The Ins and Outs of Monitoring for German Cockroaches

Dating back to the 1940s, German cockroaches have been one of the most challenging urban pests that PMPs encounter, reminded Mark “Shep” Sheperdigian of Rose Pest Solutions at the recent Purdue Pest Management Conference. In the late 1980s, with the development of very effective baits, the tide turned.

For a period of time, baits seemed like the proverbial “silver bullet.” But German cockroaches proved equal to the task, developing aversion to baits, which caused manufacturers to develop new matrices and pest management professionals to adopt the practice of rotating different baits.

Today, pest management professionals continue to treat with baits using a rotation strategy. They also have at their disposal a variety of other effective tools, including monitors, which Sheperdigian encouraged all attendees to use to their fullest potential.

Insect Sticky Traps (ISTs), Inspection & Monitoring. Baits and dusts are some examples of control efforts used in the early days, Sheperdigian said. PMPs eventually moved to contact residual insecticides, and dusts were inevitably added back into the lineup throughout the 80s. In modern day control, new bait technology was a gamechanger, but cockroach aversion has changed the game again.

The German cockroach just keeps coming back. “If you don’t have a product that can kill all the cockroaches and make it look easy, you have to go back to the fundamentals,” Sheperdigian said. “Whatever your control method of choice is going to be, proper placement is the key.”

Insect Sticky Traps (ISTs) serve four functions: Determining size and scope, tracking activity (population growth and decline), indicating elimination and early detection of re-infestation.

Insect monitors help you characterize the population, this is how big (size) and wide (scope) the problem is.

As visible as some of them may be, German cockroaches rely on their ability to hide to stay out of harm’s way. “Cockroaches spend the vast majority of their time sitting in their harborages, biding their time, but are they doing nothing?” Sheperdigian said. “Unless the population is spilling over the edges, you can never be really sure how big it is.”

But are these efforts working? PMPs need to set out enough traps to determine how far they go by numbering traps, recording trap catch and plotting numbers on a floorplan. Sheperdigian said it doesn’t have to be complicated.

“The numbers you use aren’t science,” he said. “They are simply set to mark where the cockroaches are the worst. This is how you know where to place controls.”

Tracking activity gives you a clearer picture on whether the population is going up or down. You’re going to want to know if your control measures are working, Sheperdigian said, adding, “sometimes you can see success in some areas and failures in others.”

ISTs in conjunction with inspection give the clearest picture of the population, tracking long term activity on if the monitors are working correctly and indicating full elimination.

“Employees will tell you ‘They’re all gone,’ long before they are really all gone, and insect monitors will know when they’re truly all gone,” Sheperdigian said. “There are always one or two left, and it can drag out a lot longer than you think.”

Indicating population extinction signals to a PMP when cockroach populations are completely knocked out. “The employees will stop seeing cockroaches long before the traps go silent,” Shep said. “Monitors will always be the last ones to find the cockroaches.”

Early detection for reinfestation gives a PMP the opportunity to tell the client they’ve had a reinfestation before they know it’s happened.

The principles of using ISTs. Sheperdigian said there are some very basic rules of thumb to keep in mind when placing monitors. Use big monitors for big populations, like low-income housing or badly infested apartments. Put out insect monitors and return to take a look at them; they are going to tell where the infested units are.

This allows PMPs to evaluate the least- to most-infested units effectively. Little monitors can be used for accounts like restaurants because they’re easier to hide, far less expensive and can be placed all over, Sheperdigian said.

“If you’ve got little monitors out and they’re all full, that doesn’t tell you anything,” he said. “If you’ve got three or four little monitors out, you aren’t painting any pictures. That’s not going to get you [results].”

Don’t skimp on the number monitors used. “They’re not expensive, but callbacks are,” Sheperdigian said. Replace all your monitors at the same time and record the number caught. Use enough to see the entire area of infestation and then some, he added.

“It will be worth the effort to record the number of adults and nymphs separately,” Shep said. “You can note male and females. Gravid females will seclude themselves while they develop egg cases. Once they drop the egg cases, the females forage for food.”

When you have a lot of monitors out, the more often you will have some that will disappear for a while and show up later. If you date each monitor, you will be happy you did so, Sheperdigian said.

“Talk to the people who are there every day and come in first thing in the morning,” Sheperdigian said.  “Their information is the best way to start putting your monitors in place.”

Focus on primary harborage sites, but don’t ignore secondary and tertiary harborages. Wood absorbs odors, cockroaches are tightly tied to water and favor warmer environments, Shep said. “Primary harborages are the best places in the account for German cockroaches to be,” he said. “It may not have all the items on their list; it may just be the place with the most items.”

Follow up until you win, said Sheperdigian. “One of the most common mistakes is quitting too soon. This is a typical curve for elimination of cockroaches. It may be longer or shorter, but an efficient program has this shape,” he said.

Following up on the infestation could be assessing progress and considering adjustments, like changing baits or dusting voids.

“ISTs keep you from working blind,” Shep said. “The more you know about the population, the more efficient you will be achieving elimination. A sustained effort guided by well-placed monitors yields the most efficient control.”