Masters Theses

Date of Award

12-1999

Degree Type

Thesis

Degree Name

Master of Science

Major

Entomology and Plant Pathology

Major Professor

Jerome F. Grant

Committee Members

Paris Lambdin, Roberto Pereira

Abstract

The gypsy moth, Lymantria dispar, is not native to the U.S., but was introduced into Massachusetts in 1869 by Etienne Leopold Trouvelot (Doane and McManus 1981). This insect subsequently escaped into the surrounding forests and is now found throughout the northeastern U.S. The gypsy moth feeds on more than 300 tree species and defoliates an average of 2 million forested hectares per year (Reardon and Hajek 1998). It is estimated that the gypsy moth front will be in Bristol, TN, by 2005 and Knoxville, TN, by 2015 if no efforts are made to slow the gypsy moth (Liebhold 1998). The establishment of the gypsy moth in Tennessee would greatly impact this area. In Tennessee, one-half (5.5 million hectares) of the state is forested, 78% of these forests are composed of oaks and hickories, and 30% are highly susceptible to gypsy moth (Kauffman 1996). In 1995, the forestry industry in Tennessee employed more than 44,000 persons, with an estimated payroll greater than $827 million (Kauffman 1996). Gypsy moth was first detected in Tennessee in 1972 (Kauffman 1998), and has since been captured in 64 counties throughout the state. However, no studies have been undertaken to examine for the presence of natural enemies of the gypsy moth in Tennessee. Therefore, the specific objectives of this research were to: 1) monitor gypsy moth larval populations and evaluate the presence of Entomophaga maimaiga, a fungal pathogen which has caused extensive epizootics of gypsy moth in the northeastern U.S. (Hajek et al. 1995), 2) conduct soil bioassays to assess presence of E. maimaiga and other entomopathogens, and 3) examine for biological control agents (predators and parasitoids of gypsy moth eggs and pupae) in Tennessee.

Although 60 (1998) to 120 (1999) burlaped trees were monitored weekly during 1998 and biweekly during 1999, no gypsy moth larvae were collected at any of the sampling sites. These data are not surprising due to the eradication efforts of the Tennessee Department of Agriculture who quickly treat any infestations found within Tennessee. During this two-year study, 6,600 gypsy moth larvae were exposed to 660 soil and duff samples to assay for the presence of E. maimaiga. No E. maimaiga was recovered during this study; however, two other fungal pathogens, Metarhizium anisopliae and Beauveria bassiana, were found to infect gypsy moth larvae (<0.2% of all larvae). Also, more than 30 viable egg masses were collected during winter 1998 from three trees in Cumberland County. No parasitoids emerged from field-collected egg masses. Lastly, between 26 August and 24 September 1999, 123 ants (representing 5 genera) were collected from both pupae and egg masses in the field. Of 330 field-placed, freezer-stored pupae, 79 (24%) were damaged by predators. Of the 330 egg masses placed in the field, 112 (34%) were damaged. The most commonly collected ant genera were Aphaenogaster (43%), Paratrechina (42%), and Camponotus or carpenter ants (11%).

Further effort should be taken to monitor for gypsy moth larvae along with associated parasitoids or pathogens in the field. Testing of soil and duff should be continued to assess for the presence of E. maimaiga into Tennessee. If this fungal pathogen is not recovered, release of resting spores should be made in areas where outbreak populations of gypsy moth occur and efforts should be undertaken to recover E. maimaiga. Lastly, monitoring of predators and parasitoids of gypsy moth pupae and eggs is needed to determine seasonality, diversity, and impact of species involved. If permanent gypsy moth populations become established and widespread, eradication programs will no longer be economically feasible. Such research will enable managers to develop appropriate management strategies that may provide long-term reductions of gypsy moth populations and protect Tennessee's forests.

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