Use ULV wisely when targeting German cockroaches

Two German cockroaches enjoy a cookie with pineapple filling. (PHOTO: SMUAY / ISTOCK / GETTY IMAGES PLUS)

Large-area space treatment with an ultra-low volume (ULV) machine for cockroach control became commercially viable in the mid-1970s. In the summer of 1964, though, as a graduate student at Purdue University, I was assigned to help a professor test a machine in an open field of oats for cereal leaf beetles (Oulema melanopus).

I stood in the middle of the field with a glass plate strapped to each arm to catch the droplets. An airplane flew over me and applied a ULV application of pesticide. I thought I would get soaked, but it took just 1 ounce of liquid pesticide to cover an entire acre.

Years later, I used this same technique to control German cockroaches (Blattella germanica) in a restaurant. It was the thrill of the kill. Cockroaches came running out, then dropped like raindrops. The problem with ULV, however, is that it also chases them in all directions — where some escape and the population becomes more difficult to reach and eliminate.

Harvesting cockroaches is not how you measure success. Success is measured in how many you leave that can rebound. You want to eliminate the population, not keep harvesting cockroaches.

ULV is still effective, however, if you can confine the area you want to treat with a large plastic sheet, like a painter’s drop cloth. What follows are two situations where treatments initially failed and why.

Prepping offers pests protection

I helped troubleshoot a German cockroach account for a pest management professional (PMP) in Brooklyn, N.Y. He was using a ULV treatment in a small restaurant every week, and it was not working. Why? The PMP told the restaurant owner to cover the dishes and food preparation areas before he came in to treat. The staff covered everything with drop cloths — which protected the cockroaches.

• Solution: Confine the ULV treatments to areas under the drop cloths. Clean everything before opening the restaurant. Better yet, switch to baiting and dusting. Then, monitor with sticky traps to see where more work is needed.
• Conclusion: Properly communicating with a customer on how to prep a job is very important. Using ULV without proper preparation can be a disaster.

Cockroaches know when to leave and when to return

A mega-population of German cockroaches in another New York restaurant was nowhere near under control. The PMP I was called in to troubleshoot for was treating the space with a residual before turning to a ULV treatment.

It was wintertime, and the outdoor temperature was about 20 degrees Fahrenheit. I watched him treat, and everything seemed to be correct.

When we finished, he told me I could go back to the truck while he got the service slip signed. The truck was locked. I was cold. To block the wind, I went over to stand between a garbage dumpster and the back wall of the restaurant’s kitchen.

That’s when I saw German cockroaches trickling out into the cold from the interior. Ten, 50 and then hundreds of healthy cockroaches appeared. They escaped the treatment, waited outside, and went back inside when it was safe to do so.

• Solution: We treated the area from the exterior with dust and sealed the opening.
• Conclusion: Cockroaches will do what they must to survive — even if it means being cold for a little while.

<p>The post Use ULV wisely when targeting German cockroaches first appeared on Pest Management Professional.</p>

from Pest Management Professional https://www.mypmp.net/2025/02/11/use-ulv-wisely-when-targeting-german-cockroaches/
Sacramento CA