Good Choice: How to Select Pesticides

Last week, I received a text from a technician inquiring if a granular bait would hold up to rain that was expected that day. I realized then that we need to get back to basics in our training periodically. It is really no different than re-reading our labels to keep our mind fresh on that particular product. Sometimes we need a refresher on what to use based on the pest, its surrounding environment, its habits, and, of course, weather conditions at the time of application.

In this case, a simple “no” would have been of little help. I had to explain that the granular bait was made by mixing materials together like a corn grit-styled matrix, oil for a carrier/attractant and an active ingredient for the toxicant. Rain would immediately begin breaking down the bait as soon as it hit the ground. In addition, it is likely that the target pest would not be active during the rain. By the time the target pest was out foraging again, the bait would have lost its attractiveness at best, and at worst, may be largely decomposed.

Knowing what to use and when to use it is crucial in solving pest issues. There are several possibilities we can use, like bait or liquid concentrates, aerosols, wettable powders, granular baits and dusts. Repellents and non-repellents have different advantages. How do you pick your mode of action, or the formulation of a pesticide for the pest issue you need to treat?

A few years ago, we may have stocked 15-20 products in our service centers. Now our company’s approved list may contain 10 times as many products. Most service vehicles have 20 or more different pesticides ready for whatever the day may bring. Which chemistry do I need? Where do I start to decide which of those materials I should use on a particular job?

PLAN OF ATTACK. The first question should be whether the pest is flying or crawling. Yes, many pests do both, but I am looking for its predominate mode of travel. Also, what is the point it may enter the structure? Let’s say this pest is a smokybrown cockroach. In the natural environment, it may be on the ground foraging in leaf litter or bushes. It often takes flight at night when lights are on inside and outside of the structure. While flying toward the light, it occasionally enters, or drops, near a door or window of a building.

For this pest, I want to start with a repellent insecticide barrier to intercept it as it walks toward an entry point. A long-lasting repellent insecticide (a material with rapid effects that will either kill or “repel”) is my choice, but I still have the flying entry threat. One consideration here is how much of a barrier I can create. Pyrethroid label restrictions limit the application placement and distance from the structure of many repellent insecticides. Still, no matter how well I may treat the perimeter, if this roach takes flight while the window or door is open, it can sail right over my perfect barrier, landing home free on the kitchen table. So, going to the natural habitat or harborage on a seek and destroy mission is necessary. When found, I can choose my option for how to best eliminate it.

What will give me the most complete coverage of the smokeys in the harborage? Most of the time, a scatter, granular-type bait will give me the best results (as long as it is not raining), but many of my colleagues have had great success with a direct application of a properly labeled liquid insecticide.

Ants are my favorite pest to manage, but the biology, habits and multiple control methods of ants present challenges for new technicians. Multiple-queen colonies that bud when threatened present the biggest challenge. A repellent chemistry may create enough of a threat to cause the colony to split. I have watched this many times with fire ants. A couple of months after a surface mound treatment with a repellent, you can easily have three or maybe five new mounds near the original — now abandoned — mound. A bait or trail treatment with a non-repellent liquid appropriately labeled for this use will take a little longer, but have a much more complete control effect.

Different ant species have so many different habits that some react best to baits, some react quickly to a repellent and non-repellent dual-action pesticide, and some react best to strict non-repellent applications. You also can use repellents to create a barrier at entry points, keeping the pest out of living spaces while the other products do their job.

UNDERSTANDING PESTS.The bottom line is that we have to study pest biology, habits and control strategies both in the volumes of reference material we have, and in the field. We must look at the particular pest within the particular environment we need to effect control. Many times, we encounter different combinations of pests and environments on a job that we have not seen before. When that happens, we have to develop a method to control the pest that is safe to all in close proximity, but is also effective. Knowing the pest identification and how it survives is the starting place to developing the best control strategy.

After understanding the pest we need to control, we must stay current on knowing how various pesticides work. This takes research time, which we need to invest in if we are going to be able to formulate a plan. The manufacturers do a good job of putting out research data and technical bulletins, especially on the new products they bring to market. The research and technical bulletins are valuable in helping us to understand how the product works. Studying the labels tell us how the product can be used based on the manufacturer’s research and testing. Reading and studying the pesticides you have now, or are considering using in the future, is the first step in understanding these control tools.

Being ready to make a decision on a particular pest in a particular environment you face on your next job is the key to our success. Study, test your research in the field and be ready.

The author is an Associate Certified Entomologist and director of technical services at Gregory Pest Solutions, Greenville, S.C.

Copesan is an alliance of pest management companies with locations throughout North America. To learn more, visit www.copesan.com.