, larval infection rates averaged at least twice the infection rates of adults, because all infections originate in the larval stage, and at least 75% of infected larvae die before pupation. This means that an adult infection rate of 29.5%, combined with previously observed 50% reductions in egg production by infected females, are consistent with the observed population declines. The current distribution of O. popilliae in southern Michigan was determined by sampling Japanese beetle larvae and adults at 38 sites in 2017 and 2018. Ovavesicula popilliae was found at 21 of 38 sites and in 16 of 21 counties, compared with two sites in one of 16 counties when it was first detected in Michigan in 1999 and 2000.

Characteristic Light and Electron Microscopic Features of Adelina melolonthae, a Coccidian Pathogen of the European Cockchafer, Melolontha melolontha (Coleoptera/Scarabaeidae)

PURPOSE

The aim of this study was to investigate and document the characteristic electron microscopic features of the oocyst of Adelina melolonthae, a coccidian pathogen of the European cockchafer, Melolontha melolontha (Coleoptera: Scarabaeidae).

METHODS

Larvae of M. melolontha were collected at Ordu, Turkey. Each larva was dissected in insect Ringer solution. Adeleid oocysts from the tissue that is suspected to Contain coccidian infections were examined under a light microscope (Zeiss), a scanning electron microscope (FEI Quanta 200) and transmission electron Microscope (Philips EM 208).

RESULTS

Spherical to ellipsoidal oocysts measure ca. 24-44.5 µm (mean 35.6 µm) in diameter (n = 50) and include up to twelve sporocysts. The oocyst wall has double layers; the outer layer measured 400-500 nm in thickness and the inner one 10-25 nm. Sporocysts including two sporozoites are rounded ca. 11-12.5 µm (mean 11.7 µm) in diameter. The sporocyst wall consisted of only one 70-80-nm-thick layer. The sporozoites are ellipsoidal and measured 9-11 µm length and 3-4 µm in width. Sporocysts include residual bodies.

CONCLUSION

In the present paper, the morphology and ultrastructure of the oocyst of A. melolonthae is documented for the first time and compared with other Adelina and coccidian species infecting insects. The results in this study confirm his identification and justify the classification as a separate species A. melolonthae, which differs from other Adelina species.

Seasonal Abundance, Defoliation, and Parasitism of Japanese Beetle (Coleoptera: Scarabaeidae) in Two Apple Cultivars

The Japanese beetle, Popillia japonica Newman, is an invasive insect to the United States that feeds on turfgrass roots as a larva and the foliage, flowers, and fruit of many major ornamental and agricultural crops, such as apple, as an adult. Despite its generalist feeding behavior, P. japonica shows preferences for certain plant species and cultivars. Classical biological control for P. japonica, including release of Istocheta aldrichi (Mensil), has been pursued in Minnesota. This study was conducted to assess the effects of apple cultivar on season-long abundance of adult P. japonica and their defoliation; and to assess effects of apple cultivar and P. japonica abundance and sex on parasitism of P. japonica by I. aldrichi. Sampling occurred during the summers of 2017 and 2018 on Zestar! and Honeycrisp cultivars in four different apple orchards. Abundance and defoliation of P. japonica was higher on Honeycrisp than Zestar!. Parasitism of P. japonica by I. aldrichi was higher for females than for males. In 2018, the relationship between parasitism of P. japonica and host density varied by cultivar. These findings may help growers determine which apple cultivars should be prioritized for scouting and management efforts and may provide an estimate of potential biological control by I. aldrichi in agricultural areas in the Midwest.