Nearly 80 years ago the U.S. military had a problem: Subterranean termites were wreaking havoc on wooden crates of munitions at the Panama Canal.
The job of testing chemicals to protect those crates fell to the U.S. Forest Service (USFS), which at the time had one of the world’s foremost termite scientists on staff. This work, followed by research on soil-applied termiticides to protect wooden structures, took place at the Harrison Experimental Forest near Gulfport, Miss., hence the name now synonymous with the studies. Today, USFS researchers evaluate the efficacy of every soil-applied liquid termiticide registered by federal and state regulatory agencies.
Termiticides are one of the few pesticides that require independent efficacy testing for registration, and must achieve 100 percent control for five years at four different USFS test sites, per guidelines adopted by the U.S. Environmental Protection Agency in 1996. The goal: Assure homeowners, lenders and pest management professionals that the materials actually work, which is important when you’re protecting people’s biggest investment.
BACK IN THE DAY. Two field tests developed decades ago are still used today. The ground board test, designed in the 1940s, involves clearing a 17-inch-square plot of land and treating it with the candidate termiticide. After drying, a small pine board is centered on the exposed, treated soil, and held in place with a brick. Open to changing weather conditions, the test provides a “worst-case scenario” for evaluating termiticide efficacy, said Guy Shelton, the research entomologist who today manages the USFS program. (Shelton began working at the USFS unit in January 2002.)
Data from a second test, the modified ground board or concrete slab test, is what EPA reviews in registration decisions. This test was introduced in 1967 to account for changes in American construction practices and involves covering treated soil with a polyethylene vapor barrier and pouring a 21-inch-square concrete slab around a 4-inch diameter PVC pipe placed at the center. Once the concrete has set, the vapor barrier is cut out and removed from the bottom of the pipe, and a small rectangular pine block is placed on the treated soil at the bottom of the pipe. To prevent weathering of the treated soil, the PVC pipe is capped.
For each concentration of termiticide being tested, the Forest Service conducts 10 replicate tests in each of its four test sites. Soil types and termite species vary in these sites, which are located in experimental forests in Mississippi, Florida, South Carolina and (until recently) Arizona. The “fairly simple” tests let researchers quickly read and record data from hundreds of test plots each day; “otherwise you’d be out there for months,” said Shelton.
Cooperators (or registrants) who pay for the tests can stop studies at any time, and they can extend them beyond the required five years as well. Once trials run about 10 years, they get “a little antsy” and usually end the study, said Shelton, who’d love to read tests “to infinity” to better determine when classes of chemicals become ineffective. USFS has data on chlordane going back 40-plus years; more than 20 years on organophosphates.
The Forest Service publishes test results annually after products are registered. It doesn’t release data on termiticides undergoing testing or that never gain registration.
TIMES ARE CHANGING. But some say the tests haven’t kept pace with changing chemistries. Originally they were designed to evaluate products like chlorinated hydrocarbons, organophosphates and pyrethroids that protect structures by repelling termites. Today’s non-repellent chemistries operate differently: Termites unknowingly pick up a lethal dose while tunneling through treated soil — they might even chew a little on the wood before transferring the active ingredient to the colony and dying.
In response, USFS increased the distance between test plots to prevent different products and concentrations from influencing tests nearby. It also changed how termite hits are evaluated. Originally, if termites damaged a wood block in a treated plot, the termiticide failed the test. Now, a damaged block is replaced with a new test block and evaluated again the next year to see if the termites come back.
“Just because they etched [the wood block] doesn’t mean that it’s a failure,” said Marie Knox, director of product development and research at Control Solutions.
Now whether a product passes or fails depends on what happens in subsequent years.
Repellents or non-repellents aside, termiticides “all serve the same purpose” in that they must protect wood from termite damage, and the tests have done a good job showing which products do this best, said Shelton.
But newer chemistries pose new challenges. “Let’s face it, the chemicals we use today are nothing like what was used 50 years ago,” said James Austin, global development manager for termite and mosquito control at BASF and a former PMP.
“Technology has really outpaced the simple confines of that test method in terms of it being predictable for future commercial success,” added Byron Reid, a senior principal scientist at the Environmental Science Unit of Bayer.
