Date of Award

12-2018

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Division of Agriculture (SAFES)

Committee Member

Dr. Eric Benson, Committee Chair

Committee Member

Dr. Patricia Zungoli

Committee Member

Dr. William Bridges

Abstract

The dark rover ant, Brachymyrmex patagonicus Mayr, is a minute (~0.5 mm) dark brown or black formicine ant invasive from Argentina and Paraguay. In the southeastern United States, the dark rover ant is considered a nuisance pest, and is difficult to control. Recently, B. patagonicus has expanded its invasive range, especially in the southeastern United States. In South Carolina, this species has become more common in pest control accounts. Despite this, most of the biology and behavior of the dark rover ant remains unknown. The only official record of B. patagonicus in South Carolina is from 2010 in Horry County. Based on personal observation and complaints from pest control operators, it was apparent this species was present in other parts of the state, but its distribution was unknown. Each of the 45 remaining counties in South Carolina were surveyed to investigate the presence of the dark rover ant. Target areas were chosen in each county which received a high volume of traffic such as schools, hospitals, and government buildings, and were sampled. Brachymyrmex patagonicus was collected and positively identified in all counties of South Carolina, indicating its invasive range is state wide, and provided 45 new county records. A distribution map was developed using these data, which also includes the first official record in Horry County from 2010. Reports from pest control operators indicated that B. patagonicus became a secondary pest after suppression of the red imported fire ant, Solenopsis invicta Buren. A series of four samples were conducted at ten trees on Clemson University Main Campus to measure the changes in foraging activity of B. patagonicus after S. invicta suppression using pitfall traps, baits, and tree scans. One sample was conducted to establish a baseline for B. patagonicus foraging activity, then half of the trees were treated with Advion® (Syngenta Crop Protection Inc., 410 S Swing Rd, Greensboro, NC) fire ant bait, while the other half were left untreated to serve as a control. Then three more samples were conducted to measure the change in dark rover ant foraging activity. There was no significant difference in the number of B. patagonicus captured in pitfall traps before and after S. invicta suppression, and there was no significant difference in the number of dark rover ants in pitfalls in the treated area versus the untreated area. Also dark rover ants were no more likely to dominate a bait after the suppression of S. invicta. Data from tree scans indicated that the most commonly found co-occurring species with B. patagonicus were the red imported fire ant (S. invicta), Argentine ant (Linepithema humile (Mayr)), black carpenter ant (Camponotus pennsylvanicus (De Geer)), and field ants (Formica sp.). It has been widely reported from field observations that despite the fact that B. patagonicus co-occurs with other highly invasive or ecologically dominant ant species, it is not met with the same aggression levels as other species. A series of trials were conducted in a laboratory setting to confirm and quantify these interactions observed in the field. Brachymyrmex patagonius was paired against S. invicta, L. humile and Dorymyrmex bureni (Trager) to observe their interactions. Solenopsis invicta was also paired against L. humile and D. bureni to serve as a positive control for aggression. Ants were collected in the field and allowed to acclimate before being transferred to an experimental arena where they were observed for a period of five minutes, and their interactions scored according to a previously established agonism scale. Data indicate that the combinations including B. patagonicus versus L. humile, S. invicta, and D. bureni had a mean aggression score that was statistically significantly lower than the combinations including S. invicta versus L. humileand D. bureni. The combinations including dark rover ants versus other ecologically dominant or invasive ants also yielded mean aggression scores that were not significantly different from one another; as did the combinations including S. invicta versus L. humile and D. bureni The data indicate that B. patagonicus is universally met with lower levels of aggression, corroborating field observations. The cause of this interaction remains unknown. Future research should focus on both size and chemical interactions as potential causes for this unique interaction.

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