Webinar Date: November 10, 2021
Speaker: Dr. Dan Suiter, Extension Entomologist, University of Georgia
Moderator: addressed on air as “Richie”; not captioned
Duration: 54:51
Series: Structural Pest Control
CEU Categories: Pending confirmation. Check with the UGA Center for Urban Agriculture before claiming credit.
This recording is the cockroach hour of a longer broadcast. Dr. Suiter closes at about four o’clock and hands back to the moderator; the ant segment that followed is not part of this archive.
About This Session
Dr. Dan Suiter spent the opening eight minutes on Entomological Society of America credentials, then gave the rest of the hour to cockroach biology and the field practice that follows from it. The credentialing segment is worth knowing about on its own: the ESA had launched the Certified IPM Technician program the week before, aimed at technicians with one year of experience and no license requirement beyond state registration, alongside the older ACE program that has produced about 1,300 Associate Certified Entomologists worldwide since 2004.
The biology turns on one fact. Every other insect takes in more nitrogen than it can use and flushes the excess out as uric acid, the white in bird droppings. Cockroaches keep it. They pack it into fat body cells called urocytes, and beside those sit mycetocytes holding a bacterium that occurs nowhere on the globe except the cockroach gut. When the roach starves, that bacterium breaks the stored uric acid back into usable nitrogen. Suiter traced the behavior back to the tropical forest floor, where dead animals are rare and a cockroach that finds one should not waste what it cannot use immediately. The consequences are practical: a German cockroach given water and no food lives more than a month, an American cockroach lives three, and the white material that comes out of a squashed American roach is stored uric acid, which Suiter called gold to a cockroach. The system is obligatory. Feed a roach nothing but high protein and it cannot stop making uric acid; its gut nearly bursts packing it in.
The same chemistry runs through people. Gout is uric acid crystallizing into knife-like slivers around the toes and ankles, and allopurinol treats it by stripping out the enzyme that converts the precursor into uric acid. Suiter’s group at the University of Florida gave allopurinol to cockroaches and killed them, because the precursors built up to levels the insects had never encountered. The university patented the use, one bait was commercialized with oxypurinol as the active ingredient, and it proved far too slow to compete.
From there the session is field material. The large peridomestic roaches want the same four things everywhere they harbor: warmth, humidity, darkness, and still air. Tree holes, crawl spaces, hollow block walls, soffits, rotted cross ties, and attics with a leaking pipe penetration, which Suiter says is ecologically the same thing as a big tree hole. His own house, built in 1957, taught him that lesson directly when he pulled down a bathroom ceiling during renovation and half an inch of accumulated smoky brown frass came down on him. He counted 150 smoky browns on one set of granite steps at night and 100 coming out of one block wall. He is against filling tree holes, on the grounds that it creates more harborage rather than less.
His argument for granular bait over a residual spray outdoors rests on the parasitoid wasps. A wasp about a sixteenth of an inch long finds a cockroach egg case by the odor it gives off, from as far as 20 feet, stings it, and lays 80 eggs inside; the young eat the developing roaches and chew their way out together. Roughly half the egg cases Suiter’s Florida study recovered had been stung. A pyrethroid microcap sprayed on a wall or a tree hole kills those wasps along with the roaches, while a handful of granular bait leaves them working and stays available far longer. He put out a liquid residual in an ant trial one summer and got five inches of rain two nights later. He also warns that any bait program gets a second wave, because the egg capsules incubate 40 days.
For sites where no pesticide is acceptable, Suiter described the quart paint can trap: mineral oil and Vaseline mixed one to one around the inside lip, cheap beer soaked into white bread in a screened cup at the bottom, and the can set against a wall. Seventy-five adults in one can overnight is achievable. The German cockroach version uses a baby food jar with dog food or banana.
The session ends on German cockroach reproduction, which is where the control argument lands. A female mates once and gets six or seven egg cases from it. Each cycle is about 10 days free, when she does nearly all her eating, drinking, and moving, and about 27 days gravid, when she backs into a harborage such as a hollow stool leg and does not eat, drink, or move at all. That puts her at roughly 75 percent of her adult life pregnant and far harder to kill. Killing males accomplishes nothing, since she only needed one. Suiter’s comparison is deer management in Georgia, where DNR allows 12 does and two bucks. The practical conclusion is the oldest one in the trade: inspect thoroughly, get aerosols into screw holes and popping tops, get bait into cracks and crevices, and as he put it, if you are not on your back looking behind things with a flashlight, you are not doing it right.
Chapters (Video Timestamps)
0:00 Welcome: cockroaches of the Southeast
1:54 ESA credentials: ACE, BCE, and the new CIT
7:39 Food and water: surviving on water alone
10:20 Nitrogen, uric acid, and the cockroach fat body
17:42 Gout, allopurinol, and a patented use
20:52 Peridomestic roaches and the true palmetto bug
23:48 Harborage: warm, humid, still, and dark
26:29 Half-starved roaches, bait, and egg case wasps
29:27 Smoky brown roach: egg capsule to first instar
31:35 Tree holes, soffits, and block wall voids
36:05 American roaches, sewers, and the old bait pastes
41:48 The paint can trap: mineral oil, beer, white bread
44:26 Gel bait in the field, and fire ant secondary kill
47:10 German roaches: food and water are never limiting
49:22 Reproductive biology: gravid 75% of adult life
53:59 Crack and crevice, and the flashlight test
Questions and Answers
Q: How long can a cockroach actually survive with water but nothing to eat?
