Date of Graduation

8-2013

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Entomology (PhD)

Degree Level

Graduate

Department

Entomology

Advisor

Donald Steinrkaus

Committee Member

Donn Johnson

Second Committee Member

Fiona Goggin

Third Committee Member

Mike Richardson

Fourth Committee Member

Fred Spiegel

Abstract

Japanese beetles are a relatively new pest to Arkansas. During my Ph.D. research I investigated the pathogens and environmental factors influencing Japanese beetle populations in the state. The prevalence of various pathogens and parasitoids attacking Popillia japonica were recorded annually from wild populations. Of specific interest was the microsporidian pathogen Ovavesicula popilliae, which I introduced as a biological control agent in the state. Details of the relationship between this pathogen and the Japanese beetle were investigated, including dose response, host range, and spore production. Additionally, annual abundance of the beetle in the region was recorded and tracked over the course of 4 years using soil sampling for larvae and pheromone traps for adults. Outdoor and indoor rearing methods were developed, and the density of these populations were recorded and compared to wild populations and temperature data, allowing us to model climate impact on the beetle.

Results from these studies showed that, naturally occurring pathogens, such as Stictospora villani, Ovavesicula popilliae and Adelina sp., and parasitoids appeared to have minimal influence on the beetle populations in this region. In the case of O. popilliae, low levels of the pathogen appeared in the area naturally. This pathogen also has a narrow physiological host range outside of the Japanese beetle, primarily in other scarab larvae. O. popilliae also appears to primarily infect Japanese beetle larvae and was incapable of infecting adult beetles. Infected larvae which survived to adulthood remained infected, with the adults capable of producing on average 25 million spores. In comparison, high summer temperatures and lack of rain reduced late summer populations of larvae.

In 2010, O. popilliae was released at four locations in Northwest Arkansas. In 2011 it was detected at one of those locations. A second introduction of O. popilliae was made in 2012. The results from this classical biological control effort involving the release of O. popilliae require further monitoring to confirm establishment. This information can be used to help establish long term control of this new pest in the Southern United States. This information will be of use to fruit growers, horticulturalists, turf managers, nursery operators, and homeowners.

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