Additionally, fewer chemicals are passing the USFS tests. “In the last 10 years or so we put out a fair number of products that end up being withdrawn early; it is becoming more common,” said Shelton.
That’s because new chemicals are less persistent to meet the needs of agriculture, which prefers short-term residuals, and EPA, which doesn’t want products that last indefinitely in the soil.
“We’ve developed some tremendously effective insecticide chemistries that are doing great things in the agricultural market but every time we take one and put it into the testing paradigm for termiticides they fail because those attributes are not compatible with termite control,” said Reid.
To have a compound remain biologically available to kill termites in the field for five years after one application is “difficult to accomplish” and “that’s why you don’t see a lot of liquid termiticides being registered,” said Mark Coffelt, head of technical service in the Americas for Syngenta’s Turf, Ornamentals and Professional Pest Management division.
Experts said at some point, no new compounds will last in the soil for five years, a timeframe set in the 1950s so builders could offer guarantees on newly constructed homes. The toolkit of PMPs “would likely expand” if EPA required only two years of efficacy testing, like required in Japan and Australia, said Coffelt.
Although EPA prefers to see 100 percent control at all four test sites over five years, it has registered termiticides that achieved less. The State of Florida has its own guidelines and only requires a product to attain 90 percent efficacy over five years.
A LIMITATION. The Gulfport tests don’t evaluate real-world, post-construction applications. The horizontal ground board and concrete slab tests were designed to test the efficacy of pre-construction, sub-slab termiticide applications. “The data doesn’t show anything about post-construction” efficacy, even though EPA gives pretreat and post-construction labels to products passing the test, said Coffelt.
He says he would like USFS to employ a vertical test, similar to the wood stake test that it discontinued in the 1960s and is currently used in Australia and Japan. This might involve digging a hole, treating the removed soil, refilling the hole with the treated soil, and inserting a wood stake in the center so termites have to crawl through six to 12 inches of treated soil to reach the wood.
“I think a lot of the products will not meet performance standards” with a “much more realistic” test like this, compared to the existing tests where only a thin layer of soil is treated, Coffelt said.
In addition to the Gulfport tests, manufacturers must conduct infested-structure trials with university researchers or under an Experimental Use Permit (EUP) granted by the EPA to make claims beyond standard pretreat and post-construction labels. These trials may take two or more years and involve the treatment of hundreds of infested structures throughout the U.S.
“While the U.S. Forest Service information is useful, no test is comparable to real-world, practical experience,” said Chris Gorecki, vice president of operational support at Rollins.
Rollins uses the Gulfport data as a baseline for its termiticide evaluation process and then works with manufacturers to test products on infested structures. “Field testing allows us to see first-hand how a product will work within our protocols, test it with our equipment and determine whether the product will meet our needs,” Gorecki explained.
Infested home trials are “the ultimate test” of product efficacy given “the spatial complexity of an actual structure” while the Gulfport test involves “a 2-foot-square plot of land in a forest,” said Reid.
Still, the USFS tests have resulted in many successful products coming to market. In fact, of the hundreds of products evaluated over the decades, most have failed. This benefits the public by keeping ineffective or unsafe products off the market and reduces the liability of PMPs who warranty their termite protection service.
PMPs don’t have the ability themselves to generate this kind of data and they “can’t risk using a product on thousands of structures to find out years later that it doesn’t work,” said Bob Rosenberg, former CEO of the National Pest Management Association and who in the mid-1990s helped organize an industry response after concerns were raised about the termiticide Pryfon, which was manufactured by Mobay and contained the active ingredient isofenphos.
The organophosphate had passed the Gulfport tests but failed in the field in certain soil types and climatic conditions. That resulted in class-action lawsuits and millions of retreats, Rosenberg said. “That raised a lot of red flags about the validity of the data,” he added. At the time, he worked with EPA, ASPCRO (Association of Structural Pest Control Regulatory Officials) and RISE (Responsible Industry for a Sound Environment) to create the Termiticide Scientific Review Panel, an independent body of termite researchers that, among other things, explored new Gulfport test protocols. The group never reached consensus on a new test method.
“Getting people to agree on something is really, really hard when you have such diverse groups involved,” said University of Georgia termite expert Brian Forschler. “And getting a group of scientists to agree on something…you might as well forget it,” he said. While the current Gulfport tests aren’t perfect, “you need to have something” to test the efficacy of these products, he said.
