Mar 13, 2012 – If It Can’t Stand The Heat, Stay Out Of Arizona
QUESTION:
Could you recommend an insecticide that I can mix in a spray tank which will hold up in the intense heat here in Arizona, and which would also be safe to use for the operator and around homes? I have tried many different products and have come up with mixed results. I am primarily targeting scorpions, earwigs, crickets and springtails. I understand that products with a low vapor pressure hold up better in the heat.
ANSWER:
It's tough to offer choices that may not meet the expectations of the end user. If you are looking for an active ingredient or a formulation that is going to last the entire time between monthly or quarterly services then it is not likely to happen. Heat in particular is going to be the enemy of synthetic molecules, and the active ingredient exposed to the high AZ temperatures is going to break apart much more quickly than the same a.i. used in a cooler area. At a seminar a few years ago one of our respected university research consultants made the statement that to expect ANY pyrethroid active ingredient to hold up more than a couple of weeks is probably unrealistic. We do hear conflicting opinions on this from the manufacturers, who may promise months of residual from their products, but we need to balance that opinion with those from unbiased experts.
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Could you recommend an insecticide that I can mix in a spray tank which will hold up in the intense heat here in Arizona, and which would also be safe to use for the operator and around homes? I have tried many different products and have come up with mixed results. I am primarily targeting scorpions, earwigs, crickets and springtails. I understand that products with a low vapor pressure hold up better in the heat.
ANSWER:
It's tough to offer choices that may not meet the expectations of the end user. If you are looking for an active ingredient or a formulation that is going to last the entire time between monthly or quarterly services then it is not likely to happen. Heat in particular is going to be the enemy of synthetic molecules, and the active ingredient exposed to the high AZ temperatures is going to break apart much more quickly than the same a.i. used in a cooler area. At a seminar a few years ago one of our respected university research consultants made the statement that to expect ANY pyrethroid active ingredient to hold up more than a couple of weeks is probably unrealistic. We do hear conflicting opinions on this from the manufacturers, who may promise months of residual from their products, but we need to balance that opinion with those from unbiased experts.
I tend to believe that two formulations offer you the longest residual. One of these is granules, which release the active ingredient more slowly and may offer the active ingredient molecules some protection from the environmental conditions. The other formulation is the microencapsulated products, where the active ingredient is essentially contained within the microscopic porous capsules, and released more slowly to the environment or onto the bug. Being within the capsule helps to protect the a.i. from water as well, and you probably do get the extended residual, although now we may be talking about a couple of weeks longer.
Microencapsulated formulations (we'll abbreviate it CS) offer a number of other benefits that fit nicely into your ideal product. Again, they would be highly unlikely to last from one service to the next, but at least you get a longer residual. The kind of surface you apply insecticides to will also dramatically affect the ability of the product to kill the pests. Porous surfaces like wood or concrete may soak up your spray and keep it from contacting the passing bug. CS products may be more likely to have the capsules resting on the surface where they then latch onto the passing bug and are carried on the bug while the a.i. oozes out and through its exoskeleton. Ideally you apply the product (any product) directly into the harborage sites of the pest, giving you the longest contact time between bug and active ingredient. For fast-moving critters like scorpions you just may not get the contact time needed if all you do is spray around the foundation.
As far as the question of safety to you and your customers, I firmly believe that any of the products currently on the market can be used with no risk to people or pets if they are used according to the label and you wear the appropriate safety equipment. We have moved away from the more toxic organophosphates and to the much less toxic pyrethroids and newer chemical families, and we are using these current products at much lower concentrations than we did the old materials. However, no matter what product you use, including all those natural plant-based products, if you do not follow the label directions and do not wear PPE and over-apply or apply to places not needed - now you create the scenario where problems may occur. I know that is talking around your question, but I believe it is the truth. Back to the microencapsulated products a moment - these formulations generally have a MUCH lower relative toxicity than the same active ingredient in a traditional liquid formulation, so they would again be a good choice in the area of "safety".
As far as the question on vapor pressure, this is a measure of how rapidly a substance converts to the vapor stage where it can drift away. The vapor pressure of our insecticides is pretty darned low, so volatility and loss to vapors would generally be a non-issue. The products that have a high vapor pressure are the fumigants, including vapona, although it's vapor pressure is very low for a fumigant, and herbicides like 2,4-D, which definitely vaporize in hot weather and easily drift off-site. However, yes, products with the lowest vapor pressures are least likely to be lost as vapors during hot weather.
All of these factors demonstrate the strong need for IPM for control of invading pests such as the ones you mention. Springtails rely on moisture, so discovering the moisture sources that support them and correcting that contributing condition will greatly reduce your reliance on insecticides. Scorpions, earwigs, and crickets are nocturnal, and hide all day under things on the soil. Removing these harborage opportunities reduces the populations of the bugs on the property, without having to spray in an effort to kill them all. A strong effort at exclusion (and you should charge the customer to provide this service) will keep these bugs out of the home, which is the primary goal, and again reduce the reliance on chemicals to do it all.
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