A: A German cockroach lives more than a month on its fat body reserves. An American cockroach lives three months. Reverse it and give them food but no water and they last just short of two weeks, about the same as complete starvation. Suiter put the water-only figures in bed bug territory, since bed bugs go two or three months without a blood meal.
Q: What is the white stuff that comes out when you step on an American roach?
A: Uric acid stored in the fat body. Suiter called it “gold to a cockroach.”
Q: Why are the large roaches so easy to bait?
A: They are half starved for nitrogen. Cockroaches are the only insects that hold onto excess nitrogen instead of excreting it, so they forage constantly for it. Suiter’s illustration is a manhole cover where a car runs over a group of American roaches; a few minutes later the antennae come back out and the survivors eat the squashed ones, going straight for the uric acid.
Q: What breaks the stored uric acid back down so the roach can use it?
A: A bacterium that occurs only in the cockroach gut, housed in a fat body cell called a mycetocyte next to the urocyte where the uric acid sits. Under starvation it converts the uric acid to usable nitrogen. The system is obligatory, and Suiter noted that a roach fed nothing but a high-protein diet cannot stop making uric acid; its gut nearly explodes packing it in.
Q: What conditions should I be inspecting for when I look for the large peridomestic roaches?
A: Warm, humid, dark, and no air movement. That means tree holes, attics, crawl spaces, soffits, hollow block walls, and rotted cross ties. Suiter’s framing is that an attic with a leaking pipe penetration is the ecological equivalent of a big tree hole, and in the South, pipes penetrating an attic will eventually leak.
Q: Why pick a granular bait over a residual spray for outdoor roach work?
A: A pyrethroid microcap on a wall or a tree hole will work, but it also kills the parasitoid wasps that sting cockroach egg capsules, and about half the capsules Suiter’s Florida study recovered had been stung. Granular bait leaves those wasps working and stays available far longer. He put out a liquid residual in an ant trial one summer and got five inches of rain two nights later.
Q: I baited and knocked the population down. Why did roaches come back weeks later?
A: The egg capsules incubate for 40 days. The first application kills the adults, and then a second wave arrives when those capsules hatch.
Q: Should I fill in a tree hole to stop the roaches living in it?
A: Suiter does not recommend it. Filling the hole creates more harborage space around it rather than less. He would rather put a handful of granular bait up in the hole. One tree hole he photographed in Athens was producing 50 smoky browns a night.
Q: How do I knock a large roach population down at a site where the customer will not accept pesticides?
A: A quart paint can from a hardware store with the inside lip coated in mineral oil and Vaseline mixed one to one. Soak white bread in cheap beer, put it in a small cup, screen over the top, set the cup in the bottom of the can, and place the can against a wall where roaches have been seen. Suiter has caught 75 adults in one can overnight, then finished them with hot soapy water and reused the can. For German roaches, use a baby food jar with Vaseline inside and dog food or a piece of banana as the attractant. Always against a wall, never out in the middle of the floor.
Q: Does killing roaches outdoors with gel bait do anything to fire ants?
A: Yes. In the South, fire ants are among the first things to arrive on a pile of dead insects. A graduate student in Suiter’s lab collected roaches killed by indoxacarb and fed them to fire ant colonies, killing entire colonies, because activated indoxacarb was still in the cockroach. The dead roach becomes a fire ant bait.
Q: Why does it matter that a German cockroach female is gravid most of her life?
A: She mates once and gets six or seven egg cases out of it, then dies of old age. Each reproductive cycle runs roughly 10 days free and 27 days gravid, which puts her at about 75 percent of her adult life pregnant. During the gravid stretch she backs into a harborage, often a hollow stool leg, and does not eat, drink, or move. Across the cycle she is in harborage about 90 percent of the time, visits food and water less often, and consumes less when she gets there. That is when she is hardest to kill.
Q: If the females are that hard to reach, where does treatment need to go?
A: Into the cracks and crevices where she harbors. Aerosols into screw holes and popping tops, bait into cracks. Killing males does nothing to the population, since the female only has to mate once. Suiter’s analogy is deer hunting in Georgia, where DNR allows 12 does and two bucks, because reducing an animal population means reducing the female population.
Resources
Referenced in the presentation:
- entsoc.org: Entomological Society of America certification programs. ACE (Associate Certified Entomologist, started 2004, about 1,300 worldwide), ACE International (launched 2014), Board Certified Entomologist, the Public Health Entomology Certificate, and the Certified IPM Technician launched November 2021. Suiter offered to put callers in touch with the ESA staff member overseeing the programs.
- Cockroaches of the United States: a review by Tom Atkinson published by the Entomological Society of America, mapping the distribution of US cockroach species. Suiter noted it comes up on a search for “cockroaches of the US.”
- National Geographic, “cockroaches of the world”: a photo feature Suiter cited from memory as showing tropical cockroaches as striking as any swallowtail butterfly.
Processed for UGA Center for Urban Agriculture / GTBOP Archives
Source: Stage 2 Archive Package — GTBOP_Archive_Summary_2021-11-10_Cockroaches.md