THE REAL WORLD. Infested-structure field tests aren’t perfect, either. Unlike the Forest Service’s controlled test plots, “the real world is really messy,” Forschler said. Many variables may cause houses drop out of a study, from construction inconsistencies to the habits of the people living there. That raises questions: What constitutes a field-test failure, and are registrants cherry-picking data to shine the best light on their products, Forschler asked.
Dr. Richard Kramer, president of Innovative Pest Management in Brookeville, Md., has participated in infested-structure trials and finds this data useful. But he said the Gulfport ground board test mimics structure perimeters and is a better indicator for how a termiticide will perform over time when exposed to sunlight, rain, temperature, organic debris and general soil degradation.
“To me, the ground board test is it,” said Kramer. “If I don’t see a product that holds up more than five years on the ground board tests, I wouldn’t touch it,” he said.
PMPs are “more tied into the data than you think they are,” said Kevin Sweeney, who reviewed termiticides for registration at EPA before leaving to head regulatory affairs at Landis International, a consultancy that helps companies manage the regulatory process.
Having decades of data “gives you that really strong foundation and a strong history of how effective and how long the soil treatments work,” said Brad Kard, a termite researcher at Oklahoma State University who previously led the USFS program. Some products break down faster than others, and this information helps PMPs decide what products to use and when to retreat structures.
Donny Oswalt, owner of The Bug Doctor in Gadsden, Ala., and who has a Ph.D. in entomology, used Gulfport data to select termiticide products and has extrapolated it to craft treatment strategies, re-treatment intervals and contract stipulations.
It helps you justify guarantees in contracts covering termite damage repair, said Bob Kunst, president of Fischer Environmental in Mandeville, La. If you’ve led a person to believe you’ve solved his termite problem “then you ought to be able to stand behind it” and the Gulfport data helps you do this, he explained.
A GOOD JOB. Even critics recognize the value of the Gulfport tests. They are “very necessary” in that they provide “a historical relationship to all termiticides” and let you directly compare products using the same modality of testing, said BASF’s Austin.
“Without proper efficacy requirements, termiticide claims could undoubtedly be inaccurate,” added Coffelt.
“At the end of the day, I think the Forest Service testing has been working,” said Sweeney. But “certainly new protocols could be researched and adopted to provide maybe a better evaluation of exterior perimeter-only treatments, which I think is the rub for some of the companies.”
USFS currently is evaluating such a test method “so that we can try to keep up with the industry as much as that’s possible,” said Shelton. He is waiting for EPA and ASPCRO to sign off on the new “small scale” test protocol that is not radically different from what the agency is doing now. He hopes to unveil it in the Forest Service’s 2017 or 2018 annual report.
The USFS “can change the protocol if they want to, but it’s not going to change the behavior of the marketplace,” which puts more faith in real-world tests with infested structures, said Reid. And it is unlikely manufacturers will conduct the new tests unless EPA requires it to register a product, said Coffelt. (Already registrants may be on the hook for up to two years of USFS lab screening, the five years of field tests and two-plus years of infested-structure trials, in addition to research and development costs.)
Changing the paradigm for evaluating termiticides is “a big deal,” said Sweeney, who thinks it will be years before EPA feels comfortable enough with a new test method to change its registration guidelines.
In the meantime, the agency will continue to conduct the concrete slab test, which experts don’t see going away. The ground board tests, “depending on how useful the cooperators really feel they are and whether the EPA or ASPCRO really wants them, they could come or go in the future,” said Shelton.
The Forest Service protocol will remain “the gold standard” for testing soil-applied liquid termiticides, said Davis Daiker, who leads the Florida Department of Agriculture’s termiticide registration process.
Just don’t expect loads of new products to hit the market anytime soon. In 2015, only four termiticides were undergoing testing, USFS reported.
That’s a big departure from the late 1980s and early 1990s when “everyone saw a market opportunity” after Velsicol Chemical Corp. ceased production and sale of chlordane and there was “a proliferation of new technology, new chemicals” that needed testing, recalled Rosenberg.
With very effective, affordable liquid termiticides on the market today, manufacturers have little incentive to develop new products.
The author is a frequent contributor to PCT.