|[Image: Illustration of a termite]|
|[Image: Photo of Gregg Henderson]|
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I remember watching a science fiction television program as a child where the residents of a house were being attacked by giant termites the size of small cars from an alien world. The termites ate slowly through the house, horrifying the couple inside. A similar fear occurs in some residents of Louisiana when they find out they are under siege by the invasive and highly destructive Formosan subterranean termite.
Although not much smaller than a rice grain and similar in color, the Formosan subterranean termite worker may have several million brothers and sisters with the same mindset – find and eat wood. A single colony’s foraging area has been documented to encompass the area of an entire football field. The cellulose they pursue may be a 600-year-old live oak or a modest, not-as-old home. In time, both can be destroyed by the colony.
Originally hopping a ride to the United States on military ships returning from the Pacific after World War II, the Formosan subterranean termite became widespread in the state within the past 10 years. Boasting the highest populations of Formosan subterranean termites in the continental United States, Louisiana has been dealing with the destructive tendencies of these termites for 65 years now. They truly are the alien giants of the termite world.
The unusually large flights of males and females flying in the early evening near light posts were the first signs that something new was in town. The winged termites, known as alates, that emerge from numerous colony nests in the ground, tree or home around Mother’s Day every year can shut down outside evening events any day they choose between April and end of June. People out and about on the nights of these alate flights are at risk of gagging from inhaling a bunch of alates. There are that many flying at a time. The alates are attracted to lights, which serve as the meeting place between the sexes that will result in a monogamous relationship between king and queen that can last for decades.
Starting in 1989, when Formosan populations in the French Quarter were considered at crisis levels by residents and pest control operators alike, LSU AgCenter scientists deployed 15 light-traps to collect alates in the French Quarter and Greater New Orleans. Originally, the idea was just to see how widespread they were in the Quarter. However, it was soon determined that yearly counts were one of the few measures (indirect as they may be) that could be used to determine growth or decline of the infestation.
The use of alates to measure the health and size of these underground aliens is an imperfect science because we don’t understand many of the intrinsic and environmental factors that control their numbers in a colony. While we know the colony must be large, having developed for at least seven years if it is to produce alates, we don’t really know how various stresses can affect their output. From the 20-year census we have gained some insight into these questions.
From 1989 through 1996, growth in the number of alates was recorded. These data were invaluable to Rep. Bob Livingston, who at that time was chair of the House Appropriations Committee, as justification for funding a major initiative to control Formosan subterranean termites. Operation Full Stop, as the effort was named, has since garnered more than $28 million in federal funding to study and demonstrate control methods since then. Over the 20 years, three drops in alate catches stand out. Two were linked to major droughts and one to Hurricane Katrina.
Both in the mid-1990s and again starting in 2000, major droughts were recorded in Louisiana. Dry conditions make it difficult for Formosan subterranean termites to persist in above-ground carton nests for long because they require a constant source of water. In addition, dry soil is harder to tunnel through to get to food sources without major desiccation casualties among the soft-bodied workers. Alate production becomes too costly to the colony.
Meanwhile, the floods caused by levee failures in 2005 in the aftermath of Hurricane Katrina kept much of New Orleans under water for close to one month. This resulted in the highest percentage drop in numbers from the previous year over the 20-year census. More than a 70 percent drop in numbers was seen from the pre-Katrina 2005 count to the post- Katrina 2006 count. However, climate is not the only reason that alate numbers dropped in New Orleans, especially in the French Quarter. The proposed research project, which was funded by Congress, was directed at using only colony reduction products. Nonrepellent termiticides and baits were just coming onto the market, and both represented a new paradigm in termite control – whole colony kill. Figure 2 shows the total alate catch in the French Quarter for a condensed set of years. A clear and persistent decline is evident that almost certainly was due to the efforts of the LSU AgCenter, the U.S. Department of Agriculture’s Agricultural Research Service, the Louisiana Department of Agriculture and Forestry, New Orleans Mosquito and Termite Control Board and local pest control operators – all partners in Operation Full Stop. The 2008 alate catches were more in line with 1989 numbers.
While success is clear, and using alates to measure changes in populations appears useful, we must keep in mind that in 1989 we were thought to be in crisis mode with this termite giant.
Gregg Henderson, Paul K. Adams Professor of Urban Entomology, Department of Entomology, LSU AgCenter, Baton Rouge, La.
(This article was published in the fall 2010 issue of Louisiana Agriculture Magazine.)