How does flooding impact the effectiveness of AlwaysActive termite baits? Joanne George, Professional Pest Business Manager for Corteva Agriscience, shares the answer.
Since the introduction of Sentricon AlwaysActive to the market six years ago, pest managers have often asked me the same question: how do the in-ground termiticide rods hold up in extreme weather conditions, particularly to floodwater? In locations subject to seasonal tropical rainfall, and areas hit by unexpected flooding, such as the Mid North Coast of NSW back in March, it is an important question for pest managers to be asking.
To answer this, we need to look at what happens to both the active ingredient and the bait matrix when a termiticide rod is immersed in water for an extended period. Floodwater studies conducted over the last ten or so years give us the information we need.
So let’s look at the first point: what happens to the active ingredient when a termiticide rod is immersed in water for a long time?
Dow AgroSciences (which became Corteva Agriscience in 2019) undertook the first floodwater study in November 2010 in the US. Recruit HD is the name for the AlwaysActive rods in the US, the only difference being that the active ingredient is 0.5% noviflumuron, not hexaflumuron, as it is here in Australia. The composition of the rod matrix is exactly the same.
The 2010 study saw one Recruit HD rod being placed inside each Sentricon station, which was then placed inside a jar that was filled with purified water. The Sentricon rods were exposed to these simulated flooding conditions for up to three months. The water in the jar was analysed to determine the concentration of noviflumuron on the day of flooding and monthly up to three months.
The study revealed some significant findings. Firstly, that the concentration of active ingredient in water around the rods was extremely low and below the acute toxicity level for even the most sensitive aquatic species. Interestingly, the concentration of the active ingredient in the water did not increase with length of time that the Sentricon rod was subject to flooding. It was concluded that any free active ingredient is locked into the soil matrix, even when flooded, and does not move into the surrounding environment.
This means that when the rods are subjected to flooding, even over an extended period of time, the AI essentially remains within the rod and there is very little impact on the surrounding environment.
The second study was conducted in 2015 on the Australia AlwaysActive termiticide rods, which contain 0.5% hexaflumuron. Samples of the flood solution were taken on day one, day 36 and day 92 and were analysed to determine the concentration of hexaflumuron in the flood solutions.
The findings were the same as in the original US study; there was no significant difference in the level of active ingredient in the water between day one and day 92. The researchers also concluded that it was likely that any hexaflumuron measured in the simulated stagnant floodwater was rinsed off the exterior of the rod rather than having leached from the rod itself.
The design of both of the studies represent a worse-case scenario, as the length of time the rods were flooded was excessive, at three months in total. What they show is that even after three months, the level of active ingredient found in the floodwater was negligible.
So, on to the second point: what happens to the matrix when the bait is immersed in water for an extended period?
Back in 2017, I decided to do my own floodwater experiment at home, so I could see the results for myself. I put an AlwaysActive rod in a jar and immersed it fully in water for over a year. Figure 1 was taken the day it was put in the jug, and I checked it at three months (Figure 2) and again at six months (Figure 3). As you can see, a crack formed after three months, but that is totally normal and to be expected. Its condition hadn’t changed by the six month mark, nor after 12 months. It was still as solid as it was on day one, which is pretty outstanding in terms of durability.
To see this in action in a real-life situation, we can look at the city of New Orleans in the US, where much of the city is protected by the Sentricon System. Several years ago, residents battled with hurricane Matthew. Due to the subsequent floodwaters, many of the Sentricon stations sat in stagnant water for a few weeks. Dow AgroSciences (Corteva Agrisciences) collected some of the storm-battered baits from the floodwaters and tested them for their palatability. In the lab, termites readily accepted the termiticide rods despite excessive exposure to floodwater giving them a visibly gnarled appearance. It was also reported that in New Orleans, the Sentricon stations were again targeted by termites after the water had subsided, demonstrating the palatability and durability of the termiticide rods in yet again a worse-case scenario.
What does all this mean for pest managers? Well, that even in the worse possible scenario – shown in lab tests and real-life conditions – there’s minimal leaching of the active ingredient and degradation of the rod after excessive water exposure. The CodeMark-certified Sentricon system is an environmentally friendly and highly durable option for protecting structures, which can be used as both a preventative and curative system. Pest managers can assure homeowners that their termite management system will stand up to even the worst of Australia’s wild and unpredictable weather.
Joanne George, Professional Pest Business Manager, Corteva Agriscience