Date of Award

5-2014

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Ecology and Environmental Sciences

Advisor

Eleanor Groden

Second Committee Member

Francis A. Drummond

Third Committee Member

Andrei Alyokhin

Abstract

Myrmica rubra (L.) is an invasive, pestiferous ant in isolated sites in the northeastern United States and Canada. Its aggressive nature and painful sting can make it impossible for residents of heavily infested areas to use their lawns and gardens and endanger those who are sensitive to its venom. This species' ability to reach high densities and its generalist habits allow it to outcompete and virtually eliminate native ants at some sites. This could potentially lead to ecosystem level changes as ground dwelling ants turn over the soil and large changes in the ant community could lead to a change in the dissemination of nutrients as well an alteration in seed dispersal. The goal of this research was to expand our understanding of colony movement dynamics and to develop safe and effective methods to avoid further spread of this ant using repellents. Longterm monitoring of artificial nesting substrates, marking colonies, and laboratory and field trials provided new details about colony movement and M. rubra nesting preferences.

Measurements from occupied and unoccupied nesting substrates revealed that colonies prefer cool, moist soil conditions. I found that colonies occupy the most nesting sites in the early spring. As the spring and summer season progresses most colonies emigrate from an occupied nest site or coalesce with other colonies so that the number of occupied nest sites in an area decreases. Marking worker ants with paint demonstrated that nests share individuals with other nests up to several meters away. This information is important for management of this species because it reveals which areas may be most vulnerable to immigration and that nests should not be treated singly, but considered as part of a network.

Numerous assays were performed to evaluate the repellency of materials with low mammalian toxicity. The plant extracts spearmint, peppermint, D-limonene, and neem were tested in both the laboratory and the field against colonies searching for a nest site. All four extracts applied to pots of soil in the laboratory were effective at restricting colonization to some extent. In the field, all extracts were successful in repelling colonization of plant pots for several weeks indicating that these substances have the potential to protect potted plants from colonies in search of a nest. Cedar mulch as well as entomopathogenic nematodes and fungi were also tested for repellency in the laboratory as potential barriers to colonization, but these materials neither prevented colonization or caused colonies to emigrate.

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