In 1998, a project was initiated in Armstrong Park in New Orleans to study the population dynamics of the Formosan subterranean termites, Coptotermes formosanus, especially in relation to bait treatments. This park study is the largest and longest-lasting research project involving Formosan termites and bait technology, and to date, five phases of research have been completed. This article focuses on the results of Phase V of the research which began in 2010 and was completed in 2015. This article focuses on the most recent research, Phase V, which investigated the use of baits for area-wide termite control.
Phase IV of the Armstrong Park project demonstrated that if no control measures are taken, a termite-free area will be re-populated by nearby colonies. But is it possible to maintain a termite-free area? Before 2010, all commercial baits employed a monitoring and baiting protocol using bait stations with wood monitoring pieces that were manually or electronically checked by technicians on site before an active bait was applied. Although a baiting program can be used to keep an area termite-free (Phase III), the monitoring-baiting protocol is labor intensive and therefore not economically sustainable for an area-wide project where hundreds of stations would need to be routinely opened and examined.
PROJECT BACKGROUND. In 2010, a durable bait, Recruit HD, became commercially available. It is comprised of cellulose powder with 0.5 percent noviflumuron and polymer binder (Eger et al. 2011) and an aging study showed that it remained efficacious even after being left in the field for five years (Eger et al. 2014).
A durable bait bypasses the monitoring segment to reduce labor, minimize disturbance of termites in the station, and can be used in a large area where diligent monitoring is not practical (Su 2007). Because this durable bait does not require diligent monitoring, we anticipate that it can serve as an economically sustainable tool to keep a large area termite free for as long as the bait program is maintained. This phase of study was carried out to demonstrate the concept at the Armstrong Park site (Su et al. 2016a).
By 2010, 14 Formosan colonies were found in the Park (Phase IV), but due to the limited availability of Recruit HD in 2010, and limited access to some areas of the park due to construction, baits could only be applied in 13 selected stations targeting five identified colonies (see figure 1A on). Of the 13 Recruit HD baits installed in September 2010, seven were substantially consumed (including four that were totally consumed) and replaced with fresh baits by November. Following bait consumption, activity of baited colonies began to decline, and by July 2011 none of the stations belonging to baited colonies harbored live termites (see Figure 2).
As park sites previously under construction became accessible, Recruit HD baits were installed in 26 additional Sentricon System stations between October 2011 (see figure 1B) and September 2012, resulting in total elimination of all detectable termite colonies (both Formosan and eastern subterranean termite) by December 2012 (see figure 2).
The total cessation of termite activity lasted five months until May 2013, which up until then was the longest time span of total absence of termite activity since monitoring for termite activity in the park began in 1998 (Messenger et al. 2005, Mullins et al. 2011, Su et al., 2016b). Because the foraging distance of a Formosan colony may extend up to 300 feet (King and Spink 1969), the lack of re-invasion from outside of the park for five months suggested that some of the larger and aggressive colonies capable of immediate re-invasion in the 300-foot wide zone outside the park border also may have been eliminated by consuming baits placed near the borders.
Formosan termites were again detected in three and one stations in May and June 2013, respectively (see figure 3A), and these four stations were found near the park border, indicating that it took five months for smaller and less aggressive colonies in the 300-foot wide outer zone to make their way to the park borders. These four stations were immediately baited in May and June, and after two months of bait consumption, termite activity ceased and the park became termite free again for another 12 months (see figure 2).
The prolonged absence of termite activity suggests that baits may have eliminated most of the termite populations surrounding the park. The last termite activity of this study was recorded in July 2014 from two stations, one each for Formosan and eastern subterranean termite (see figure 3B). Termites from both stations were relatively small, suggesting that they may have originated from alate pairs established in the spring of 2013 or 2014. Both were baited in July, and since September 2014, no termites have been found in any of the stations in the park.
As with commercial applications, Recruit HD baits in this study were left in the stations if not substantially consumed, and our results showed that these baits were intercepted by re-invading colonies of subterranean termites resulting in their elimination, and such interception and elimination events may occur multiple times in a single station. Recruit HD baits installed near a home, hence, can eliminate all detectable termite colonies within the property, making it a semi-permanent termite-free zone for as long as the bait program is maintained.
LESSONS LEARNED. Results of this long-term study at Armstrong Park has taught us several lessons:
- In an area with high termite pressure, it is a norm to have multiple colonies present in the neighborhood (Messenger et al. 2005).
- In an area with many termite colonies, elimination of a colony may result in the re-invasion by a neighboring colony, which has to be baited and subsequently eliminated (Messenger et al. 2005).
- A persistent baiting program can eliminate all detectable colonies in a large area and create termite free-zone within two years (Mullins et al. 2011).
- If surrounded by active termite populations, a termite free-zone may be fully re-occupied by termites from outside in 53 months (Su et al. 2016b).
- Placement of Recruit HD can produce a termite free-zone for as long as the bait program is maintained (Su et al. 2016a).
- Area-wide management of subterranean termites is a sustainable approach to managing subterranean termites. Sustainability, as defined by the World Commission on Environment and Development in 1987, must involve environmental, social and economic elements. Termite baits use less toxic insecticide, which addresses the environmental aspect, and are capable of managing termite populations for a community, which addresses the social need. The use of a durable bait now makes area-wide baiting economically sustainable from a service standpoint (Su et al. 2016a).
The author is a distinguished professor of entomology at the University of Florida, where his research on population ecology of subterranean termites and slow-acting control agents led to the development Dow AgroSciences’ Sentricon System.