Jun 9, 2011 – Residuals and Formulations
QUESTION:
I have read in the "Cockroach Control Manual pg. 54" that insecticide residues from crack and crevice aerosols last longer than standard liquid insecticide residues. If I use Orthene crack and crevice aerosol will I get better results (% kill and better residual performance) versus using Orthene Pco in water at 1% solution and applying it with a crack and crevice tip?
ANSWER:
My thinking on this is that the same active ingredient in a stabilized aerosol formulation may last longer once applied than one that was mixed with water and applied as a spray solution. The reason for this, if it is true, could be the water factor. Organophosphates and carbamates in particular (and the acephate in Orthene products is an organophosphate) can be very sensitive to breakdown in water due to hydrolysis. This is even more so if the water used as the diluent has a high pH factor (high alkalinity) or if the mixture is allowed to sit overnight or longer before use. There could be substantial degradation of the active ingredient in the water itself. In aerosols there typically was no water in the solution, but petroleum hydrocarbons of some kind were used as the diluent, and this tends to help maintain the integrity of the insecticide molecules.
Aerosols offer one more advantage over liquid water based sprays, and that is the ability to keep the material in that crack or crevice when you apply it. If any of the solution runs out of the crevice it suddenly becomes a "spot" treatment, and if you are obligated by the product Label to apply the material ONLY as a crack and crevice treatment in some situation, either you now are treating off-label or you need to immediately clean up that exposed material. The propellent in many aerosols flashes off very quickly, leading to immediate drying of the spray from the can, and leaving only the active ingredient as a thin layer on the surface. This is one advantage of the area spray products such as Precor 2000 for fleas. It uses alcohol as a major part of the diluent, and this evaporates almost immediately upon application, leaving the treated surfaces dry within minutes.
The disadvantage to aerosol products is their cost, as well possibly as the disposal of a lot of empty aerosol cans. Most of these can be wrapped in newspaper and disposed of in a waste container, according to their labeling. But, mixing concentrate products in a hand sprayer with water is nearly always going to cost less than using an aerosol product for the same application - same square footage or linear coverage. So, I would agree that it is likely that aerosol products do last a bit longer than the same active ingredient mixed with water for application.
View past Ask Mr. Pest Control questions.
I have read in the "Cockroach Control Manual pg. 54" that insecticide residues from crack and crevice aerosols last longer than standard liquid insecticide residues. If I use Orthene crack and crevice aerosol will I get better results (% kill and better residual performance) versus using Orthene Pco in water at 1% solution and applying it with a crack and crevice tip?
ANSWER:
My thinking on this is that the same active ingredient in a stabilized aerosol formulation may last longer once applied than one that was mixed with water and applied as a spray solution. The reason for this, if it is true, could be the water factor. Organophosphates and carbamates in particular (and the acephate in Orthene products is an organophosphate) can be very sensitive to breakdown in water due to hydrolysis. This is even more so if the water used as the diluent has a high pH factor (high alkalinity) or if the mixture is allowed to sit overnight or longer before use. There could be substantial degradation of the active ingredient in the water itself. In aerosols there typically was no water in the solution, but petroleum hydrocarbons of some kind were used as the diluent, and this tends to help maintain the integrity of the insecticide molecules.
Aerosols offer one more advantage over liquid water based sprays, and that is the ability to keep the material in that crack or crevice when you apply it. If any of the solution runs out of the crevice it suddenly becomes a "spot" treatment, and if you are obligated by the product Label to apply the material ONLY as a crack and crevice treatment in some situation, either you now are treating off-label or you need to immediately clean up that exposed material. The propellent in many aerosols flashes off very quickly, leading to immediate drying of the spray from the can, and leaving only the active ingredient as a thin layer on the surface. This is one advantage of the area spray products such as Precor 2000 for fleas. It uses alcohol as a major part of the diluent, and this evaporates almost immediately upon application, leaving the treated surfaces dry within minutes.
The disadvantage to aerosol products is their cost, as well possibly as the disposal of a lot of empty aerosol cans. Most of these can be wrapped in newspaper and disposed of in a waste container, according to their labeling. But, mixing concentrate products in a hand sprayer with water is nearly always going to cost less than using an aerosol product for the same application - same square footage or linear coverage. So, I would agree that it is likely that aerosol products do last a bit longer than the same active ingredient mixed with water for application.
View past Ask Mr. Pest Control questions.
