Jan 20, 2011 - Works Good, Lasts Awhile
QUESTION:
What is the residual of Tempo SC and Suspend SC insecticides?
ANSWER:
Like the weather forecasters, it pays to talk in really vague ways when trying to pin down just how long an insecticide active ingredient will last. There are just a lot of variables that can affect that active ingredient, and different chemical families may behave in different ways. For example, the old organophosphates and carbamates (diazinon, dursban, malathion, etc.) were highly susceptible to degradation due to the pH of the water used to dilute them, or the pH of the surface they were applied to. They also were very susceptible to rapid breakdown when exposed to UV light or when retained in just water. The same chlorpyrifos that might last 15 years in the soil under a house for termites could disappear within a few days or weeks when applied outside for ants or fleas. A lot of active ingredients of pesticides latch onto organic material, so soils rich in organic matter might tie up the active ingredient so that little of it is available to the passing bug or to weeds.
Synthetic pyrethroids, however, are much less subject to degradation from these environmental effects, but they still degrade fairly quickly. This is our two-headed dragon, and the loss of persistent insecticides was demanded by those opposed to our use of them due to fears that the active ingredient that hangs around too long can also be more likely to travel off site, and this fear does have some justification. Because pyrethroids can possibly be very toxic to aquatic invertebrates at very low levels, you now are seeing states implementing regulations regarding the use of these materials wherever they may get into surface waters. Another consideration in all of this is that "residual", for our purposes, really refers to how long it lasts and still is effective in some manner for pest management. The molecule could be detected on a surface long after enough of it has degraded so that it no longer kills the roaches or fleas or other bugs. Since chemicals degrade by a "half-life" - a bit at a time - they do not just suddenly blink out of existence.
So, with this long winded preamble, what is the answer to your question? At a seminar one time, where a few of our respected university consultants and researchers were present, the comment was made that it would be surprising to find any of the pyrethroids, used outdoors, to give more than 2 weeks of residual effectiveness. This obviously is open for argument, and there are ways to lengthen that residual by different formulations. For example, placing the active ingredient within a granular material could protect it from the elements, allowing it to escape more slowly, and for this reason one vendor states their granular pyrethroid gives up to 3 months of effectiveness. The a.i. could be contained within microscopic porous capsules - microencapsulated formulations - protecting the a.i. from water and other elements and extending the residual. You could apply the material indoors or within protected crevices around the exterior where water and sunlight do not affect it directly, adding to its longevity.
Certain surfaces - porous, wood, concrete, alkaline, shiny - can all have their effect too, on how long the a.i. lasts or how available it is to the passing bug, so we keep that in mind and use a formulation best suited for that surface. In this area too is the fact that spraying insecticides onto greasy surfaces, such as in many kitchens, is going to seriously harm the effectiveness. Grease just ties up active ingredients so they are no longer available. Sanitation and cleaning thus have another reason for helping us in pest management.
I myself also believe that where the repellency of pyrethoids works to our advantage there may be a repellent effect long after the killing effect is gone, such as the ability to keep spiders off surfaces that were treated many weeks earlier. But, if we keep our experts' thoughts in mind, we probably should not plan on having these active ingredients (and Tempo and Suspend are both pyrethroids) lasting more than 3 weeks or so. I know darned well I am going to raise the hairs on the backs of the necks of some manufacturer representatives with this answer, but we'll still toss it out there and see what jumps on it.
View past Ask Mr. Pest Control questions.
What is the residual of Tempo SC and Suspend SC insecticides?
ANSWER:
Like the weather forecasters, it pays to talk in really vague ways when trying to pin down just how long an insecticide active ingredient will last. There are just a lot of variables that can affect that active ingredient, and different chemical families may behave in different ways. For example, the old organophosphates and carbamates (diazinon, dursban, malathion, etc.) were highly susceptible to degradation due to the pH of the water used to dilute them, or the pH of the surface they were applied to. They also were very susceptible to rapid breakdown when exposed to UV light or when retained in just water. The same chlorpyrifos that might last 15 years in the soil under a house for termites could disappear within a few days or weeks when applied outside for ants or fleas. A lot of active ingredients of pesticides latch onto organic material, so soils rich in organic matter might tie up the active ingredient so that little of it is available to the passing bug or to weeds.
Synthetic pyrethroids, however, are much less subject to degradation from these environmental effects, but they still degrade fairly quickly. This is our two-headed dragon, and the loss of persistent insecticides was demanded by those opposed to our use of them due to fears that the active ingredient that hangs around too long can also be more likely to travel off site, and this fear does have some justification. Because pyrethroids can possibly be very toxic to aquatic invertebrates at very low levels, you now are seeing states implementing regulations regarding the use of these materials wherever they may get into surface waters. Another consideration in all of this is that "residual", for our purposes, really refers to how long it lasts and still is effective in some manner for pest management. The molecule could be detected on a surface long after enough of it has degraded so that it no longer kills the roaches or fleas or other bugs. Since chemicals degrade by a "half-life" - a bit at a time - they do not just suddenly blink out of existence.
So, with this long winded preamble, what is the answer to your question? At a seminar one time, where a few of our respected university consultants and researchers were present, the comment was made that it would be surprising to find any of the pyrethroids, used outdoors, to give more than 2 weeks of residual effectiveness. This obviously is open for argument, and there are ways to lengthen that residual by different formulations. For example, placing the active ingredient within a granular material could protect it from the elements, allowing it to escape more slowly, and for this reason one vendor states their granular pyrethroid gives up to 3 months of effectiveness. The a.i. could be contained within microscopic porous capsules - microencapsulated formulations - protecting the a.i. from water and other elements and extending the residual. You could apply the material indoors or within protected crevices around the exterior where water and sunlight do not affect it directly, adding to its longevity.
Certain surfaces - porous, wood, concrete, alkaline, shiny - can all have their effect too, on how long the a.i. lasts or how available it is to the passing bug, so we keep that in mind and use a formulation best suited for that surface. In this area too is the fact that spraying insecticides onto greasy surfaces, such as in many kitchens, is going to seriously harm the effectiveness. Grease just ties up active ingredients so they are no longer available. Sanitation and cleaning thus have another reason for helping us in pest management.
I myself also believe that where the repellency of pyrethoids works to our advantage there may be a repellent effect long after the killing effect is gone, such as the ability to keep spiders off surfaces that were treated many weeks earlier. But, if we keep our experts' thoughts in mind, we probably should not plan on having these active ingredients (and Tempo and Suspend are both pyrethroids) lasting more than 3 weeks or so. I know darned well I am going to raise the hairs on the backs of the necks of some manufacturer representatives with this answer, but we'll still toss it out there and see what jumps on it.
View past Ask Mr. Pest Control questions.
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