Perimeter treatments are essential to good pest management. But with many years of experience training technicians, I have seen mistakes made which can be easily corrected with explanation of why what is being done is not correct. Let’s discuss some of the issues:

1. Mixing directions may be different for perimeter use. Mixing a product for perimeter use may be different than mixing a product in a one-gallon compressed-air sprayer. Rather than just adding a certain number of ounces, grams or milliliters per gallon, perimeter treatments are based on putting out a specified amount of the pesticide in a given area.

For perimeter treatment, you need to know how many gallons you will apply per 1,000 square feet. Based on this, you can figure out how much product should be added per tank mix. For example, let’s assume you normally apply about 2 gallons per 1,000 square feet. If the perimeter treatment directions on the label say to apply 1 ounce of the product per 1,000 square feet, then ½ ounce or half of the product required needs to be in each gallon applied. In this case, since each gallon of water should contain ½ ounce of the product, you can calculate that 25 ounces would need to be mixed into a 50-gallon tank.

It would be a mistake to simply take the amount of product needed for a one-gallon tank and increase this amount 50 times to mix 50 gallons for perimeter use if specific perimeter treatment directions are on the label. Always follow the label as to the amount of material to be applied for the type of treatment being done.

2. Do not refill compressed air sprayer from truck tank. I have seen technicians refill a one-gallon sprayer from the product mixed in the truck-mounted sprayer. This may seem reasonable when the same product is being used for both tank mixes. The problem is that the two applications are different. This is a mistake that will result in too little material being applied.

The concept between a one-gallon sprayer and truck sprayer is different. With a one-gallon sprayer, you are mixing a product at a higher concentration and applying it at a low volume. With a truck-mounted sprayer you are mixing a product at a low concentration and applying it at a higher volume. In the end, the amount of active pesticide applied to the treatment area may be similar but accomplished in two different ways.

The mistake is when you mix the two methods. When a one-gallon sprayer is refilled from a tank intended for perimeter use, you are now applying a low concentration of the pesticide at a low volume. Too little material will be used and results may be poor.

3. Understanding where pyrethroids can be used. Some technicians are uncertain about the restrictions put on pyrethroid application to the perimeter of structures. The explanation I would offer is that pyrethroid use on the perimeter must be limited to spot or crack-and-crevice treatment above a non-porous surface. In plain words, any treatment above concrete or asphalt on the perimeter of a home must be a spot or crack-and-crevice treatment. By definition, a spot treatment is less than 2 square feet.

When above grass, a broader treatment can be done following guidelines for distances up the wall and out from the foundation as listed on the label. If there are areas that need to be treated above concrete and asphalt, they can be, but these are limited to the type of treatments described. There are other details, but these guidelines answer most questions about where treatments can be made.

The goal of these restrictions is to prevent pyrethroids from being washed off of a non-porous surface into drains. When you understand the why, what to do and what not to do makes a lot more sense.

4. Do not spray herbs or vegetables. Many people enjoy planting a garden or herb bed. In some cases, these plants may be growing next to the house where we would normally treat. The products we have are not labeled nor intended to be used around plants grown for food. You can quickly offend gardeners by ruining their hard work. Practice recognizing common vegetables and herbs. If in doubt, ask if there are any edible plants being grown in the flower beds. Inspecting the perimeter of a house you are not familiar with before treating can help you avoid making this mistake.

5. Do not apply granules to hard surfaces. Granules are a useful tool for perimeter treatment. They have the advantage of being able to get to the soil level through heavy vegetation. But unwanted results can occur when granules are carelessly applied to sidewalks or driveways. Not only can the product be washed into storm drains, it also can be picked up by shoes and carried into homes. Granules on packed dirt with no grass also can be picked up by dogs and ingested as they clean their paws. And granules can stain concrete if they are not removed.

Granule application needs to be made so as to prevent the granules from being left on hard surfaces. If they do end up on sidewalks or driveways, they should be swept into the grass or landscape beds. This means you need to be prepared and have a broom ready to correct this problem.

I believe all of these points are worth reviewing. Sometimes we assume things are being done correctly when they may not be. I also believe that explaining why these are the correct things to do is more valuable and more effective than just giving out a list of do’s and don’ts.

The author is a member of the Copesan Technical Committee. He holds bachelor’s and Ph.D. degrees in entomology from Texas A&M University and he currently serves as training and technical manager of Beaumont, Texas-based Bill Clark Pest Control.


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