German cockroaches can be eliminated from the most-infested multi-unit housing units by taking an assessment-based approach, using an appropriate amount of gel bait as the only means of control, and not requiring residents to clean up or prepare their apartments before treatment.
“We have had miraculous results where we’ve basically gone from summer cockroach trap counts of 800 to 1,000 cockroaches in a single night to one or zero,” said Virginia Tech Entomologist Dr. Dini Miller, who led the study at low-income housing units in Richmond and Hopewell, Va., and Rocky Mount, N.C. All three complexes were under different contracts for professional pest control at the time of the study, which took place from May 2017 to September 2018.
A NOVEL APPROACH
A big part of the study protocol was assessing the level of the cockroach infestation in each unit overnight using large (Lo-Line style) sticky traps. The trap catch determined how much gel bait Miller applied in each unit.
An apartment with a trap count of one to 50 cockroaches got 7.5 grams of bait (a quarter of a tube). A count of 50 to 100 cockroaches got 15 grams (half a tube of bait), and a count of more than 100 cockroaches received 30 grams (one tube) of bait. If the overnight trap catch was more than 500 cockroaches, she applied 60 grams or two tubes of bait. What was particularly unique about putting out these large amounts of bait was the way they were applied.
Lines of bait were applied diagonally to 2-inch-by-2-inch squares of wax paper that had been pre-folded in half into triangles. The folded wax paper was then left open at a 90-degree angle to give cockroaches easy access. Several wax paper packets were placed in each cabinet, behind the stove and refrigerator, underneath the microwave and even slipped into stacks of mail where the cockroaches were harboring.
“We have had miraculous results where we’ve basically gone from summer cockroach trap counts of 800 to 1,000 roaches in a single night to one or zero.” Dr. Dini Miller, Professor of Entomology, Virginia Tech University
The wax paper squares not only let Miller put bait in hard-to-treat places (e.g., within stacks of clutter) but it gave the pests a ‘clean dinner plate’ when surfaces were dirty, covered in food debris or contaminated by old bait or repellent spray. The cockroaches weren’t deterred by the wax paper — they ate right through it — and Miller was able to easily remove any bait residues that were not consumed by the insects.
Within 60 days, Miller achieved a 90 percent reduction in trap catch in the Richmond units, even in June with summer cockroach populations actively growing. She continued to trap one or two cockroaches in units for some time after the initial knockdown, treating these as low-level infestations.
Miller assessed units monthly over 16 months and found that cockroach populations did not rebound the next summer. “It looks like once they’re gone, they’re actually gone,” she said of the pests. “We still had some units where we still (caught)one or two cockroaches, but at this same time last year, we caught 1,000 cockroaches in a single night.”
THE POWER OF ROTATION
The study also documented the results of bait rotation, which can help prevent bait aversion and insecticide resistance in German cockroach populations.
Bait aversion is when cockroaches develop a dislike for certain sugars or food ingredients in the bait matrix. “I love pizza but if you feed me pizza every day for five years, I’m going to quit eating it; cockroaches are the same way,” explained Chris Keefer, technical services manager for Professional Pest Management at Syngenta, North America.
Resistance, on the other hand, is a physiological response: the cockroach can digest an active ingredient and it is no longer effective on the pest. Cockroaches in public housing facilities have “very malleable genetics” and using the same control products year after year contributes to this problem, said Miller. “We need to avoid resistance like the plague,” she said.
In the study, Miller rotated the use of Advion Evolution Cockroach Gel Bait and Optigard Cockroach Gel Bait every three months at the 30 apartments in Rocky Mount. The Syngenta baits delivered effective control: The units saw “a total wipeout” of the cockroach population with none caught in follow-up traps through June; “that’s huge,” Miller said.
“Syngenta launched Advion Evolution and Optigard Cockroach together last summer, which along with the original Advion Cockroach Gel Bait, means we’ve got three very compatible baits that can be used in rotation to combat aversion and insecticide resistance,” said Nicky Gallagher, technical services manager for Professional Pest Management at Syngenta, North America.
“I love pizza but if you feed me pizza every day for five years, I’m going to quit eating it; cockroaches are the same way.” Chris Keefer, Technical Services Manager for Professional Pest Management at Syngenta, North America
Advion Evolution has the same active ingredient – indoxacarb – as the original Advion Cockroach, but it has an enhanced bait matrix. Even cockroach strains known for being bait averse will “binge feed” on it and the higher consumption is leading to a faster kill by many days in some situations, said Gallagher.
Indoxacarb works in a unique way: the insect first must ingest it; then the insect’s own internal enzymes change the active ingredient’s molecular structure, converting it to the more powerful MetaActive™ technology that attacks the cockroach’s nervous system.
Mammals and other non-target organisms don’t have the same digestive enzymes, which makes indoxacarb a good fit for sensitive accounts like restaurants and food-handling facilities.
And it provides “exponential control” of cockroaches as the pests can also get a lethal secondary or tertiary dose of the active ingredient by feeding on the feces, exudates or dead bodies of cockroaches that previously consumed a lethal dose, said Gallagher.
Optigard Cockroach works differently. It contains emamectin benzoate, which targets two areas in the insect – the neuro and muscular systems. “Targeting two areas, not just one, is absolutely better because this makes it much more difficult for the insect to potentially develop resistance to the active ingredient,” according to Keefer.
“Syngenta launched Advion Evolution and Optigard Cockroach together last summer, which along with the original Advion Cockroach, means we’ve got three very compatible baits that can be used in rotation to combat aversion and insecticide resistance.” Nicky Gallagher, Technical Services Manager for Professional Pest Management at Syngenta, North America
A NO-PREP APPROACH WORKS
In the study, Miller did not ask residents to clean up or disturb their cockroaches in any way before treatment, such as by emptying cabinets and removing clutter, and still “the effect has been amazing,” she said. “We do not disturb the cockroaches in any way, instead we offer them dessert while they are lounging in their harborages. We want our cockroaches relaxed and hungry!
“There are a million reasons why the residents need to clean up but cockroach control is not one of them,” added Miller. “Blaming residents’ behavior is an excuse; one that all of us have used for 50 years,” she said. “But we really do have the power to control cockroaches. Let’s use it!”
It is possible for pest management professionals to follow this assessment-based protocol in the field and keep costs in check, according to Miller, who has specific tactics on how to achieve this ambitious goal.
“Let’s try something totally different” because the current approach to cockroach control in low-income, multi-unit housing is not working, she said.
Syngenta is committed to helping pest management professionals in this effort. “Even after launching Advion Evolution and Optigard Cockroach, we’re still going to continue working on other cockroach solutions,” said Gallagher. “Syngenta is a research-driven company and we have a really good pipeline of products in development,” she said.
“Syngenta has proven it is a dedicated leader in cockroach control by the products it continues to introduce and the training and support it brings to the pest management industry,” added Keefer.
To learn more about any of the products and services featured in this article, contact your Syngenta territory manager or visit SyngentaPMP.com.