Webinar Title: Cockroaches
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: awaiting team confirmation]
Scope note. This file is the cockroach hour of a longer broadcast. Dr. Suiter closes at “It’s about four o’clock” and hands back to the moderator; the ant segment that followed is not part of this recording or this archive package.
NARRATIVE SUMMARY
Dr. Dan Suiter, Extension Entomologist at the University of Georgia, spent the first eight minutes on Entomological Society of America credentials, including the Certified IPM Technician program the ESA had launched the week before for technicians with as little as one year of experience and no license requirement beyond state registration. He then turned to the roughly 5,000 cockroach species worldwide and to the Southeast, where diversity runs highest and thins out going north and west.
The scientific core of the hour is nitrogen. Every other insect flushes excess nitrogen out as uric acid; cockroaches keep it. They store it in fat body cells called urocytes, sitting beside mycetocytes that house a bacterium found nowhere on the globe except the cockroach gut. When the roach starves, the bacterium breaks that stored uric acid back into usable nitrogen. This is why a German cockroach given only water lives more than a month and an American cockroach lives three, and why the large peridomestic roaches, permanently half starved for nitrogen, take bait so readily. Suiter followed the same chemistry into gout and allopurinol, a human drug his lab at the University of Florida fed to cockroaches. It killed them by letting precursors build to levels they had never encountered, the university patented the use, and it turned out far too slow to sell.
The second half is field material. Peridomestic species want warm, humid, dark, still air: tree holes, hollow block walls, soffits, and attics with a leaking pipe penetration, which Suiter illustrated with the half inch of smoky brown frass that fell on him in his own 1957 house. He argued for granular bait over a residual spray outdoors, because the spray also kills the tiny wasps that sting roach egg cases, and about half the capsules in his Florida study had been stung. He described the quart paint can trap baited with beer-soaked white bread, the graduate student who killed whole fire ant colonies by feeding them roaches killed with indoxacarb, and finally German cockroach reproduction: a female mates once, is gravid for about 75 percent of her adult life, and during those 27-day stretches does not eat, drink, or move. Kill males all you like. Reaching her means aerosols in screw holes and bait in cracks.
YOUTUBE 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 & 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.
ADDITIONAL RESOURCES
- 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 connect callers 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: Corrected SRT (Stage 1) — GTBOP_Transcript_2021-11-10_Cockroaches.srt (741 blocks)